áþNSACLASSNNSAMODCCLASSNMAP_UNITC SOURCECUNIT_NAMEC|DESCRIPTIOCþAGEC>FOSSILCþRADIOMETRICþQUADRANGLECROCK_CLASSCQCLASSNLABELC 98 98 unmapped LC002Unmapped High mountain area shown as unmapped in eastern central part of quadrangle Lake Clark 98 534 unmapped LC005Unmapped Areas of apparent bedrock in lowlands as inferred from air photos. Scoured by glaciers and may have thin surficial cover. Lake Clark 2750 99 5099 bu DI005Possible bedrock of unknown character Areas that air photo interpretation suggest as being underlain by bedrock. Typically are of higher elevation than surrounding glacial deposits and show hints of structure. In one case, an apparent strike and dip of bedding is perceptible on air photos.Unknown Dillingham Sedimentary 99 bu 99 705 JQu KN007Glacial deposits and volcanic and plutonic rocks, undivided Glacial deposits and volcanic and plutonic rocks, undivided Quaternary, Tertiary to Jurrassic Kenai Igneous 99 99 899 bu KN008Possible bedrock of unknown character Areas that air photo interpretation suggest as being underlain by bedrock. Typically are of higher elevation than surrounding glacial deposits and show hints of structure. In one case, an apparent strike and dip of bedding is perceptible on air photos.Unknown Kenai Sedimentary 99 bu 99 599 bu LC005Possible bedrock of unknown character Areas that air photo interpretation suggest as being underlain by bedrock. Typically are of higher elevation than surrounding glacial deposits and show hints of structure. In one case, an apparent strike and dip of bedding is perceptible on air photos.Unknown Lake Clark Sedimentary 99 bu 99 600 ? LC006Bedrock? of unknown character Areas on Wes Wallace field compilation that are shown with "?" Unknown Lake Clark 99 bu 99 599 bu TA015Undifferentiated bedrock Areas of apparent bedrock or areas of known bedrock that appear different than surrounding outcrops. In some cases, this will be areas in otherwise surficial deposits that show unusual high relief or possible bedding. In areas of known bedrock, this ma Taylor Mountains 99 99 1999 bu TA019Undifferentiated bedrock Areas of apparent bedrock or areas of known bedrock that appear different than surrounding outcrops. In some cases, this will be areas in otherwise surficial deposits that show unusual high relief or possible bedding. In areas of known bedrock, this ma Taylor Mountains 99 100 163 Qu DI002Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Dillingham Unconsolidated1000Qs 100 5100 Qu DI005Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Dillingham Unconsolidated1000Qs 100 105 Qs IL002Surficial deposits Unsorted to well-sorted alluvial, colluvial, glacial, glaciofluvial, lacustrine, marine, and eolian deposits Quaternary (Holocene and Pleistocene) Iliamna Unconsolidated1000Qs 100 100 Qs IL006Surficial deposits Unsorted to well-sorted alluvial, colluvial, glacial, glaciofluvial, lacustrine, marine, and eolian deposits Quaternary (Holocene and Pleistocene) Iliamna Unconsolidated1000Qs 100 800 Qcaf IL008Colluvium, alluvium, lacustrine, and floodplain deposits Colluvium, alluvium, lacustrine, and floodplain deposits Quaternary (Holocene) Iliamna Unconsolidated1000 100 100 Qs KN002Surficial deposits Surficial deposits Tertiary (Eocene and Paleocene?) Kenai Unconsolidated1000Qs 100 100 Qs KN003Surficial deposits Surficial deposits Tertiary (Eocene and Paleocene?) Kenai Unconsolidated1000Qs 100 707 none KN007Drift River delta Drift river delta, no description Quaternary (Holocene) Kenai Unconsolidated1000 100 800 Qs KN008Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced, deposited, and reworked by action of wind, water, glaciers, and frost, including solifluction. In many areas of the map, this unit is a mixture of surrounding surficial deposit units that could not be reaQuaternary Kenai Unconsolidated1000 100 900 Qs KN009Quaternary surficial deposits Undivided surficial deposits Quaternary Kenai Unconsolidated1000 100 1100 Qcaf KN011Colluvium, alluvium, lacustrine, and floodplain deposits Colluvium, alluvium, lacustrine, and floodplain deposits Quaternary (Holocene) Kenai Unconsolidated1000 100 1201 Qs KN012Quaternary Unconsolidated deposits Quaternary Kenai Unconsolidated1000 100 111 Qu LC002Moraine, till, glacial outwash, alluvium, and colluvium, undivided Terminal and lateral moraines of alpine glaciers, ground moraine and bedrock cored drumlins. Widespread outwash. Quaternary Lake Clark Unconsolidated1000Qs 100 500 Qu LC005Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Lake Clark Unconsolidated1000Qs 100 617 Q LC006Quaternary and unmapped Undivided Quaternary deposits and unmapped areas. Quaternary Lake Clark Unconsolidated1000Qs 100 1200 Q LC012Alluvial, colluvial, and glacial deposits Alluvial, colluvial, and glacial deposits Quaternary Lake Clark Unconsolidated1000 100 82 Qs SV002Surficial deposits Surficial deposits Tertiary (Eocene and Paleocene?) Seldovia Unconsolidated1000Qs 100 500 Qcaf SV005Colluvium, alluvium, lacustrine, and floodplain deposits Colluvium, alluvium, lacustrine, and floodplain deposits Quaternary (Holocene) Seldovia Unconsolidated1000 100 170 Qu TA002Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Taylor MountainsUnconsolidated1000Qs 100 3170 Q TA003Quaternary deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. (Added, not in source) Quaternary Taylor MountainsUnconsolidated1000Qs 100 4170 Q TA004Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Taylor MountainsUnconsolidated1000Qs 100 5170 Q TA005Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Taylor MountainsUnconsolidated1000Qs 100 901 Q TA009Surficial deposits Includes flood plain, glacial, silt, and gravel deposits. Quaternary Taylor MountainsUnconsolidated1000Qs 100 1001 Q TA010Surficial deposits Includes flood plain, glacial, silt, and gravel deposits. Quaternary Taylor MountainsUnconsolidated1000Qs 100 1101 Q TA011Surficial deposits Includes flood plain, glacial, silt, and gravel deposits. Quaternary Taylor MountainsUnconsolidated1000Qs 100 1201 Q TA012Surficial deposits Includes flood plain, glacial, silt, and gravel deposits. Quaternary Taylor MountainsUnconsolidated1000Qs 100 5100 Qs TA015Undifferentiated surficial deposits Mainly unsorted gravel, sand, and silt produced and deposited by action of wind, water, frost, and solifluction. Quaternary Taylor MountainsUnconsolidated1000Qs 100 2001 Qal TA020Alluvial deposits Includes alluvium and glaciofluvial deposits. Alluvium in minor streams not shown Quaternary Taylor MountainsUnconsolidated1000 275 5275 Qsb DI005Glacially scoured possible bedrock of unknown character Areas that air photo interpretation suggest as being underlain by bedrock. Typically are of higher elevation than surrounding glacial deposits and show hints of structure. In one case, an apparent strike and dip of bedding is perceptible on air photos.Unknown Dillingham Sedimentary 2750bu 275 834 Qsb KN008Scoured bedrock Glacially scoured bedrock; may be covered with thin glacially derived deposits; air-photo interpretation. Quaternary Kenai Unconsolidated2750 275 534 Qsb LC005Scoured bedrock Glacially scoured bedrock; may be covered with thin glacially derived deposits; air-photo interpretation. Quaternary Lake Clark Unconsolidated2750 275 5341 Qsb LC005Scoured bedrock Glacially scoured bedrock; may be covered with thin glacially derived deposits; air-photo interpretation. Within area of scoured bedrock, appears to be different bedrock. Quaternary Lake Clark Unconsolidated2750 275 Q 5275 Qsb TA015Scoured bedrock Areas of apparent bedrock covered by thin(?) surficial deposits. Varies Taylor MountainsUnconsolidated2750 300 190 Qv IL002Volcanic rocks, undivided Lava flows and associated pyroclastic rocks associated with Iliamna Volcano Quaternary Iliamna Igneous 3000Qv 300 191 Qal IL002Augustine Volcanics -- Lava flows Lava flows, chiefly hypersthene-augite andesite and minor dacite and rhyolite on Augustine Volcano. Quaternary (Holocene and Pleistocene) Iliamna Igneous 3000Qv 300 300 Qv KN002Volcanic rocks Lava, breccia, and associated pyroclastics. May include Tertiary volcanic rocks Quaternary (with mixed Tertiary?) Kenai Igneous 3000Qv 300 704 Qv KN007Volcanic rocks of Redoubt Volcano Volcanic rocks of Redoubt Volcano Quaternary Kenai Igneous 3000 300 850 Qv KN008Volcanic rocks, undivided Consists of volcanic rocks and deposits associated with Iliamna, Redoubt, and Double Glacier volcanoes. Typically restricted to immediate vicinity of these volcanic centers, however locally, debris flows and air-fall material may be somewhat distal. LoQuaternary Kenai Igneous 3000Qv 300 1202 Qv KN012Quaternary volcanic rocks Volcanic rocks of Iliamna and Redoubt volcanoes Quaternary Kenai Igneous 3000 300 112 Qv LC002Andesitic lava and tuff of Iliamna Volcano Light gray andesitic lava and yellowish-gray, opalized tuff. Quaternary Lake Clark Igneous 3000Qv 300 618 Qv LC006Volcanic rocks Volcanic rocks Quaternary Lake Clark Igneous 3000Qv 300 105 Qv SV002Volcanic rocks, undivided Lava flows and associated pyroclastic rocks associated with Iliamna Volcano Quaternary Seldovia Igneous 300 Qv 305 511 Qil IL007Iliamna Lava flows Light-gray hypersthene-augite andesitic lava, breccia, and associated pyroclastic debris Quaternary Iliamna Igneous 3050Qv 305 808 Qtv IL008Lava flows, North and South Twin volcanic center Lava flows from the North and South Twin volcanic center. Probably andesitic Quaternary Iliamna Igneous 3050 305 511 Qil KN005Iliamna Lava flows Light-gray hypersthene-augite andesitic lava, breccia, and associated pyroclastic debris Quaternary Kenai Igneous 3050Qv 305 855 Hv KN008Holocene volcanic rocks Holocene volcanic rocks, primarily associated with Redoubt Volcano Quaternary (Holocene) Kenai Igneous 3050Hv 305 711 Qil LC007Iliamna Lava flows Light-gray hypersthene-augite andesitic lava, breccia, and associated pyroclastic debris. Quaternary Lake Clark Igneous 3050Qv 305 1055 Qiv LC010Lava flows Lava flows from the present Iliamna volcanic center. Probably andesitic Quaternary Lake Clark Igneous 3050 305 511 Qil SV004Iliamna Lava flows Light-gray hypersthene-augite andesitic lava, breccia, and associated pyroclastic debris Quaternary Seldovia Igneous 3050Qv 305 555 Qtv SV005Lava flows, North and South Twin volcanic center Lava flows from the North and South Twin volcanic center. Probably andesitic Quaternary Seldovia Igneous 3050 310 193 Qap IL002Augustine Volcanics -- Pumice and scoria Pumice and scoria on Augustine Volcano. Quaternary (Holocene and Pleistocene) Iliamna Igneous 3100Qpd 310 1060 Qjgdt LC010Johnson Glacier dome tephra deposits Dome tephra Quaternary Lake Clark Igneous 3100 311 861 Qca KN008Ash-rich colluvium Consists of tephra-rich colluvium in the vicinity of and west of Redoubt volcano. Similar to other volcanoes, these deposits probably consist of ash and larger-sized pyroclasts. On the flank of Redoubt Volcano, these deposits mantle and are incorporateQuaternary (Holocene) Kenai Igneous 3110 312 635 Qls KN006Deposits of Mass Wasting -- landslide deposits Deposits of landslides, including falls, slumps, slides, and failures by lateral spreading. Assigned NSA = 312 in vicinity of Polly Creek where this unit consists of debris flows from Mount Redoubt. Quaternary Kenai Igneous 3120Qls 312 703 Qm KN007Debris flow deposits Debris flow deposits of Crescent River valley. Includes several small (older?) deposits in the upper valley and the 3,500-year-old debris flow in the lower valley Quaternary (Holocene) Kenai Igneous 3120 312 862 Qdfn KN008Debris flow deposits, younger Redoubt flows Debris flow deposits on the north flank of Redoubt Volcano in the Drift River valley Quaternary (Holocene) Kenai Igneous 3122 312 8621 Qdf2 KN008Debris flow deposits, older Redoubt flows Debris flow deposits of North Fork, Crescent River. Deposits of multiple debris flows off the west and southwest flanks Redoubt Volcano. Oldest(?) deposit is derived from west flank of Redoubt. Next oldest deposit appears derived from presently glaciaQuaternary (Holocene) Radiocarbon date of about 3,500 yrs. BP on youngest and most extensive debris flow. Kenai Igneous 3121 312 8622 Qdf1 KN008Debris flow deposits, younger Redoubt flows Debris flow deposits of North Fork, Crescent River. Deposits of the youngest, most extensive, and probably most fluid debris flow derived from southwest flank of Redoubt Volcano. Flow was apparently derived from a presently glacier free valley drainingQuaternary (Holocene) Radiocarbon date of about 3,500 yrs. BP on youngest and most extensive debris flow. Kenai Igneous 3122 312 1162 Ql KN011Lahar deposits Lahar deposits Quaternary (Holocene) Kenai Unconsolidated3120 312 5312 Qdf LC005Debris flow deposits Apparent debris flow deposits of upper Cresecent River valley. Unusual deposits emanating from valley on east side of Crescent River valley. Source valley is along extension of normal fault trending to the northeast and having apparent Holocene motion.Quaternary (Holocene) Lake Clark Igneous 3120 313 192 Qar IL002Augustine Volcanics -- Volcanic rubble and mudflows Volcanic rubble and mudflows on Augustrine Volcano. Quaternary (Holocene and Pleistocene) Iliamna Igneous 3130Qmf 313 706 none KN007Areas in Drift River valley subjected to flood scour or deposition by 1966 floods Areas in Drift River valley subjected to flood scour or deposition by 1966 floods Quaternary (Holocene) Kenai Unconsolidated3130 313 708 pattern KN007Areas on Drift River delta subjected to flood scour or deposition prior to 1966 Areas on Drift River delta subjected to flood scour or deposition in the several decades before 1966 Quaternary (Holocene) Kenai Unconsolidated3130 313 863 Qdr KN008Drift River delta mudflow deposits, undifferentiated Areas of mudflow deposits, not easily separatable into the Younger and Older events Quaternary (Holocene) Kenai Unconsolidated3130 313 8631 Qdr2 KN008Older Drift River delta mudflow deposits Areas of mudflow deposits, tending to be more heavily vegetated and tending to control location of Drift River channels Quaternary (Holocene) Kenai Unconsolidated3130 313 8632 Qdr1 KN008Younger Drift River delta mudflow deposits prior to 1957 Areas of mudflow deposits, tending to be minimally vegetated and relatively close to channel of Drift River Quaternary (Holocene) Kenai Unconsolidated3130 314 801 Qda IL008Debris-avalanche deposits Volcanic avalanche deposits consisting of poorly sorted mixture of angular sand, cobbles, and boulders. All deposits contain clasts of grey andesitic lava and yellow-orange hydrothermally altered rocks. Estimated age is less than 1,000 years and some mQuaternary (Holocene) Iliamna Unconsolidated3140 314 1164 Qav KN011Volcanic avalanche deposits Volcanic avalanche deposits consisting of poorly sorted mixture of angular sand, cobbles, and boulders. All deposits contain clasts of gray andesitic lava and yellow-orange hydrothermally altered rocks. Estimated age is less than 1,000 years and some mQuaternary (Holocene) Kenai Igneous 3140Qva 402 901 Qv KN009Quaternary volcanic rocks Composite dome complex consisting of medium- to coarsely porphyritic hornblende andesite and dacite. Quaternary (Pleistocene) Three K-Ar whole-rock ages, two considered minimum ages at 627 and 763 ka and one of 887 ka. Kenai Igneous 4020 402 1102 Qjgd LC010Johnson Glacier dome complex Dome complex Quaternary Lake Clark Igneous 4020 450 134 QTv IL002Volcanic rocks, undivided Scoriaceous olivine basalt on Seven Sisters and possibly andesite at West Glacier Creek Quaterary or Tertiary (Pleistocene or Pliocene) Iliamna Igneous 4500QTv 460 531 QTi IL007Basaltic andesite porphyry dikes and sills Basaltic andesite porphyry dikes and sills Quaternary and Tertiary Iliamna Igneous 4600QTi 500 110 Ts IL002Sedimentary rocks, undivbided Mainly light- to medium-gray and light-tan, fine- to medium-grained tuffaceous feldspathic to arkosic wacke and siltstone containing scattered pebbles and lenticular beds of pebble conglomerate. Micaceous clay and silt having moderately abundant glass sTertiary (Pliocene or Miocene) Plant debris and carbonaceous material common but largely unidentifiable or nondiagnostic. Picea sp. indicating a possibly middle or late Tertiary age. Iliamna Sedimentary 540 540 Tks KN002Sterling Formation Sandstone, siltstone, and some coal Tertiary (Pliocene and Miocene) Kenai Sedimentary Tsf 540 80 Ts SV002Sterling Formation Interbedded, weakly lithified sandstone, siltstone, mudstone, carbonaceous shale, lignite coal, and minor volcanic ash. Tertiary (Pliocene and Miocene) Seldovia Sedimentary Tsf 545 78 Tb SV002Beluga Formation Interbedded, weakly lithified sandstone, siltstone, mudstone, carbonaceous shale, coal, and minor volcanic ash. Tertiary (Miocene) Seldovia Sedimentary Tkb 600 81 Tt SV002Tyonek Formation Conglomerate and subordinate sandstone, siltstone, and coal Tertiary (Miocene and Oligocene) Seldovia Sedimentary Tty 630 630 Tkth KN002Tyonek Formation and Hemlock Conglomerate (undivided) Sandstone, conglomerate, and siltstone Tertiary (Miocene and Oligocene) Kenai Sedimentary Ttyh 850 111 Tclu IL002Copper Lake Formation -- Upper conglomerate member Red-weathering pebble-cobble conglomerate consisting mainly of volcanic rock clasts and containing minor tuff. Unit may be agglomerate rather than conglomerate; ranges from 50 to 100 percent fresh-appearing volcanic rock. Quartzite, schist, greenstone,Tertiary (Eocene and Paleocene?) Sandy interbeds in lower part of unit contain leaves referred to Acer disputabilis Hollick of Eocene (prabable early Eocene) age Iliamna Sedimentary Tcl 850 112 Tcls IL002Copper Lake Formation -- Sandstone and siltstone member Sandy facies is chiefly fine- to medium-grained medium- to greenish-gray, lithic graywacke containing locally abundant tuffaceous and carbonaceous material. Fragments include abundant quartz, schist, volcanic, and granitic rock fragments. Interbedded sTertiary (Eocene and Paleocene?) Iliamna Sedimentary Tcl 850 113 Tcll IL002Copper Lake Formation -- Lower conglomerate member Red-weathering pebble-cobble conglmerate consisting mainly of volcanic rock clasts and containing minor tuff. Volcanic clasts constitute about 25 percent and appear to be derived for the Talkeetna Formation and not fresher-appearing Tertiary volcanic unTertiary (Eocene and Paleocene?) Iliamna Sedimentary Tcl 855 Q 820 Twf? KN002West Foreland Formation Conglomerate, sandstone, and siltstone; mostly tuffaceous, inferred from air photos, covered by thin glacial deposits Tertiary (Eocene and Paleocene?) Kenai Sedimentary Twf 855 855 Twf KN002West Foreland Formation Conglomerate, sandstone, and siltstone; mostly tuffaceous Tertiary (Eocene and Paleocene?) Kenai Sedimentary Twf 855 621 bT KN006Tertiary bedrock Kenai Group and West Foreland Formation; nonmarine sandstone, siltstone, shale, and claystone and local coal Tertiary Kenai Sedimentary Tk 855 Q 634 bT? KN006Tertiary bedrock Kenai Group and West Foreland Formation; nonmarine sandstone, siltstone, shale, and claystone and local coal Tertiary Kenai Sedimentary Tk 855 79 Twf SV002West Foreland Formation Poorly sorted polymictic conglomerate, graywacke, and siltstone; having interbedded tuff and local subaerial basalt flows. Tertiary (Eocene) Seldovia Sedimentary Twf 855 513 Tk SV004Kenai Formation Tan to light-yellow-brown conglomerate, sandstone, and laminated siltstone; few thin coal beds Tertiary, Miocene and Oligocene? Seldovia Sedimentary Twf 1000 400 Tv DI002Volcanic(?) rocks Volcanic rocks based on photo correlation with areas of known volcanic rocks. Tertiary? Dillingham Igneous Tvu 1000 5400 Tv DI005Volcanic(?) rocks Volcanic rocks based on photo correlation with areas of known volcanic rocks. Tertiary? Dillingham Igneous Tvu 1000 512 Tf IL007Lava flows Andesitic to basaltic lavas and associated pyroclastic rocks. Tertiary, middle to late? Iliamna Igneous Tvu 1000 512 Tf KN005Lava flows Andesitic to basaltic lavas and associated pyroclastic rocks. Tertiary, middle to late? Kenai Igneous Tvu 1000ALT 2002 Tda TA020Altered diabase(?) Includes slightly altered to completely altered diabase and biotite basalt Tertiary? Taylor MountainsIgneous 1001 1131 Tv LC002Volcanic rocks Rhyolitic breccia, ash-flow tuff, flows, and intrusive rocks and subordinate mafic and intermediate flows. Unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Formation Tertiary K-Ar ages of 56.2 to 62.7 Ma, however unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Formation. Lake Clark Igneous Trs 1003 115 Tvf LC002Mafic to intermediate flows Mafic to intermediate flows of unit Tv where they constitute separate mappable entities. Unit split into flows likely to be part of the Meshik Arc and assigned an NSACLASS of 1082 and the less certain age unit which are assigned NSACLASS of 1003 Tertiary Lake Clark Igneous Ta 1003 5004 Tvf LC005Mafic to intermediate flows Mafic to intermediate flows of unit Tv where they constitute separate mappable entities.Unit split into flows likely to be part of the Meshik Arc and assigned an NSACLASS of 1082 and the less certain age unit which are assigned NSACLASS of 1003 Tertiary Lake Clark Igneous Ta 1011 0 Td SV002Intermediate, felsic and mafic dikes Dikes of dacite, rhyolite, andesite, and rare basalt; stored in coverage as arcs, arc-code = 50, arc-para1 = 0 early Tertiary Ar-AR isochron(?) age on andesite(?) of 57.0 Ma Seldovia Igneous Thf 1011 200 Tf TA003Felsic porphyry Felsic porphyry Tertiary Taylor MountainsIgneous Tdi 1011 9200 P TA019Felsic porphyry Felsic porphyry Tertiary Taylor MountainsIgneous Tdi 1012 1012 none IL002Volcanic necks, sills, and dikes Spires of basalt and diabase representing the solidified core or vent of Tertiary volcanoes. (NOTE, this is not a map unit. but is shown using a special symbol on the map) Tertiary Iliamna Igneous Thm 1025 170 Tib IL002Intricate Basalt Glassy to porphyritic black to dark-green olivine-augite basalt, largely in the vicinity of Intricate Bay, but also occurs south of Gibraltar Lake Tertiary (Pliocene) Iliamna Igneous Tib 1025 192 Tw TA002Basalt Basalt and locally diabasic intrusive rocks late Tertiary K-Ar ages of 4.62 and 4.72 Ma Taylor MountainsIgneous 1025 192 QTb TA003Basalt Basalt and locally diabasic intrusive rocks late Tertiary K-Ar ages of 4.62 and 4.72 Ma Taylor MountainsIgneous 1025 1202 v TA012Extrusive igneous rocks Olivine basalt flows Tertiary Taylor MountainsIgneous 1025 5025 Tb TA015Extrusive igneous rocks Olivine basalt flows late Tertiary Taylor MountainsIgneous 1025 9025 Tb TA019Extrusive igneous rocks Olivine basalt flows late Tertiary Taylor MountainsIgneous 1030 141 Tglu IL002Gibraltar Lake Tuff -- Upper member Light-gray to white crystal ash-flow tuff. Maximum thickness of 152 to 182 m Tertiary (Pliocene?) Iliamna Igneous Tpgu 1031 142 Tgll IL002Gibraltar Lake Tuff -- Lower member Light- to medium-gray and tan rhyolitic crystal and lithic welded tuff and local interbedded porphyritic rhyolite flows Tertiary (Pliocene? to Oligocene?) Iliamna Igneous Tpgl 1070 5070 Tvt DI005Volcanic rocks, undivided, tuff Gray and purple bedded lithic, crystal, and vitric tuff; light-gray to purple welded crystal and lithic tuff most common. Sample collected along Alagnak River by Janet Curran, USGS-WRD Tertiary (Oligocene and older?) 40Ar/39Ar age on plagioclase of 41.6 Ma Dillingham Igneous Tvr 1070 5615 Tft DI005Felsic volcanic rocks, tuff(?) Cream to light-gray to green layered volcanic rocks. Layering suggests rocks are tuffaceous. early Tertiary Dillingham Igneous Tvr 1070 116 Tvt IL002Volcanic rocks, undivided, tuff Gray, green, and purple bedded lithic, crystal, and vitric tuff; light-gray to tan welded crystal and lithic tuff most common. Tertiary (Oligocene and older?) Iliamna Igneous Tvr 1070 51070Tvt LC005Volcanic rocks Rhyolitic breccia, ash-flow tuff, and flows. Cream, light-gray, green, and purple bedded lithic, crystal, and vitric tuff; light-gray to tan welded crystal and lithic tuff most common Tertiary K-Ar ages of 41.6 ro 45.1 Ma, in adjacent quadrangles Lake Clark Igneous 1081 5081 Tvba DI005Volcanic rocks, undivided, basalt and andesite Dark-gray to green glassy to porphyritic basaltic andesite and andesite lava flows. Locally, basalt, dacite, and rhyolite are common. Many of the rocks are associated with eruptive centers. Unit inferred from adjacent Iliamna quadrangle geologic map. Tertiary (Oligocene and older?) Dillingham Igneous Tm 1081 114 Tv IL002Volcanic rocks, undivided Includes basalt, andesite, tuff, volcanic rubble, and breccia Tertiary (Oligocene and older?) Iliamna Igneous Tvu 1081 113 Tv LC002Volcanic rocks Rhyolitic breccia, ash-flow tuff, flows, and intrusive rocks and subordinate mafic and intermediate flows. Unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Formation Tertiary K-Ar ages of 56.2 to 62.7 Ma, however unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Formation. Lake Clark Igneous Trs 1081 5000 Tv LC005Volcanic rocks Undifferentiated volcanic mafic and felsic flows, tuff flow breccias. Interpreted from air photos Tertiary Lake Clark Igneous Tvu 1081 5001 Tv LC005Volcanic rocks Rhyolitic breccia, ash-flow tuff, flows, and intrusive rocks and subordinate mafic and intermediate flows. Unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Fm. Interpreted from airphotos Tertiary K-Ar ages of 56.2 to 62.7 Ma, however unit is thought to encompass entire Tertiary and may include Jurassic rocks of the Talkeetna Fm. Lake Clark Igneous Trs 1081 5011 Tf TA015Felsic porphyry Felsic porphyry Tertiary Taylor MountainsIgneous Tdi 1082 115 Tvba IL002Volcanic rocks, undivided, basalt and andesite Dark-gray to green glassy to porphyritic basaltic andesite and andesite lava flows. Locally, basalt, dacite, and rhyolite are common. Many of the rocks are associated with eruptive centers. Tertiary (Oligocene and older?) Iliamna Igneous Tm 1082 114 Tvf LC002Mafic to intermediate flows Mafic to intermediate flows of unit Tv where they constitute separate mappable entities. Unit split into flows likely to be part of the Meshik Arc and assigned an NSACLASS of 1082 and the less certain age unit which are assigned NSACLASS of 1003 Tertiary Lake Clark Igneous Ta 1082 5003 Tvf LC005Mafic to intermediate flows Mafic to intermediate flows of unit Tv where they constitute separate mappable entities. Unit split into flows likely to be part of the Meshik Arc and assigned an NSACLASS of 1082 and the less certain age unit which are assigned NSACLASS of 1003. InferTertiary Lake Clark Igneous Ta 1084 5403 Ta DI005Andesite plug Small andesite plug intruding hornfelsed siltstone. Contact metamorphism is not associated with andesite plug. Also includes isolated andesite plug in southeast corner of D-1 quadrangle. Tertiary? Dillingham Igneous Ta 1087 117 Tvr IL002Volcanic rocks, undivided, volcanic rubble and breccia Volcanic rubble and breccia, including some agglomerate; may include deposits of lahars. Tertiary (Oligocene and older?) Iliamna Igneous Tm 1111 5404 Tbb DI005Olivine basalt Massive columnar jointed olivine basalt flows in the area east of the Stuyahok Hills; part of bimodal volcanic suite. The sequence consists of interlayered basalt flows and felsic tuff. Flows range from 3 to 10 m thick. SiO2 content is approximately 48Tertiary? Ar-Ar age of 44 Ma Dillingham Igneous Tbep 1112 5401 Tbr DI005Bimodal volcanic suite, rhyolitic and dacitic tuff Distinctive light colored horizons of felsic tuff interlayered with olivine basalt in the Stuyahok Hills. Tuff composed largely of altered glass and very fresh phenocrysts of plagioclase. Tuff layers approximately 10 to 30 m thick. Age is approximatelTertiary (Eocene) Ar-Ar age of 44 Ma Dillingham Igneous Trs 1125 5405 Tbo DI005Olivine basalt Massive columnar jointed olivine basalt flows in the southwestern D-1 quadrangle (T.4 S., R.41 W.); overlies alaskite (unit TKga) and graywacke of probable Jurassic age (unit Jkw). Newly determined Ar-Ar isochron age is 53.70 +/- 0.62 Ma. SiO2 content Tertiary (early Eocene) Ar-Ar age of 53.70 +/- 0.62 Ma Dillingham Igneous Tbep 1130 6002 Tvi DI005Ignimbrite Crystal tuff containing variable amounts of biotite and feldspar crystals in a tuffaceous matrix. Unit is widespread in the Stuyahok Hills and varies in appearance from crystal tuff to porphyritic plutonic rock. However in all cases, the groundmass is Tertiary (Paleocene) Wallace and others (1989, DI006) report K-Ar age of 57.9 Ho, and 58.6 Bi; new Ar-Ar ages tightly cluster at 59 Ma Dillingham Igneous Tvig 1200 1200 Ti KN002Intrusive rocks Dikes, sills, and stock-lke masses of felsic to mafic composition Tertiary Kenai Igneous Tiu 1200 620 Tg LC006Granitic rocks Granitic rocks Tertiary Lake Clark Igneous Tiu 1203 133 Ti13 LC002Tertiary intrusive rocks -- Unit 13 Granite Multiphase, hypabyssal leucocratic grayish-pink biotite granite Tertiary Lake Clark Igneous Thf 1203 138 Ti18 LC002Tertiary intrusive rocks -- Unit 18 Granite Small area of fractured biotite granite containing as much as 40 percent potassium-feldspar. Tertiary Lake Clark Igneous Togr 1203 139 Ti19 LC002Tertiary intrusive rocks -- Unit 19 Aplite Light-gray, fine-grained xenomorphic granular aplite stock. Younger than Ti -- unit 17. Tertiary Lake Clark Igneous Togr 1205 151 Ti IL002Intrusive rocks Fine- to medium-grained granodiorite and quartz diorite, includes volcanic necks, sills, and dikes. Tertiary Iliamna Igneous Tgd 1275 150 Tqd IL002Quartz Diorite Coarse-grained, light-gray hornblende-biotite quartz diorite. Tertiary (Oligocene) 36 Ma Iliamna Igneous Toqd 1275 126 Ti6 LC002Tertiary intrusive rocks -- Unit 6 Quartz monzodiorite Small irregular body of quartz monzodiorite cutting metamorphic rocks and containing abundant mafic inclusions. Tertiary Lake Clark Igneous Toem 1275ALT 134 Ti14 LC002Tertiary intrusive rocks -- Unit 14 Quartz monzodiorite Heterogeneous, intensely sheared and locally altered medium- to fine-grained rocks ranging from tonalite to monzodiorite. Intruded by Ti unit 13 and intrudes Mesozoic metavolcanic rocks. Tertiary Lake Clark Igneous Taqd 1275 135 Ti15 LC002Tertiary intrusive rocks -- Unit 15 Tonalite Compositionally variable medium-grained, slightly foliated tonalite and quartz diorite Tertiary K-Ar ages between 31 to 35 Ma Lake Clark Igneous Tqd 1275 136 Ti16 LC002Tertiary intrusive rocks -- Unit 16 Granodiorite Medium-gray, medium-grained hypidiomorphic-granular biotite-hornblende granodiorite. According to Reed and Lanphere, is part of Merrill Pass sequenceBiotite granite and biotite-hornblende granite and granodiorite. Possibly two population, uniformly graTertiary K-Ar ages between 31 to 35 Ma Lake Clark Igneous Toem 1300 124 Ti4 LC002Tertiary intrusive rocks -- Unit 4 Granodiorite Medium- to coarse-grained biotite-hornblende granodiorite. Tertiary Lake Clark Igneous Tegr 1300 132 Ti12 LC002Tertiary intrusive rocks -- Unit 12 Granite and granodiorite North of Currant Creek, consist of grayish-white coarse-grained biotite granite; south of Currant Creek consist of medium- to coarse-grained granodiorite. Tertiary Lake Clark Igneous Tegr 1300 137 Ti17 LC002Tertiary intrusive rocks -- Unit 17 Granite Biotite granite and biotite-hornblende granite and granodiorite. Possibly two populations, uniformly grayish-white, coarse-grained biotite granite containing light-pink perthite phenocrysts north of Township 9 N. In T. 9 N and southward, rocks are lessTertiary K-Ar ages between 35 and 41 Ma Lake Clark Igneous Tegr 1300 5300 Ti17 LC005Tertiary intrusive rocks -- Unit 17 Granite Biotite granite and biotite-hornblende granite and granodiorite. Possibly two populations, uniformly grayish-white, coarse-grained biotite granite containing light-pink perthite phenocrysts north of Township 9 N. In T. 9 N and southward, rocks are lessTertiary K-Ar ages between 35 and 41 Ma Lake Clark Igneous 2750Tegr 1300 113 Tg SV002Granodiorite Medium- and coarse-grained biotite granodiorite Tertiary (Eocene) U-Pb monazite age of 56.0, Ar-Ar biotite ages of 54.2, 53.2, 53.4,53.7, and 54.0 Seldovia Igneous Tegr 1318 125 Ti5 LC002Tertiary intrusive rocks -- Unit 5 Gabbronorite Small, coarse-grained stock of hornblende and biotite-bearing olivine gabbronorite cutting Mesozoic sedimentary rocks. Tertiary Lake Clark Igneous Tgl 1320 630 Ti10 IL006Tertiary intrusive rocks -- Unit 10 Granite Medium-grained composite pluton of granite and granodiorite which forms western border of Alaska-Aleutian Range batholith from Little Lake Clark southwestward into the Ilianma quadrangle. Tertiary Iliamna Igneous Tpgr 1320 127 Ti7 LC002Tertiary intrusive rocks -- Unit 7 Granite Coarse- to medium-grained granite. Tertiary Lake Clark Igneous Thgd 1320 130 Ti10 LC002Tertiary intrusive rocks -- Unit 10 Granite Medium-grained composite pluton of granite and granodiorite which forms western border of Alaska-Aleutian Range batholith from Little Lake Clark southwestward into the Ilianma quadrangle. Tertiary Lake Clark Igneous Tpgr 1320 131 Ti11 LC002Tertiary intrusive rocks -- Unit 11 Granodiorite Medium-grained composite body largely of granodiorite but including granite and quartz monzodiorite. Locally includes rocks of Ti10. Tertiary Lake Clark Igneous Tegr 1325 123 Ti3 LC002Tertiary intrusive rocks -- Unit 3 Peralkaline granite Mostly medium-grained hypidiomorphic granular granite containing subhedral to euhedral perthite. Only peralkaline granite associated with Alaska-Aleutian Range bathoilth and probably not related to calc-alkaline rocks of the batholith. Tertiary Lake Clark Igneous Togr 1350 629 Ti9 IL006Tertiary intrusive rocks -- Unit 9 Granodiorite Medium-grained, equigranular hornblende-biotite granodiorite. Intrudes Jurassic unit 2. Tertiary Iliamna Igneous Thgd 1350 121 Ti1 LC002Tertiary intrusive rocks -- Unit 1 Granodiorite Compositionally variable, medium-grained hypidiomorphic granular igneous rock, which depending on perthite content ranges from granodiorite to tonalite. Tertiary Concordant K-Ar age of 61 Ma Lake Clark Igneous Thgd 1350 122 Ti2 LC002Tertiary intrusive rocks -- Unit 2 Quartz monzodiorite Medium- to fine-grained hypidiomorphic granular hornblende-biotite quartz monzodiorite. Cut by Ti unit 10. Tertiary Concordant K-Ar age of 61 Ma Lake Clark Igneous Thgd 1350 128 Ti8 LC002Tertiary intrusive rocks -- Unit 8 Granodiorite Largely medium-grained, equigranular hornblende-biotite silicic granodiorite but ranges from granite to quartz monzodiorite. Intrudes Jurassic and Cretaceous rocks of Alaska-Aleutian Range batholith. Tertiary Lake Clark Igneous Thgd 1350 129 Ti9 LC002Tertiary intrusive rocks -- Unit 9 Granodiorite Medium-grained, equigranular hornblende-biotite granodiorite. Intrudes Jurassic unit 2. Tertiary Lake Clark Igneous Thgd 1600 623 TKv LC006Volcanic rocks Volcanic rocks Tertiary and (or) Cretaceous Lake Clark Igneous TKv 1600Q 624 TKv? LC006Volcanic rocks Volcanic rocks Tertiary and (or) Cretaceous Lake Clark Igneous TKv 1600 1205 TKp LC012Tuff, tuff breccia, and breccia Compositionally undetermined tuff, tuff breccia, and breccia Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1602 5011 Ti DI005Felsic hypabyssal rocks The larger of scattered occurrences of felsic hypabyssal rocks. Occurs as dikes and small plugs. Tertiary? Dillingham Igneous Thf 1602 147 TKi7 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 7 Rhyolite dikes Rhyolite dikes containing phenocrysts of sanidine and high temperature quartz. Tertiary and (or) Cretaceous Lake Clark Igneous TKgp 1602 1914 TKr TA019Hypabyssal intrusive igneous rocks Dikes, sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1603 5603 TKr LC005Rhyolite flows and tuff Rhyolite flows and tuff, includes some dikes. Inferred on basis of Eakins and others (1978). Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1603 1201 TKr LC012Rhyolite flows and tuff Rhyolite flows and tuff, includes some dikes Tertiary or Cretaceous Lake Clark Igneous 1603ALT-SER1202 TKr LC012Rhyolite flows and tuff Rhyolite flows and tuff, includes some dikes Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1604 5603 TKd LC005Dacite flows and pyroclastic rocks Dacite flows and pyroclastic rocks, includes some hypabyssal intrusions. Added from air-photos Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1604 1203 TKd LC012Dacite flows and pyroclastic rocks Dacite flows and pyroclastic rocks, includes some hypabyssal intrusions Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1635 5635 TKb LC005Basalt flows Basalt flows. Added from air-photos Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1635 1204 TKb LC012Basalt flows Basalt flows Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1650 1203 TKu KN012Plutonic rocks, undivided Plutonic rocks Tertiary and Cretaceous Kenai Igneous 1650 1103 TKu LC011Plutonic rocks, undivided Plutonic rocks Tertiary and Cretaceous Lake Clark Igneous 1655 165 TKg DI003Granitic rocks Fine-, medium-, and coarse-grained, light- to dark-gray, rarely pink, plutonic granitic rocks. Chiefly quartz monzonite, granodiorite, and quartz diorite. Tertiary and Cretaceous K/Ar age range of 62.5 to 72.5 m.y. from biotite and hornblende Dillingham Igneous TKg 1655 5165 TKg DI005Granitic rocks Fine-, medium-, and coarse-grained, light- to dark-gray, rarely pink plutonic granitic rocks. Chiefly quartz monzonite, granodiorite, and quartz diorite. In general, alkali content of these rocks is high relative to normal for their SiO2 content (LeMaiTertiary and Cretaceous K-Ar and 40Ar-39Ar ages range from 61 to 67 Ma from biotite and hornblende Dillingham Igneous TKg 1655HFS 5170 TKgm DI009Granitic rocks and mixed hornfels and dikes Fine-, medium-, and coarse-grained, light- to dark-gray, plutonic granitic rocks mixed with felsic dikes and contact metamorphosed volcanic or sedimentary rocks. Outcrop area is south of the Northern pluton, at much lower elevation, suggesting that it mTertiary and Cretaceous 65.26 +/- 0.06 Ma on biotite Dillingham Igneous TKg 1655 5655 TKg LC005Granitic rocks of Tertiary and (or) Cretaceous age Granitic rocks Tertiary and (or) Cretaceous Lake Clark Igneous TKg 1655 621 TKg LC006Granitic rocks Granitic rocks Tertiary and (or) Cretaceous Lake Clark Igneous TKg 1655 622 TKg? LC006Granitic rocks Granitic rocks Tertiary and (or) Cretaceous Lake Clark Igneous TKg 1655 165 TKg TA006Granitic rocks Fine-, medium-, and coarse-grained, light- to dark-gray, rarely pink plutonic granitic rocks. Chiefly quartz monzonite, granodiorite, and quartz diorite. Tertiary and Cretaceous K/Ar age range of 62.5 to 72.5 m.y. from biotite and hornblende Taylor MountainsIgneous TKg 1655 5055 TKg TA015Granitic rocks Granitic rocks. Tertiary or Cretaceous Taylor MountainsIgneous TKg 1655 1912 TKg TA019Intrusive igneous rocks Primarily granite but ranges in composition from diorite to granite. Dikes sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1656 5176 TKg DI005Granitic rocks, Kemuk pluton Coarse-grained pyroxene alkali-feldspare granite. Consists primarily of perthitic feldspar grains surrounded by a fine-grained matric of quartz and feldspar. Contains biotite, pyroxene, and amphibole. Tertiary or Cretaceous 40Ar-39Ar age of 64.45+/- 0.11 Dillingham Igneous TKg 1656 5178 TKg DI005Granitic rocks The Akuluktuk and Tikchik Lake plutons of Wilson and others, 1977. Medium- to Coarse-grained granite, biotite dominant but containing minor amphibole or clinopyroxene. Tertiary and Cretaceous K-Ar and 40Ar-39Ar ages range from 69.7 to 63.4 Ma on biotite and hornblende Dillingham Igneous TKg 1656 5166 TKgs DI009Granitic rocks of the eastern Stuyahok Hills Largely medium- to coarse-grained, light-gray to pinkish biotite monzogranite. Large pluton widely exposed in the eastern part of the Stuyahok Hills. Typically contains large (2cm) phenocrysts of potassium feldspar (orthoclase). Biotite is dominant maTertiary and Cretaceous K-Ar ages reported by Wallace and others (1989) are 61.2 +/- 1.8 Ma (biotite) and 54.5 +/- 1.6 Ma (hornblende, minimum age). Ten newly determined 40Ar-39Ar ages on biotite are tightly grouped between 60.90 +/- 0.04 and 61.70 +/- 0.06 Ma and an 40Ar-39ArDillingham Igneous TKg 1656 5168 TKga DI009Alaskite Coarse- to fine-grained white to off-white alaskite (alkali-feldspar granite) consisting of white feldspar and smoky quartz. Mafic minerals and mica exceedingly sparse in this large (7 km in diameter) body on the southwestern edge of the D-1 quadrangle.Tertiary? An Ar-Ar age determination on biotite yielded 66.64 +/- 0.08 Ma whereas a plateau age of potassium feldspar was 58.2 +/- 0.2 Ma, slightly older that the overlying olivine basalt (unit Tbo, 53.7 Ma) suggesting extended cooling or resetting associated withDillingham Igneous TKg 1656 150 TKi10 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 10 Granite prophyry Hypidiomorphic-granular granite prophyry having quartz, plagioclase and potassium feldspar phenocrysts to 4 mm in a groundmass of 1 mm plagioclase. Very little biotite, local muscovite and zircon. Tertiary and (or) Cretaceous Lake Clark Igneous TKg 1656 151 TKi11 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 11 Granite Medium-grained, xenomorphic granite, subequal biotite and hornblende. Tertiary and (or) Cretaceous Lake Clark Igneous TKg 1656 190 Tg TA002Granitic rocks Granite of Taylor Mountain batholith Tertiary? Taylor MountainsIgneous TKg 1656 3190 TKg TA003Granitic rocks Granite, porphyritic granite, and dikes and sills of rhyolite. Tertiary? Taylor MountainsIgneous TKg 1656 190 Tg TA005Granitic rocks Granite, porphyritic granite, and dikes and sills of rhyolite. Tertiary? Taylor MountainsIgneous TKg 1656 902 i TA009Intrusive igneous rocks Primarily quartz monzonite stock but ranges in composition from grandiorite to granite. Dikes sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1656 14190TKg TA014Granitic rocks Granitic rocks. Tertiary or Cretaceous Taylor MountainsIgneous TKg 1656 5056 TKg TA015Granitic rocks Granite Tertiary or Cretaceous Taylor MountainsIgneous TKg 1657 450 Tg DI002Granitic rocks Coarse- to fine-grained grantic rocks consisiting in part of quartz monzonite and syenite. Tertiary? Dillingham Igneous TKg 1657 5177 TKg DI005Granitic rocks, Kulik Lake pluton Medium-grained pyroxene monzonite. Contains biotite and pyroxene Tertiary or Cretaceous Dillingham Igneous TKg 1657 5172 TKgn DI009Northern pluton Medium-grained biotite monzogranite to syenogranite found in the mountains immediately south of the Koktuli River. Biotite is the only mafic mineral and orthoclase has moderate development of string perthite. SiO2 of analyzed samples has a narrow rangeTertiary or Cretaceous Ar-Ar ages range between 65.50 +/- 0.05 and 66.24 +/- 0.08 Ma on biotite. Dillingham Igneous TKg 1657 5057 TKg TA015Granitic rocks Syenitic rocks Tertiary or Cretaceous Taylor MountainsIgneous TKg 1658 5165 TKg DI005Quartz monzodiorite of the Muklung Hills Quartz monzodiorite but also includes granite in this large multi-phase pluton. Large zoned, twinned and untwin feldspar phenocrysts in a fine-grained matrix of quartz, feldspar, biotite, and hornblende. Tertiary and Cretaceous 40Ar-39Ar ages range from 65.81 to 67.94 Ma from biotite Dillingham Igneous TKg 1658 5167 TKpsw DI009Pike Creek plutons, southwestern unit Medium- to coarse-grained, light-gray biotite monzogranite or quartz monzodiorite. Equigranular and contains more pyroxene than unit TKpnw above. Clinopyroxene, some of which containing pinkish orthopyroxene cores is common in some samples, whereas othTertiary and Cretaceous Ar-Ar biotite ages are 61.11 +/- 0.07 and 61.67 +/- 0.05 Ma Dillingham Igneous TKg 1658 5169 TKpe DI009Pike Creek plutons, eastern unit Medium-grained, light-gray biotite monzogranite to quartz monzonite. Hornblende to biotite ratio approximately 6:4; may contain orthoclase phenocrysts and hornblende may have relict clinopyroxene cores. Major element chemical analysis indicates 63.2 peTertiary and Cretaceous Ar-Ar age of 63.09 +/- 0.05 Ma on biotite Dillingham Igneous TKg 1658 5171 TKgnw DI009Northwest pluton Porphyritic amphibole-bearing monzonite. Outcrops on isolated low-relief ridge south of the Koktuli River and west of the Northern pluton. Consists of plagioclase, amphibole (kaersutite?) , and clinopyroxene phenocrysts in a fine-grained groundmass. STertiary or Cretaceous Ar-Ar plateau age was 63.76 +/- 0.27 Ma on amphibole Dillingham Igneous TKg 1658 5173 TKpnw DI009Pike Creek plutons, northwestern unit Medium-grained, light-gray hornblende-biotite monzogranite to quartz monzodiorite. May contain large phenocrysts of orthoclase; biotite to hornblende ratio approximately 2:1. Two major element chemical analyses have 67.8 and 68.2 percent SiO2. Tertiary and Cretaceous Ar-Ar biotite ages are 65.72 +/- 0.04 and 66.49 +/- 0.07 Ma Dillingham Igneous TKg 1658 5174 TKge DI009Eastern granitic rocks-Hornblende quartz monzonite Hornblende quartz monzonite. Texturally similar to the granitic rocks of the eastern Stuyahok Hills in having large (2 cm) feldspar phenocrysts, however hornblende is the more common mafic mineral in these rocks. An 40Ar-39Ar age of 61.3 +/- 0.2 Ma on Tertiary and or Cretaceous 40Ar-39Ar age of 61.3 +/- 0.2 Ma on hornblende Dillingham Igneous 1658 145 TKi5 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 5 Quartz monzonite Numerous small intrusive bodies of quartz monzonite in the central part of the quadrangle indentified by Eakins and others (1978) Tertiary and (or) Cretaceous K-Ar age of 71.3 Ma on one body located in T.5N, R.30W. Lake Clark Igneous TKg 1658 1206 TKqm LC012Quartz monzonite Quartz monzonite and minor granodiorite Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1658 191 Tqm TA002Quartz monzonite Quartz monzonite. Tertiary or Cretaceous K-Ar age of 67.1 Ma on amphibole Taylor MountainsIgneous TKg 1658 1002 i TA010Intrusive igneous rocks Primarily quartz monzonite stock but ranges in composition from granodiorite to granite. Dikes sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1658 1102 i TA011Intrusive igneous rocks Primarily quartz monzonite stock but ranges in composition from grandiorite to granite. Dikes sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1658 1203 i TA012Intrusive igneous rocks Primarily quartz monzonite stock but ranges in composition from grandiorite to granite. Dikes sills, and small plugs are primarily porphyritic rhyolite. Tertiary Taylor MountainsIgneous TKg 1660 152 TKi IL002Intrusive rocks Chiefly medium- to coarse-grained, light-gray granodiorite, quartz monzonite, and quartz diorite plutons. Tertiary or Cretaceous Iliamna Igneous TKgd 1660 653 TKi13 IL006Tertiary and (or) Cretaceous intrusive rocks -- Unit 13 Granodioritic rocks Light-colored intrusive rocks, presumed granodiorite. Tertiary and (or) Cretaceous Iliamna Igneous TKgd 1660 2905 TKgd KN002Granodiorite, quartz diorite, and diorite Tertiary or Late Cretaceous Kenai Igneous TKm 1660 142 TKi2 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 2 Granodiorite Medium- to locally fine-grained hypidiomorphic-granular, pinkish-gray granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 144 TKi4 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 4 Granodiorite Medium- to fine-grained, light-pinkish-gray hornblende-biotite granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 149 TKi9 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 9 Granodiorite Coarse- to fine-grained, hypidiomorphic-seriate textured granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 152 TKi12 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 12 Granodioritic rocks Light-colored intrusive rocks, presumed granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 153 TKi13 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 13 Granodioritic rocks Light-colored intrusive rocks, presumed granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 154 TKi14 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 14 Granodiorite Medium-grained, hypidiomorphic granular, seriate granodiorite Biotite more abundant that hornblende. Tertiary and (or) Cretaceous K-Ar age of 64 Ma Lake Clark Igneous TKgd 1660Q 5660 TKi9 LC005Tertiary and (or) Cretaceous intrusive rocks -- Unit 9 Granodiorite Coarse- to fine-grained, hypidiomorphic-seriate textured granodiorite.. added from airphotos Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 5661 TKi12 LC005Tertiary and (or) Cretaceous intrusive rocks -- Unit 12 Granodioritic rocks Light-colored intrusive rocks, presumed granodiorite. Added from air photos Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1660 192 Tg TA002Granitic rocks Granodiorite or tonalite based on analysis and thin-sections (54AHr 10) Tertiary? Taylor MountainsIgneous TKg 1660 5060 TKgd TA015Granitic rocks Granodiorite or tonalite Tertiary? Taylor MountainsIgneous TKg 1665HFS 5665 TKpd DI009Dioritic rocks Monzodioritic rocks of Pike Creek-Largely medium-grained quartz monzodioritic and dioritic rocks in the southeast D-1 quadrangle. SiO2 content ranges between 57.4 and 61.4 percent; as with other rocks in this region, alkalis tend to be higher that normaTertiary or Cretaceous Ar-Ar age of 64.42 +/- 0.04 Ma on biotite and on hornblende of 61.1 +/- 0.7 Ma which is essentially the same as the surrounding granodiorite. As the surrounding granodiorite shows no evidence of contact metamorphism, this hornblende age should be considDillingham Igneous TKqd 1665 5666 TKqd DI009Monzontic rocks Coarse- to fine-grained monzogranitic to monzodioritic rocks in the southeast D-1 quadrangle. Rocks are typically dark green, have sparse clinopyroxene, and locally show evidence of contact metamorphism. Amphibole dominant mafic, tends to be green pleoTertiary or Cretaceous An Ar-Ar age of 61.3 +/- 0.2 Ma on hornblende is coeval with some parts of the Pike Creek pluton; however, as for the hornblende date on the dioritic rocks of Pike Creek (unit TKpd above), this age may represent a minimum age Dillingham Igneous TKqd 1665 141 TKi1 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 1 Diorite Altered pyroxene gabbro and hornblende-pyroxene diorite. Assigned Tertiary or Cretaceous age, however, Jurassic age can not be ruled out. Tertiary and (or) Cretaceous Lake Clark Igneous TKqd 1665 143 TKi3 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 3 Quartz diorite Predominantly fine- to medium-grained altered hornblende-biotite quartz diorite and less commonly granodiorite. Tertiary and (or) Cretaceous Lake Clark Igneous TKqd 1665 146 TKi6 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 6 Diorite Numerous small diorite intrusions in central part of quadrangle. Tertiary and (or) Cretaceous K-Ar age of 69.4 Ma Lake Clark Igneous TKqd 1665 148 TKi8 LC002Tertiary and (or) Cretaceous intrusive rocks -- Unit 8 Monzodiorite Medium-grained, hypidiomorphic-seriate textured monzodiorite., contains subequal hornblende and clinopyroxene. Tertiary and (or) Cretaceous Lake Clark Igneous TKgd 1665 1207 TKqm LC012Diorite Diorite Tertiary (Paleocene) or Late Cretaceous Lake Clark Igneous 1665 1907 TKd TA019Diorite Diorite reported northeast of Cinnabar Creek Tertiary or Cretaceous Taylor MountainsIgneous TKg 1955 180 Kk IL002Kaguyak Formation Silty, thin-bedded to massive, fine- to medium-grained, green to gray arkosic wacke sandstone and interbedded siltstone. Late Cretaceous (Campanian, Maestrichtian) Ammonits and pelecypods, mainly Diplomoceras notabile Whiteves, Pachydiscus (Neodesmocers) sp., and Inoceramus Iliamna Sedimentary Kkg 1961 72 Kk SV002Kaguyak Formation, nonmarine sedimentary rocks Sandstone, conglomerate, siltstone and interbedded coal Late Cretaceous Sporomorphs: Cranwellia striata Srivastava, Balmeisporites spp., Wodehouseia spinata Staley, Proteacidites spp., Aquilapollenites bertillonites Funjhouser, A. reticulatus Mtchediishvilli, A delicatus Stanley Seldovia Sedimentary Khc 1970Q 5971 Kk DI005Kuskokwim Group? Photogeologic interpretation based on adjoining Taylor Mountains mapping. Unit consists of dark siltstone and sandstone. Cretaceous Dillingham Sedimentary Kk 1970 5970 Kk DI009Kuskokwim Group Well-bedded, rhythmically interbedded dark siltstone and sandstone. Found only north of the Koktuli River Cretaceous Dillingham Sedimentary Kk 1970 191 KJs LC002Sedimentary rocks Interbedded medium-gray, medium- to fine-grained lithic graywacke, silty sandstone, black shale, and local conglomerate. Regional strike is a consistent N50E and parallel to fold axes. Rocks range from unmetamorphosed but highly indurated to local wellCretaceous? and Jurassic Only fossil is Buchia mosquensis(?) of Late Jurassic age. Lake Clark Sedimentary KJf 1970 1970 Kk LC005Kuskokwim Formation, undivided Sandstone and siltstone Cretaceous Lake Clark Sedimentary Kk 1970 5316 KJsh LC005Interbedded marine volcaniclastic sandstone, siltstone, and shale -- siltstone, argillite, and shale Interbedded marine volcaniclastic sandstone, siltstone, and shale -- siltstone, argillite, and shale containing important but subordinate beds of volcaniclastic sandstone. Inferred on basis of Eakins and others (1978). Cretaceous or Late Jurassic? Lake Clark Sedimentary 1970 612 Kk LC006Kuskokwim Formation, undivided Sandstone and siltstone Cretaceous Lake Clark Sedimentary Kk 1970 1209 KJsh LC012Interbedded marine volcaniclastic sandstone, siltstone, and shale -- siltstone, argillite, and shale Interbedded marine volcaniclastic sandstone, siltstone, and shale -- siltstone, argillite, and shale containing important but subordinate beds of volcaniclastic sandstone. Late Jurassic? Possible belemnoid at one locality Lake Clark Sedimentary 1970HFS 1210 KJh LC012Interbedded marine volcaniclastic sandstone, siltstone, and shale -- hornfels Interbedded marine volcaniclastic sandstone, siltstone, and shale -- dark gray, locally gossanized, massive, hornfelsed KJs and KJsh, contains some spotted phyllite and numerous unmappable dikes. Late Jurassic? Possible belemnoid at one locality Lake Clark Sedimentary 1970Q 180 Kk TA002Kuskokwim Group? Sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kk 1970 3180 Kk TA003Kuskokwim Group sedimentary rocks Sandstone, siltstone, shale, and conglomerate (Added, not in source) Cretaceous Taylor MountainsSedimentary Kk 1970 4180 Kk TA004Kuskokwim Group? Sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kk 1970 121 Kk TA006Kuskokwim Group Marine sedimentary sequence consisting of graywacke, sandstone, conglomerate, siltstone, and shale. Cretaceous Early Cretaceous (Albian) age assigned from fossils found north of the map area. Taylor MountainsSedimentary Kk 1970HFS 903 h TA009Hornfels Contact metamorphic zones adjacent to igneous intrusive rocks. Cretaceous Taylor MountainsMetamorphic Kk 1970Q 904 s TA009Sedimentary rocks Interbedded graywacke and shale, with local interbeds of argillite and conglomerate. Cretaceous Taylor MountainsSedimentary Kk 1970HFS 1003 h TA010Hornfels Contact metamorphic zones adjacent to igneous intrusive rocks. Cretaceous Taylor MountainsMetamorphic Kk 1970 1004 s TA010Sedimentary rocks Interbedded graywacke and shale, with local interbeds of argillite and conglomerate. Cretaceous Taylor MountainsSedimentary Kk 1970HFS 1103 h TA011Hornfels Contact metamorphic zones adjacent to igneous intrusive rocks. Cretaceous Taylor MountainsMetamorphic Kk 1970 1104 s TA011Sedimentary rocks Interbedded graywacke and shale, with local interbeds of argillite and conglomerate. Cretaceous Taylor MountainsSedimentary Kk 1970 5180 Kk TA015Kuskokwim Group? Inferred to be Kuskokwim Group consisting of sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kk 1970 1906 Kk TA019Kuskokwim Group Fine- to medium-grained often micaceous gray greywacke or silty greywacke. Occasionally crossbedded, or with siltstone partings. Rare argillite pebbles Cretaceous Taylor MountainsSedimentary 1985 181 Kka TA002Kuskokwim Group, nearshore facies Sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kkn 1985 1985 Kka TA008Kuskokwim Group, nearshore facies Sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kkn 1985 5181 Kka TA015Kuskokwim Group, nearshore facies Sandstone, siltstone, shale, and conglomerate. Inferred from Platt and Muller (TA002) and Hoare and Condon (TA019) Cretaceous Taylor MountainsSedimentary Kkn 1985 19181Kka TA019Kuskokwim Group, nearshore facies Sandstone, siltstone, shale, and conglomerate Cretaceous Taylor MountainsSedimentary Kkn 2190 2190 KJm KN003McHugh Complex Weakly metamorphosed siltstone, graywacke, arkose, and conglomeratic sandstone; greenstone (mostly basaltic), metachert, and argillite Cretaceous and (or) Jurassic Kenai Sedimentary Kmx 2190 74 KPmc SV002McHugh Complex, basalt and chert Pillow and massive basalt, depositionally overlain by radiolarian chert. Early Cretaceous (Albian) to Middle Triassic (Ladinian) Cretaceous to Triassic radiolaria in bedded chert Seldovia Sedimentary Kmx 2190 75 KPms SV002McHugh Complex, graywacke and conglomerate Fault-bounded slices of massive conglomerate and graywacke. Early Cretaceous to Early Jurassic (Pliensbachian) Pliensbachian radiolaria in underlying ribbon chert Seldovia Sedimentary Kmx 2190 77 KPm SV002McHugh Complex, undivided Complexly deformed tectonic assemblage of diverse lithologies (melange). Lithologies include argillite, tuff, graywacke, basalt, chert, outcrop-scale melange, conglomerate, gabbro, and limestone. Rocks typically show prehnite-pumpellyite facies metamorCretaceous to Permian Permian conodonts and fusilinids. Seldovia Tectonite Kmx 2260 210 Tv TA003Volcanogenic sedimentary rocks Volcanogenic sedimentary rocks. Tertiary Taylor MountainsIgneous Tvep 2260Q 1509 Kkv TA015Tuff and related rocks Tuff, some cherty argillite, minor limestone and locally, dikes extrapolation by inferrence from Hoare and Condon notes Cretaceous? Taylor MountainsIgneous 2260 1909 Kkv TA019Tuff and related rocks Tuff, some cherty argillite, minor limestone and locally, dikes Cretaceous? Taylor MountainsIgneous 2401 0 Kd SV002Intermediate dike Basalt-andesite dike intruding McHugh Complex. Stored in coverage as arcs, arc-code = 50 and arc-para1 = 5 Early Cretaceous Ar-Ar hornblende plateau age of 115 Ma Seldovia Igneous Kd 2410 902 Ku KN009Plutonic rocks, undivided Plutonic rocks, undivided Late Cretaceous Kenai Igneous 2410 606 Kg LC006Granitic rocks Granitic rocks Cretaceous Lake Clark Igneous Kg 2420 667 Ki7 IL006Cretaceous intrusive rocks -- Unit 7 Granodiorite Medium-grained, medium-gray hypidiomorphic-granular granodiorite. Hornblende domination mafic, shows varying degrees of alteration. Biotite locally present. Locally cataclasis/mylonization. Cretaceous Iliamna Igneous Kgd 2420 670 Ki10 IL006Cretaceous intrusive rocks -- Unit 10 Granodiorite Medium-grained seriate, whitish-gray granodiorite. Cretaceous Iliamna Igneous Kgd 2420 1 Kgd IL009Grandoirite? Granitic rocks associated with the Pebble Copper deposit Cretaceous Dates between 89 and 100 Ma Iliamna Igneous 2420 161 Ki1 LC002Cretaceous intrusive rocks -- Unit 1 Granodiorite Light- to medium-gray, medium-grained, seriate, hypidiomorphic granular granodiorite. Cretaceous Lake Clark Igneous Kgd 2420 162 Ki2 LC002Cretaceous intrusive rocks -- Unit 2 Quartz monzodiorite Medium- to coarse-grained, locally foliated composite pluton cheifly of hornblende-biotite quartz monzodiorite. Possibly the same pluton as unit Ki3, LC002. Cretaceous Lake Clark Igneous Kgd 2420 163 Ki3 LC002Cretaceous intrusive rocks -- Unit 3 Quartz monzodiorite Medium- to coarse-grained, medium-gray hornblende-biotite quartz monzodiorite. Possibly same pluton as Ki2, LC002. Cretaceous Lake Clark Igneous Kgd 2420 167 Ki7 LC002Cretaceous intrusive rocks -- Unit 7 Granodiorite Medium-grained, medium-gray hypidiomorphic-granular granodiorite. Hornblende domination mafic, shows varying degrees of alteration. Biotite locally present. Locally cataclasis/mylonization. Cretaceous Lake Clark Igneous Kgd 2420 169 Ki9 LC002Cretaceous intrusive rocks -- Unit 9 Granodiorite Ranges from silicic granodiorite to mafic tonalite and quartz diorite. Medium-grained, seriate and many show weak to strong cataclasis (probably mylonitic from description). Some have subvertical, northeast trending primary foliation. Cretaceous Lake Clark Igneous Kgdc 2420 170 Ki10 LC002Cretaceous intrusive rocks -- Unit 10 Granodiorite Medium-grained seriate, whitish-gray granodiorite. Cretaceous Lake Clark Igneous Kgd 2420 171 Ki11 LC002Cretaceous intrusive rocks -- Unit 11 Granodiorite Medium- to coarse-grained subporphyritic granodiorite. Cretaceous Lake Clark Igneous Kgd 2420 173 Ki13 LC002Cretaceous intrusive rocks -- Unit 13 Granodiorite Primarily granodiorite but includes some granite. Notably, is generally coarse-grained. Low color index, biotite primary mafic, with traces of hornblende and muscovite in all examined thin-sections. Cretaceous Lake Clark Igneous Kgd 2420 6420 Ki11 LC005Cretaceous intrusive rocks -- Unit 11 Granodiorite Medium- to coarse-grained subporphyritic granodiorite. Polygons added based on air photo interpretation of scoured bedrock Cretaceous Lake Clark Igneous 2750Kgd 2430 172 Ki12 KN008Cretaceous intrusive rocks -- Unit 12 Quartz diorite Locally foliated, seriate hornblende-biotite quartz diorite. Biotite-hornblende rationis quite variable although color index remains constant. Deuteric epidote common. Extension from adjacent Lake Clark quadrangle Cretaceous Kenai Igneous Kgd 2430 164 Ki4 LC002Cretaceous intrusive rocks -- Unit 4 Quartz diorite Composite igneous mass that includes hornblende-pyroxene gabbro and diorite, quartz diorite, tonalite, and minor granodiorite. Quartz diorite is the most abundant rock type and is medium- to coarse-grained, locally foliated, seriate and has more hornbleCretaceous Lake Clark Igneous Kqd 2430 165 Ki5 LC002Cretaceous intrusive rocks -- Unit 5 Quartz diorite Mafic igneous rocks, chiefly quartz diorite. Medium- to locally coarse-grained and having a well developed primary subvertical foliation that trends northeat. Most samples show cataclasis (mylonization?), which is pronouced near the shear zone in southCretaceous Lake Clark Igneous Kgdc 2430 166 Ki6 LC002Cretaceous intrusive rocks -- Unit 6 Quartz diorite Slightly foliated, medium-grained, seriate, hornblende-biotite quartz diorite. Cretaceous Lake Clark Igneous Kqd 2430 172 Ki12 LC002Cretaceous intrusive rocks -- Unit 12 Quartz diorite Locally foliated, seriate hornblende-biotite quartz diorite. Biotite-hornblende rationis quite variable although color index remains constant. Deuteric epidote common. Cretaceous Lake Clark Igneous Kgd 2460 668 Ki8 IL006Cretaceous intrusive rocks -- Unit 8 Granite Coarse-grained, subporpyritic granite. Part of a granite body exposed to the south in Iliamna quadrangle. Cretaceous Iliamna Igneous Kg 2460 168 Ki8 LC002Cretaceous intrusive rocks -- Unit 8 Granite Coarse-grained, subporpyritic granite. Part of a granite body exposed to the south in Iliamna quadrangle. Cretaceous Lake Clark Igneous Kg 2470 5470 Kgk DI005Potassic granitic rocks of the Okstukuk Hills Okstukuk Hills, biotite granite or syenite having very coarse feldspar laths, medium-grained very fresh biotite and fine-grained clinopyroxene Late Cretaceous Ar-Ar total fusion age 84.49 +/- 0.05 biotite Dillingham Igneous 2470 160 Kqm IL002Quartz monzonite Massive, coarse-grained light-gray porphyritic quartz monzonite. Late Cretaceous K-Ar age on co-existing biotite and hornblende yielded 80.7 and 83.4 Ma and hornblende yielded 74.1 Ma Iliamna Igneous Kg 2470 175 Ki15 LC002Cretaceous intrusive rocks -- Unit 15 Quartz monzonite Fine- to medium-grained hypidiomorphic seriate quartz monzonite. Cretaceous K-Ar age on hornblende is "Late Cretaceous" Lake Clark Igneous Kg 2480 174 Ki14 LC002Cretaceous intrusive rocks -- Unit 14 Granodiorite Porphyritic granodiorite having phenocrysts of quartz, plagioclase, biotite, and glomeroporphyritic clusters of pale-green amphibole in a groundmass of quartz and mostly potassic feldspar. Cretaceous K-Ar age on biotite is "Late Cretaceous" Lake Clark Igneous Kgd 2480 5480 Kg TA015Granodiorite Called granodiorite tentatively based on mode. Chemistry suggests diorite probably -- most similar to diorite field of LeMaitre (1976). More probably proper name might be quartz diorite. Cretaceous 40/39 age of 75.22 Ma Taylor MountainsIgneous 2700 2700 KJv KN003Valdez Group (?) Metawacke, metasiltstone, and argillite; locally phyllitic Cretaceous and Jurassic (?) Kenai Metamorphic Kvs 2700 71 Kv SV002Valdez Group Thick sequences of drab, rythmically alternating multiply deformed turbidites, including metasandstone, metasiltstone, argillite, slate, and phyllite, and rare beds of pebbly argillite and metasandstone; generally beds are a few centimeters to a few metLate Cretaceous Maestrichtian and Campanian(?) Inoceramus Seldovia Metamorphic Kvs 2700 1071 Kvm SV002Melange of Iceworm Peak Tectonic melange consisting of blocks of graywacke in a phacoidally cleaved matrix of slate having a Valdez Group protolith. Late Cretaceous Seldovia Metamorphic Kvs 2830 300 KCg1 DI002Gemuk Group -- clastic rocks Primarily coarse-grained clastic rocks containing some fine-grained cherty and volcanic material. Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Dillingham Sedimentary KJsv 2830 7300 KJvs DI007Togiak-Tikchik Complex mixed clastic rocks Primarily coarse-grained clastic rocks containing some fine-grained cherty and volcanic material. Highly contorted bedding common Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Dillingham Sedimentary 2830 183 KCg1 TA002Gemuk Group -- clastic rocks Primarily coarse-grained clastic rocks containing some fine-grained cherty and volcanic material. Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Taylor MountainsSedimentary KJsv 2830 183 KJs TA003Argillite and graywacke Argillite and graywacke Cretaceous to Jurassic Taylor MountainsSedimentary KJs 2830 183 KJs TA004Argillite and graywacke Argillite and graywacke Cretaceous to Jurassic Taylor MountainsSedimentary KJs 2830 1510 s TA015Sedimentary rocks Interbedded graywacke and shale, with local interbeds of argillite and conglomerate. In this quadrangle (D-8), most certainly includes rocks of the Gemuk Group and to a lesser extent Kuskokwim Group. Includes, based on Hoare and Condon notes of 1969 anCretaceous Taylor MountainsSedimentary 2830 1910 Mzgg TA019Greywacke, greenstone, chert, and limestone Calcareous argillic greywacke, greenstone, chert, cherty argillite, limestone, and greenschist Mesozoic? Taylor MountainsMetamorphic 2831 1531 KJsvi TA015Greywacke, greenstone, chert, and limestone Calcareous argillic greywacke, greenstone, chert, cherty argillite, limestone, and greenschist apparently cut by dike swarms or shallow intrusions. Unit inferred from air-photos Mesozoic? Taylor MountainsMetamorphic 2855 9312 Jk DI009Graywacke and conglomerate Typically dark-green or gray massive sandstone, although coarse-pebble conglomerate is locally present. Rare fragmentary fossils are found within map area; a sample we collected in 2001 yielded fragments of Buchia, suggesting a Late Jurassic or Early CrMiddle to Late Jurassic? Rare fragmentary fossils, appearing to be possibly Buchia. Reported Jurassic fossils found by Unocal in 1959. Dillingham Sedimentary Jkw 2855 181 KJs IL002Sedimentary rocks, undivided Dark-gray to green lithic metagraywacke, polymicitc conglomerate, and argillite are main rock types. All are low-grade metamorphic, ranging from prehnite-pumpellyite to greenschist facies. Argillite and siltstone facies show evidence of turbidite deposJurassic or Cretaceous Nearly identical suite in the Nushagak Bay quadrangle yielded Middle Jurassic fossils, however a Cretaceous age can not be ruled out for the rocks in the Iliamna quadrangle (Graywacke of Kulukak Bay, NSA = 3140). Iliamna Metamorphic Jkw 2855 190 KJs LC002Sedimentary rocks Interbedded medium-gray, medium- to fine-grained lithic graywacke, silty sandstone, black shale, and local conglomerate. Regional strike is a consistent N50E and parallel to fold axes. Rocks range from unmetamorphosed but highly indurated to local wellCretaceous? and Jurassic Only fossil is Buchia mosquensis(?) of Late Jurassic age. Lake Clark Sedimentary KJf 2855 300 KJkr LC003Koksetna River sequence Complexly deformed volcanic-lithic turbidites. Consists of thick monotonous sequence of thin sandstone interbedded with pelagic shale. Coarse, unsorted and chaotic matrix-supported conglomerate occurs sporadically Early Cretaceous (Valanginian) to Late Jurassic (Kimmeridgian)Two fossils reported, late Jurassic (Kimmeridgian) and Early Cretaceous (Valanginian) Lake Clark Sedimentary KJkr 2855 5181 Jkw LC005Sedimentary rocks, undivided Small area shown as KJs by Wallace and the extension of map unit KJs from the Iliamna map to the south. Assigned to unit KJkr. Also includes a single polygon in southwest part of quadrangle that is extension of unit KJs of the Iliamna quadrangle. PresJurassic or Cretaceous Nearly identical suite in the Nushagak Bay quadrangle yielded Middle Jurassic fossils, however a Cretaceous age can not be ruled out for the rocks in the Iliamna quadrangle (Graywacke of Kulukak Bay, NSA = 3140). Lake Clark Metamorphic 2855 5315 KJs LC005Interbedded marine volcaniclastic sandstone, siltstone, and shale -- sandstone Interbedded marine volcaniclastic sandstone, siltstone, and shale -- volcaniclastic sandstone containing important but subordinate beds of siltstone and shale and minor beds of granule conglomerate. Inferred on basis of Eakins and others (1978). Late Jurassic? Lake Clark Sedimentary 2855 608 KJkr LC006Koksetna River sequence Jura-Cretaceous flysch, southern part of Kahiltna terrane Cretaceous and Jurassic Lake Clark Sedimentary KJkr 2855Q 609 KJkr? LC006Koksetna River sequence? Jura-Cretaceous flysch, southern part of Kahiltna terrane Cretaceous and Jurassic Lake Clark Sedimentary KJkr 2855 610 KJs LC006Flysch sequence, undivided Jura-Cretaceous flysch, southern part of Kahiltna terrane Cretaceous and Jurassic Lake Clark Sedimentary KJf 2855HFS 611 KJs LC006Flysch sequence, undivided, hornfels Jura-Cretaceous flysch, southern part of Kahiltna terrane Cretaceous and Jurassic Lake Clark Sedimentary KJf 2855 1208 KJs LC012Interbedded marine volcaniclastic sandstone, siltstone, and shale -- sandstone Interbedded marine volcaniclastic sandstone, siltstone, and shale -- volcaniclastic sandstone containing important but subordinate beds of siltstone and shale and minor beds of granule conglomerate. Late Jurassic? Probable Buchia mosquensis at one locality Lake Clark Sedimentary 2855 5150 KJs TA015Sedimentary rocks Presence inferred on the basis of similar rocks in Dillingham quadrangle to the south and the Lake Clark quadrangle to east. Fossil collections by UNOCAL geologists in 1959, originally reported as being in the Dillingham quadrangle were most likely fromCretaceous? and Jurassic Only fossil is Buchia mosquensis(?) of Late Jurassic age. Taylor MountainsSedimentary KJf 2870HFS 5230 KJv DI009Olivine basalt Olivine basalt flows and fragmental mafic volcanic rocks-Ranges in apparent composition from andesite to basalt based on field calls. Part of unit KJvs volcanic and sedimentary rocks; mapped separately only locally. Cretaceous? Dillingham Igneous KJv 2872 127 KJvs DI003Volcanic and sedimentary rocks Thick marine unit consisting of volcanic and sedimentary rocks. Volcanic rocks range in composition from mafic pillow basalts to more abundant andesitic and trachytic flows, tuff, and breccia. Interbedded with the volcanic rocks are tuffaceous siltstonEarly Cretaceous to Middle Jurassic Radiolaria of Late Jurassic to Early Cretaceous age, and fragmentary ammonites of Jurassic age. Dillingham Sedimentary KJvs 2872 5872 KJvs DI005Volcanic and sedimentary rocks Thick marine unit consisting of volcanic and sedimentary rocks. Volcanics range in composition from mafic pillow basalts to more abundant andesitic and trachytic flows, tuffs, and breccias. Interbedded with the volcanic rocks are tuffaceous siltstone, Early Cretaceous to Middle Jurassic Radiolaria of Late Jurassic to Early Cretaceous age, and fragmentary ammonites of Jurassic age. Dillingham Sedimentary KJvs 2872 9872 KJvs DI009Volcanic and sedimentary rocks Low-grade metamorphic or contact metamorphosed volcanic and lesser sedimentary rocks. Altered volcanic breccia is relatively abundant; however in the southwestern part of T.4 S., R.40 W., unit consists largely of vertically standing beds of contact-metaEarly Cretaceous to Middle Jurassic Radiolaria of Late Jurassic to Early Cretaceous age and fragmentary ammonites of Jurassic age have been collected from this unit in the Goodnews Bay quadrangle to the west (Hoare and Coonrad, 1978) Dillingham Sedimentary KJvs 2900 1350 Tgd KN002Granodioritic rocks Granodiorite and quartz diorite Tertiary Age assigned revised based on Nelson and others (1983) Kenai Igneous Thgd 2900 180 KJi LC002Cretaceous(?) and Jurassic(?) intrusive rocks -- Quartz monzodiorite Medium-gray, medium-grained, hypidiomorphic granular hornblende-biotite quartz monzodiorite containing variable amounts of clinopyroxene. Flow structures locally present and hornblende and plagioclase is aligned in a north-northeast direction. Cretaceous? and Jurassic? K-Ar biotite and hornblende ages ranging from 57.4 to 95.1 Ma Lake Clark Igneous KJg 3000 810 Js IL008Sedimentary rocks Sedimentary rocks, undifferentiated Jurassic Iliamna Sedimentary 3000 11300Js KN011Sedimentary rocks Sedimentary rocks, undifferentiated Jurassic Kenai Sedimentary 3000 601 J LC006Jurassic sedimentary rocks Jurassic sedimentary rocks Jurassic Lake Clark Sedimentary Jsu 3000 5300 Js SV005Sedimentary rocks Sedimentary rocks, undifferentiated Jurassic Seldovia Sedimentary 3010 120 Jn IL002Naknek Formation Arkose, conglomerate, sandstone, siltstone, and shale Late Jurassic (Oxfordian to Tithonian) Ammonites and pelecypods, especially Buchia which provides tight age control Iliamna Sedimentary Jn 3010 3010 Jn KN002Naknek Formation Sandstone, arkose, conglomerate, and siltstone Late Jurassic Kenai Sedimentary Jn 3010 47 Jn SV002Naknek Formation Arkose, conglomerate, sandstone, siltstone, and shale Late Jurassic (Oxfordian to Kimmeridgian) Ammonites and pelecypods, especially Buchia which provides tight age control Seldovia Sedimentary Jn 3012 516 Jnss IL007Naknek Formation, lower sandstone member Thin-bedded to massive arkosic sandstone, graywacke, and siltstone, mainly restricted to central part of region Late Jurassic Iliamna Sedimentary Jnn 3012 516 Jnss KN005Naknek Formation, lower sandstone member Thin-bedded to massive arkosic sandstone, graywacke, and siltstone, mainly restricted to central part of region Late Jurassic Kenai Sedimentary Jnn 3012 516 Jnss SV004Naknek Formation, lower sandstone member Thin-bedded to massive arkosic sandstone, graywacke, and siltstone, mainly restricted to central part of region Late Jurassic Seldovia Sedimentary Jnn 3013 515 Jns IL007Naknek Formation, Snug Harbor Siltstone Member Massive to thin-bedded dark-gray to black siltstone; laminated near base Late Jurassic Iliamna Sedimentary Jns 3013 515 Jns KN005Naknek Formation, Snug Harbor Siltstone Member Massive to thin-bedded dark-gray to black siltstone; laminated near base Late Jurassic Kenai Sedimentary Jns 3013 515 Jns SV004Naknek Formation, Snug Harbor Siltstone Member Massive to thin-bedded dark-gray to black siltstone; laminated near base Late Jurassic Seldovia Sedimentary Jns 3014 514 Jnp IL007Naknek Formation, Pomeroy Arkose Member Massive light-gray arkose and arkosic conglomerate; minor interbeds of siltstone Late Jurassic Iliamna Sedimentary Jni 3014 514 Jnp KN005Naknek Formation, Pomeroy Arkose Member Massive light-gray arkose and arkosic conglomerate; minor interbeds of siltstone Late Jurassic Kenai Sedimentary Jni 3014 514 Jnp SV004Naknek Formation, Pomeroy Arkose Member Massive light-gray arkose and arkosic conglomerate; minor interbeds of siltstone Late Jurassic Seldovia Sedimentary Jni 3016 517 Jnc IL007Naknek Formation, Chisik Conglomerate Member Massive cobble-boulder conglomerate, mainly restricted to area adjacent to Iniskin Bay and Tuxedni Bay Late Jurassic Iliamna Sedimentary Jnc 3016 517 Jnc KN005Naknek Formation, Chisik Conglomerate Member Massive cobble-boulder conglomerate, mainly restricted to area adjacent to Iniskin Bay and Tuxedni Bay Late Jurassic Kenai Sedimentary Jnc 3020 518 Jcp IL007Chinitna Formation, Paveloff Siltstone Member Massive to thin-bedded gray arenaceous siltstone, weathers gray, large ellipsoidal concretions and lenticular beds of limestone, massive sandstone unit at base Late Jurassic Iliamna Sedimentary Js 3020 518 Jcp KN005Chinitna Formation, Paveloff Siltstone Member Massive to thin-bedded gray arenaceous siltstone, weathers gray, large ellipsoidal concretions and lenticular beds of limestone, massive sandstone unit at base Late Jurassic Kenai Sedimentary Js 3020 518 Jcp SV004Chinitna Formation, Paveloff Siltstone Member Massive to thin-bedded gray arenaceous siltstone, weathers gray, large ellipsoidal concretions and lenticular beds of limestone, massive sandstone unit at base Late Jurassic Seldovia Sedimentary Js 3025 121 Jc IL002Chinitna Formation Primarily dark-gray to brown massive arenacous siltstone containing a few sandstone interbeds and numerous limestone concretions. Unit is subdivided into members, however not on this map Middle Jurassic (Callovian) Abundant fossils, including many species of ammonites: Cadoceras, C. stenocadoceras, C. pseudocadoceras, Kepplerites, Kheraiceras, Lilloettia, and Gowericeras. Also especially known for Iniskinites and Chinitnites Iliamna Sedimentary Jc 3025 3030 Jc KN002Chinitna Formation Siltstone, limestone concretions, and sandstone Late Jurassic Kenai Sedimentary Jc 3025 32 Jc SV002Chinitna Formation Primarily dark-gray to brown massive arenacous siltstone containing a few sandstone interbeds and numerous limestone concretions. Unit is subdivided into members, however not on this map Late Jurassic (Callovian) Abundant fossils, including many species of ammonites: Cadoceras, C. stenocadoceras, C. pseudocadoceras, Kepplerites, Kheraiceras, Lilloettia, and Gowericeras. Also especially known for Iniskinites and Chinitnites Seldovia Sedimentary Jc 3030 519 Jct IL007Chinitna Formation, Tonnie Siltstone Member Massive to thin-bedded brownish-gray arenaceous siltstone, weathers red-brown, small yellowish-brown limestone concretions in parallel bands, minor sandstone at base Late Jurassic Iliamna Sedimentary Jc 3030 519 Jct KN005Chinitna Formation, Tonnie Siltstone Member Massive to thin-bedded brownish-gray arenaceous siltstone, weathers red-brown, small yellowish-brown limestone concretions in parallel bands, minor sandstone at base Late Jurassic Kenai Sedimentary Jc 3030 519 Jct SV004Chinitna Formation, Tonnie Siltstone Member Massive to thin-bedded brownish-gray arenaceous siltstone, weathers red-brown, small yellowish-brown limestone concretions in parallel bands, minor sandstone at base Late Jurassic Seldovia Sedimentary Jc 3150 130 Jk DI003Graywacke of Kulukak Bay A thick marine sedimentary unit referred to as "Weary graywacke" by Hoare and others, 1975. Consists of very hard graywacke and siltstone with local conglomerate. Middle to early Late Jurassic Buchia, Inoceramus, belemnites, and rare ammonite fragments ranging from Middle to early Late Jurassic age. Dillingham Sedimentary Jkw 3150 5312 Jk DI005Graywacke of Kulukak Bay A thick marine sedimentary unit referred to as "Weary graywacke" by Hoare and others, 1975. Mapped in the eastern part of the quadrangle by correlation with unit KJs of the adjacent Iliamna quadrangle. Typically consists of dark green or gray massive sMiddle to early Late Jurassic Rare fragmentary fossils, appearing to be possibly Buchia. Reported Jurassic fossils found by Unocal in 1959. Dillingham Sedimentary Jkw 3180 122 Jt IL002Tuxedni Group Light- to dark-gray and green graywacke, conglomerate, siltstone, and shale. Graywacke ranges from feldspathic to lithic to laumontitic; conglomerate composed mainly of volcanic clasts in a graywacke matrix. Unit is subdivided into Formation, however nMiddle Jurassic (Bajocian and Bathonian) Abundantly fossiliferous, containing ammonites and pelecypods. Key ammonites include Erycites, Tmetoceras, Sonninia, Stemmatoceras, Emileia, Stephanoceras, Chondroceras, and many others Iliamna Sedimentary Jtx 3180 3180 Jt KN002Tuxedni Formation Sandstone, siltstone, and limy concretions Middle Jurassic Kenai Sedimentary Jtx 3180 50 Jtu SV002Tuxedni Formation Light- to dark-gray and green graywacke, conglomerate, siltstone, and shale. Graywacke ranges from feldspathic to lithic to laumontitic; conglomerate composed mainly of volcanic clasts in a graywacke matrix. Unit is subdivided into Formation, however nMiddle to Late Jurassic (Bajocian to Callovian) Abundantly fossiliferous, containing ammonites and pelecypods. Key ammonites include Erycites, Tmetoceras, Sonninia, Stemmatoceras, Emileia, Stephanoceras, Chondroceras, and many others Seldovia Sedimentary Jtx 3181 520 Jtb IL007Tuxedni Group, Bowser Formation Heterogeneous assemblage of sandstone, conglomerate, shale and siltstone characterized by rapid facies changes. Massive light- to dark-gray sandstone and conglomerate are the dominant lithologic types on the Iniskin Peninsula. The sandstone and the conMiddle and Late Jurassic Abundantly fossiliferous, containing ammonites and pelecypods, the units can be divided into two faunal zones which correspond to the break between the Middle and Upper Jurassic. The lower faunal zone immediately overlies the unconformity with the Twist Iliamna Sedimentary Jtx 3181 520 Jtb KN005Tuxedni Group, Bowser Formation Heterogeneous assemblage of sandstone, conglomerate, shale and siltstone characterized by rapid facies changes. Massive light- to dark-gray sandstone and conglomerate are the dominant lithologic types on the Iniskin Peninsula. The sandstone and the conMiddle and Late Jurassic Abundantly fossiliferous, containing ammonites and pelecypods, the units can be divided into two faunal zones which correspond to the break between the Middle and Upper Jurassic. The lower faunal zone immediately overlies the unconformity with the Twist Kenai Sedimentary Jtx 3181 520 Jtb SV004Tuxedni Group, Bowser Formation Heterogeneous assemblage of sandstone, conglomerate, shale and siltstone characterized by rapid facies changes. Massive light- to dark-gray sandstone and conglomerate are the dominant lithologic types on the Iniskin Peninsula. The sandstone and the conMiddle and Late Jurassic Abundantly fossiliferous, containing ammonites and pelecypods, the units can be divided into two faunal zones which correspond to the break between the Middle and Upper Jurassic. The lower faunal zone immediately overlies the unconformity with the Twist Seldovia Sedimentary Jtx 3182 521 Jtt IL007Tuxedni Group, Twist Creek Siltstone Soft, poorly consolidated, thin-bedded to massive siltstone and silty shale as much 125-m-thick. The siltstone is dark-gray, weathering to dark-rusty brown and contains many thin beds of volcanic ash that weather a bright orange color. Small limestone Middle Jurassic Abundant ammonite fauna which includes Oppelia (Liroxyites), Megasphaerceras, Leptoshinctes, Lissoceras, and Normannites (Dettermanites) Iliamna Sedimentary Jtx 3182 521 Jtt KN005Tuxedni Group, Twist Creek Siltstone Soft, poorly consolidated, thin-bedded to massive siltstone and silty shale as much 125-m-thick. The siltstone is dark-gray, weathering to dark-rusty brown and contains many thin beds of volcanic ash that weather a bright orange color. Small limestone Middle Jurassic Abundant ammonite fauna which includes Oppelia (Liroxyites), Megasphaerceras, Leptoshinctes, Lissoceras, and Normannites (Dettermanites) Kenai Sedimentary Jtx 3182 521 Jtt SV004Tuxedni Group, Twist Creek Siltstone Soft, poorly consolidated, thin-bedded to massive siltstone and silty shale as much 125-m-thick. The siltstone is dark-gray, weathering to dark-rusty brown and contains many thin beds of volcanic ash that weather a bright orange color. Small limestone Middle Jurassic Abundant ammonite fauna which includes Oppelia (Liroxyites), Megasphaerceras, Leptoshinctes, Lissoceras, and Normannites (Dettermanites) Seldovia Sedimentary Jtx 3183 522 Jtc IL007Tuxedni Group, Cynthia Falls Sandstone Massive to thick-bedded graywacke sandstone and pebble conglomerate about 200-m-thick. The sandstone is medium- to coarse-grained, greenish-gray to dark-green, weathering mottled light-gray due to zeolites and has graded bedding. The sandstone consistsMiddle Jurassic The sparse fauna includes the ammonites Chondroceras and Stephanoceras as well as the pelecypods Inoceramus sp. and Mytilus sp. Iliamna Sedimentary Jtx 3183 522 Jtc KN005Tuxedni Group, Cynthia Falls Sandstone Massive to thick-bedded graywacke sandstone and pebble conglomerate about 200-m-thick. The sandstone is medium- to coarse-grained, greenish-gray to dark-green, weathering mottled light-gray due to zeolites and has graded bedding. The sandstone consistsMiddle Jurassic The sparse fauna includes the ammonites Chondroceras and Stephanoceras as well as the pelecypods Inoceramus sp. and Mytilus sp. Kenai Sedimentary Jtx 3183 522 Jtc SV004Tuxedni Group, Cynthia Falls Sandstone Massive to thick-bedded graywacke sandstone and pebble conglomerate about 200-m-thick. The sandstone is medium- to coarse-grained, greenish-gray to dark-green, weathering mottled light-gray due to zeolites and has graded bedding. The sandstone consistsMiddle Jurassic The sparse fauna includes the ammonites Chondroceras and Stephanoceras as well as the pelecypods Inoceramus sp. and Mytilus sp. Seldovia Sedimentary Jtx 3184 523 Jtf IL007Tuxedni Group, Fitz Creek Siltstone Thick sequence of massive, bluish dark-gray, arenaceous coarse- to fine-grained siltstone that commonly weathers rusty orange and contains many small limestone concretions. Interbedded are fine-grained sandstone and, locally, conglomerate interbeds. InMiddle Jurassic This unit is abundantly fossiliferous and is the first unit of the Tuxedini Group where ammonites are more numerous than pelecypods. A few non-diagnostic brachiopods are also present. The ammonites include Normannites, Teloceras, and Chondroceras and m Iliamna Sedimentary Jtx 3184 523 Jtf KN005Tuxedni Group, Fitz Creek Siltstone Thick sequence of massive, bluish dark-gray, arenaceous coarse- to fine-grained siltstone that commonly weathers rusty orange and contains many small limestone concretions. Interbedded are fine-grained sandstone and, locally, conglomerate interbeds. InMiddle Jurassic This unit is abundantly fossiliferous and is the first unit of the Tuxedini Group where ammonites are more numerous than pelecypods. A few non-diagnostic brachiopods are also present. The ammonites include Normannites, Teloceras, and Chondroceras and m Kenai Sedimentary Jtx 3184 523 Jtf SV004Tuxedni Group, Fitz Creek Siltstone Thick sequence of massive, bluish dark-gray, arenaceous coarse- to fine-grained siltstone that commonly weathers rusty orange and contains many small limestone concretions. Interbedded are fine-grained sandstone and, locally, conglomerate interbeds. InMiddle Jurassic This unit is abundantly fossiliferous and is the first unit of the Tuxedini Group where ammonites are more numerous than pelecypods. A few non-diagnostic brachiopods are also present. The ammonites include Normannites, Teloceras, and Chondroceras and m Seldovia Sedimentary Jtx 3185 524 Jtg IL007Tuxedni Group, Gaikema Sandstone Resistant, cliff-forming, massive to thin-bedded graywacke sandstone and cobble conglomerate showing graded bedding. Conglomerate is confined to the Iniskin Peninsula, clasts in it consist of red and green felsic volcanic rocks, aphanitic igneous rocks Middle Jurassic Fossiliferous throughout, containing pelcypods Meleagrinella, Trigonia, and Inoceramus and ammonites Witchellia(?), Stephanceras and locally, Sonninia (Papilliceras), Lissoceras, and Emileia Iliamna Sedimentary Jtx 3185 524 Jtg KN005Tuxedni Group, Gaikema Sandstone Resistant, cliff-forming, massive to thin-bedded graywacke sandstone and cobble conglomerate showing graded bedding. Conglomerate is confined to the Iniskin Peninsula, clasts in it consist of red and green felsic volcanic rocks, aphanitic igneous rocks Middle Jurassic Fossiliferous throughout, containing pelcypods Meleagrinella, Trigonia, and Inoceramus and ammonites Witchellia(?), Stephanceras and locally, Sonninia (Papilliceras), Lissoceras, and Emileia Kenai Sedimentary Jtx 3185 524 Jtg SV004Tuxedni Group, Gaikema Sandstone Resistant, cliff-forming, massive to thin-bedded graywacke sandstone and cobble conglomerate showing graded bedding. Conglomerate is confined to the Iniskin Peninsula, clasts in it consist of red and green felsic volcanic rocks, aphanitic igneous rocks Middle Jurassic Fossiliferous throughout, containing pelcypods Meleagrinella, Trigonia, and Inoceramus and ammonites Witchellia(?), Stephanceras and locally, Sonninia (Papilliceras), Lissoceras, and Emileia Seldovia Sedimentary Jtx 3186 525 Jtr IL007Tuxedni Group, Red Glacier Formation Thin-bedded to massive, red-brown weathering dark-gray to moderate olive-gray siltstone in the concentrated in the upper part of the unit and consisting of about 40 percent of the Formation. The siltstone is highly arenaceous and locally contains lenticMiddle Jurassic The Red Glacier Formation is most abundantly fossiliferous in its upper parts, no fossils are known from the lower 2000 feet of the unit. Pelcypods include Meleagrinella, Trigonia, Inoceramus, Camptonectes, and Pleuromya. Ammonites occur in two distinc Iliamna Sedimentary Jtx 3186 525 Jtr KN005Tuxedni Group, Red Glacier Formation Thin-bedded to massive, red-brown weathering dark-gray to moderate olive-gray siltstone in the concentrated in the upper part of the unit and consisting of about 40 percent of the Formation. The siltstone is highly arenaceous and locally contains lenticMiddle Jurassic The Red Glacier Formation is most abundantly fossiliferous in its upper parts, no fossils are known from the lower 2000 feet of the unit. Pelcypods include Meleagrinella, Trigonia, Inoceramus, Camptonectes, and Pleuromya. Ammonites occur in two distinc Kenai Sedimentary Jtx 3186 525 Jtr SV004Tuxedni Group, Red Glacier Formation Thin-bedded to massive, red-brown weathering dark-gray to moderate olive-gray siltstone in the concentrated in the upper part of the unit and consisting of about 40 percent of the Formation. The siltstone is highly arenaceous and locally contains lenticMiddle Jurassic The Red Glacier Formation is most abundantly fossiliferous in its upper parts, no fossils are known from the lower 2000 feet of the unit. Pelcypods include Meleagrinella, Trigonia, Inoceramus, Camptonectes, and Pleuromya. Ammonites occur in two distinc Seldovia Sedimentary Jtx 3220 132 Jlvs TA006Volcanic and sedimentary rocks Marine unit of mafic flows, some pillow structure, volcanic breccias, and massive fine- to medium-grained volcanogenic sedimentary rocks. Fractures commonly coated with laumontite Early Jurassic Weyla pelecypods of Early Jurassic age. Taylor MountainsSedimentary JTrtk 3220 1932 Jlvs TA019Volcanic and sedimentary rocks Marine unit of mafic flows, some pillow structure, volcanic breccias, and massive fine- to medium-grained volcanogenic sedimentary rocks. Fractures commonly coated with laumontite Early Jurassic Weyla pelecypods of Early Jurassic age. Taylor MountainsSedimentary JTrtk 3250 124 Jtk IL002Talkeetna Formation Mainly volcanic breccia, agglomerate, lava flows, and tuff. Sedimentary rocks locally interbedded but are minor. Informally divided into three members, which correlate with formal members elsewhere. Early Jurassic -- Sinemurian to Pliensbachian Nondiagnostic in Iliamna quadrangle, good fossils known from northern exposures in Talkeetna Mountains. Iliamna Igneous JTrtk 3250 529 Jtku IL007Talkeetna Formation, undivided Tuff, sandstone, agglomerate, breccia and some lava flows Early Jurassic Iliamna Igneous JTrtk 3250HFS 2825 KJu KN002Metasedimentary rocks (undivided) Weakly metamorphosed slate and graywacke; locally includes volcanic and intrusive rocks, undivided. Consists of contact metamorposed Talkeetna Formation according to Detterman and others (1976, KN010). Cretaceous and (or) Jurassic Kenai Metamorphic KJfm 3250 3250 Jtk KN002Talkeetna Formation Volcanic breccia, tuff, agglomerate, and aphanitic lava flows; as mapped, locally includes Kamishak Formation in Ilianna Quad Early Jurassic Kenai Igneous JTrtk 3250 529 Jtku KN005Talkeetna Formation, undivided Tuff, sandstone, agglomerate, breccia and some lava flows Early Jurassic Kenai Igneous JTrtk 3250 622 bpT KN006Jurassic bedrock Volcanic flows, tuffs, and breccias, metamorphic equivalents, and granodiorite. Talkeetna Formation and other units Jurassic Kenai Igneous JTrtk 3250 904 Jv KN009Volcanic rocks Volcanic rocks, locally includes sedimentary rocks Jurassic Kenai Igneous 3250HFS 1010 Mz KN010Metamorphic rocks Schist, hornfels, and amphibolite, contact metamorphosed Talkeetna Formation Mesozoic Kenai Metamorphic 3250 1206 sv KN012Sedimentary and volcanic rocks Cheifly Jurassic volcanic rocks; locally includes Mesozoic and Cenozoic sedimentary and volcanic rocks Cenozoic and Mesozoic Kenai Sedimentary 3250 5124 Jtk LC005Talkeetna Formation Mainly volcanic breccia, agglomerate, lava flows, and tuff. Sedimentary rocks locally interbedded but are minor. Informally divided into three members, which correlate with formal members elsewhere. Early Jurassic -- Sinemurian to Pliensbachian Nondiagnostic in Iliamna quadrangle, good fossils known from northern exposures in Talkeetna Mountains. Lake Clark Igneous JTrtk 3250 603 JTr LC006Talkeetna Formation? Jurassic volcanic and volcaniclastic rocks Jurassic and Triassic Lake Clark Igneous JTrtk 3250 729 Jtku LC007Talkeetna Formation, undivided Tuff, sandstone, agglomerate, breccia and some lava flows Early Jurassic Lake Clark Igneous JTrtk 3250 67 Jt SV002Talkeetna Formation Mainly volcanic breccia, agglomerate, lava flows, and tuff. Sedimentary rocks locally interbedded but are minor. Informally divided into three members, which correlate with formal members elsewhere. Includes informally named Pogibshi Formation on eastEarly Jurassic (Hettangian to Toarcian) Seldovia Igneous JTrtk 3250 529 Jtku SV004Talkeetna Formation, undivided Tuff, sandstone, agglomerate, breccia and some lava flows Early Jurassic Seldovia Igneous JTrtk 3251 526 Jtkh IL007Talkeetna Formation, Horn Mountain Tuff Member Mottled andesitic tuff, tuffaceous sandstone, and siltstone, locally contains andesitic flows Early Jurassic Iliamna Sedimentary JTrtk 3251 526 Jtkh KN005Talkeetna Formation, Horn Mountain Tuff Member Mottled andesitic tuff, tuffaceous sandstone, and siltstone, locally contains andesitic flows Early Jurassic Kenai Sedimentary JTrtk 3252 527 Jtkp IL007Talkeetna Formation, Portage Creek Agglomerate Member Massive pink agglomerate and some volcanic breccia; minor andesitic flows, locally metasedimentary rock Early Jurassic Iliamna Igneous JTrtk 3252 527 Jtkp KN005Talkeetna Formation, Portage Creek Agglomerate Member Massive pink agglomerate and some volcanic breccia; minor andesitic flows, locally metasedimentary rock Early Jurassic Kenai Igneous JTrtk 3253 528 Jtkm IL007Talkeetna Formation, Marsh Creek Breccia Member Massive green volcanic breccia, lava flows, in part of submarine origin, interbedded with argillite and meta tuff, low rank metamorphism mainly confined to lower part Early Jurassic Iliamna Igneous JTrtk 3253 528 Jtkm KN005Talkeetna Formation, Marsh Creek Breccia Member Massive green volcanic breccia, lava flows, in part of submarine origin, interbedded with argillite and meta tuff, low rank metamorphism mainly confined to lower part Early Jurassic Kenai Igneous JTrtk 3260 1915 MzPzgps TA019Phyllite argillite, and chert Gray to black phyllite or slaty argillite, occasionally calcareous or sulfide-bearing along fault zones Early Jurassic or Late Triassic? Age based on Box and others (1993) Bethel map, Early Jurassic radiolarians Taylor MountainsSedimentary 3380 125 Jtr IL002Trondhjemite Medium- to coarse-grained, light-gray muscovite bearing trondhjemite Late Jurassic K-Ar muscovite age of 145 Ma Iliamna Igneous Jtr 3380 1204 Jth KN012Trondjemite Trondjemite Jurassic Kenai Igneous 3380 202 Ji2 LC002Jurassic intrusive rocks -- Unit 2 Trondhjemite Medium- to coarse-grained, seriate, leucocratic trondhjemite Jurassic A sample from the Iliamna quadrangle yielded a 145 Ma K-Ar age on muscovite Lake Clark Igneous Jtr 3380 1104 Jth LC011Trondjemite Trondjemite Jurassic Lake Clark Igneous 3400 809 Jg IL008Granitic rocks Granitic rocks of the Alaska-Aleutian Range batholith Jurassic Iliamna Igneous 3400 11340Jg KN011Granitic rocks Granitic rocks of the Alaska-Aleutian Range batholith Jurassic Kenai Igneous 3400 602 Jg LC006Jurassic granitic rocks Jurassic granitic rocks Jurassic Lake Clark Igneous Jqd 3400 10340Jg LC010Granitic rocks Granitic rocks of the Alaska-Aleutian Range batholith Jurassic Lake Clark Igneous 3401 115 J(?)f SV002Felsite Fine-grained aphanitic, light gray felsite Jurassic? or early Tertiary? Seldovia Igneous Jgr 3402 126 Jqm IL002Quartz monzonite Medium-grained, light-gray with a pinkish cast quartz monzonite, locally includes granodiorite and trondhjemite. Late Jurassic Iliamna Igneous Jgd 3402 532 Jqm IL007Quartz monzonite Medium- to coarse-grained pink to gray granitic-textured quartz monzonite Jurassic Iliamna Igneous Jgd 3402 536 p IL007Pegmatite or aplite dikes Pegmatite or aplite dikes Jurassic Iliamna Igneous 3402 3402 Jgd KN002Quartz monzonite Quartz monzonite Jurassic Kenai Igneous Jgd 3402 532 Jqm KN005Quartz monzonite Medium- to coarse-grained pink to gray granitic-textured quartz monzonite Jurassic Kenai Igneous Jgd 3402 203 Ji3 LC002Jurassic intrusive rocks -- Unit 3 Granodiorite Whitish-gray, medium-grained, seriate biotite granodiorite. Jurassic Lake Clark Igneous Jgd 3402 738 pg LC007Pink quartz monzonite dikes Pink quartz monzonite dikes Jurassic Lake Clark Igneous 3403 127 Jqd IL002Quartz diorite Medium- to coarse-grained, light-gray quartz diorite that contains biotite and hornblende, locally includes small areas of diorite and granodiorite. Late Jurassic Multiple K-Ar ages ranging form 168 Ma on hornblende to 152 Ma on biotite. Analytically best ages cluster around 155 to 158 Ma Iliamna Igneous Jqd 3403 533 Jqd IL007Quartz diorite Mainly biotite-hornblende-quartz dioriite Jurassic Iliamna Igneous Jqt 3403 3403 Jqd KN002Quartz diorite, diorite, and granodiorite Quartz diorite, diorite, and granodiorite Jurassic Kenai Igneous Jqd 3403 201 Ji1 LC002Jurassic intrusive rocks -- Unit 1 Tonalite Medium-grained tonalite and quartz diorite, locally foliated. Two small exposures of gabbro and diorite included in unit. Jurassic Lake Clark Igneous Jqd 3404 533 Jqd KN005Quartz diorite Mainly biotite-hornblende-quartz dioriite Jurassic Kenai Igneous Jqt 3404 537 di KN005Quartz diroite dikes Quartz diorite dikes Jurassic Kenai Igneous Jqt 3404 903 Ju KN009Plutonic rocks, undivided Plutonic rocks, undivided; chiefly tonalite and trondhjemite Jurassic Kenai Igneous 3404 1205 JT KN012Tonalite Tonalite, includes hornblendite, hornblende-biotite quartz diorite, and rare granodiorite, quartz monzonite, and granite Jurassic Kenai Igneous 3404 733 Jqd LC007Quartz diorite Mainly biotite-hornblende-quartz dioriite Jurassic Lake Clark Igneous Jqt 3404 1105 JT LC011Tonalite Tonalite, includes hornblendite, hornblende-biotite quartz diorite, and rare granodiorite, quartz monzonite, and granite Jurassic Lake Clark Igneous 3404 111 Jd SV002Diorite of Point Bede Fine- to medium-grained nonfoliated quartz diorite. Jurassic? Seldovia Igneous Jqt 3404 116 Jto SV002Tonalite of Dogfish Bay Medium-grained nonfoliated tonalite. Jurassic? Seldovia Igneous Jqt 3405 128 Jd IL002Diorite Medium- to coarse-grained diorite, locally includes small areas of quartz diorite and gabbro; numerous xenoliths. Late Jurassic Iliamna Igneous Jmu 3420 534 la IL007Lamprophyre dikes Lamprophyre dikes Jurassic Iliamna Igneous Ji 3420 535 b IL007Basalt dikes Basalt dikes Jurassic Iliamna Igneous Ji 3420 534 la KN005Lamprophyre dikes Lamprophyre dikes Jurassic Kenai Igneous Ji 3420 734 la LC007Lamprophyre dikes Lamprophyre dikes Jurassic Lake Clark Igneous Ji 3450 500 mi DI002Mafic igneous rocks Predominantly diabase, probably intrusive. Associated with silicious sedimentary and extrusive rocks of now abandoned Gemuk Group of questioned Jurassic age. Jurassic? Dillingham Igneous Jvab 3495 129 Jm IL002Mafic and ultramafic plutonic rocks Gabbro, hornblende gabbro, hornblendite, and pyroxenite Early Jurassic K-Ar age of 183 Ma on hornblende Iliamna Igneous Jmu 3610 10 Jsm SV002Seldovia metamorphic complex Marble, quartzite, garnet-mica schist, and glaucophane-bearing amphibolite Early Jurassic 191.1 and 191.7 Ar-Ar on white mica and 191.9 Ar-Ar on hornblende Seldovia Metamorphic Jsch 3821 3821 eJTrl TA008Limestone, shale, and chert Cream colored to dark-gray, limestone, shale, and chert. Early Jurassic? and Triassic -- Norian Triassic (Norian) fossils collected by Blodgett amd Blome Taylor MountainsSedimentary eJTrl 4011 2004 Trgl TA020Gemuk Group, limestone and chert Interbedded limestone, fossiliferous argillaceous limestone, and gray-green chert Triassic Monotis and Halobia Taylor MountainsSedimentary 4012 4020 Trlc TA008Triassic limestone and chert Cream colored to dark-gray, limestone, and chert, locally interbedded in thin repeating beds. Triassic (Norian) Triassic (Norian) fossils collected by Blodgett amd Blome Taylor MountainsSedimentary Trk? 4012 4023 Trlt TA008Limestone Newly described limestone, faunally distinct from limestone and chert section. Only known from the TA D-2 and D-3 quadrangles Triassic Relatively abundant fauna, to be described Taylor MountainsSedimentary 4020 4020 Trk KN002Kamishak Formation Limestone, grey to black chert, and porcellanite Late Triassic Kenai Sedimentary Trk 4020 1215 St LC012Limestone Highly fractured dark-gray limestone and chert Silurian Contains stromatoporoids (undet.), solitary rugose coral, Pentameris(?) sp. and undet. rynchonelloid brachiopods at one fossil locality Lake Clark Sedimentary 4020 60 JTrp SV002Port Graham Formation of Kelley (1980) Dark-gray, carbonaceous limestone and silty limestone, also includes tuff, tuffaceous sedimentary rocks, and chert. Most of unit considered Norian in age. Early Jurassic and Late Triassic Bivalves of Late Triassic (Norian) age Seldovia Sedimentary JTrta 4022 130 Trku IL002Kamishak Formation -- Ursus Member Thin-bedded, light-gray limestone (locally dolomitic), and minor interbedded gray chert and porcellanite and minor tuff. Limestone is fine-grained biomicrite. Depositional environment was moderate to high-energy, shallow water. Unit cut by abundant diLate Triassic? or Early Jurassic? None definitive Iliamna Sedimentary Trk 4023 131 Trkm IL002Kamishak Formation -- Middle Member Thin- to medium-bedded, dark-gray to black limestone and calcilutite (locally dolomitic), and minor black chert and gray tuff. Limestone is fine-grained microsparite. Calcite is locally altered to chert, suggesting a deep-basin environment. Unit cut bLate Triassic (middle to late Norian) Corals: Koilocenia cf. K. andreai (Volz), Oppelismilia cf. O. mojsvari (Frech), and Thamnasteria sp.; hydrozoan Heterastridium cf. H. conglobotum Reuss and Monotis subcircularis Gabb Iliamna Sedimentary Trk 4024 132 Trkb IL002Kamishak Formation -- Briun Limestone Member Massive to thin-bedded, light- to dark-gray limestone; coral and echinoid bioherms, banded green and white chert. Environment was apparently high energy, shallow water. Unit cut by abundant dikes and sills either related to the Cottonwood Bay GreenstonLate Triassic (Norian) Halobia cf. H. dilatata and Monotis(?) sp. Iliamna Sedimentary Trk 4035 301 KCg2 DI002Gemuk Group -- Triassic limestone Generally white to cream colored, recrystallized limestone, however locally is dark gray and only finely crystalline. Possibly fault bounded occurrences. Triassic (Norian) Triassic (Norian) fossils collected by Mertie Dillingham Sedimentary Trk? 4035 135 Trvs DI003Volcanic and sedimentary rocks Marine unit consisting of chert, tuffaceous cherty rocks, argillite, siltstone, volcanic wacke, conglomerate, limestone, and mafic flows and breccias. Triassic Pelecypods of Late Triassic age Dillingham Sedimentary Trcg 4035 184 KCg2 TA002Gemuk Group -- Triassic limestone Generally white to cream colored, recrystallized limestone, however locally is dark gray and only finely crystalline. Possibly fault bounded occurrences. Triassic (Norian) Triassic (Norian) fossils collected by Mertie Taylor MountainsSedimentary Trk? 4050 5050 Trsh LC005Gray shale and gray volcaniclastic sandstone Gray shale and gray volcaniclastic sandstone. Inferred on basis of Eakins and others (1978). Triassic Lake Clark Sedimentary 4050 1212 Ssh LC012Gray shale and gray volcaniclastic sandstone Gray shale and gray volcaniclastic sandstone Silurian Lake Clark Sedimentary 4215Q 1515 Trb TA015Volcanic rocks Volcanic rocks within former Gemuk Group. Inferred from extrapolation of Hoare and Condon field notes. Triassic Taylor MountainsIgneous Trb 4215 17001KTrPCg TA017Gemuk Group -- basalt Volcanic rocks comprising at least 5 separate flows, locally as much as 200 feet think interbedded with cherty siltstone. Thought to occur stratigraphically near top of Gemuk section. Triassic Associated Monotis and Halobia, late Triassic Taylor MountainsIgneous Trb 4215 19001Trv TA019Basalt Volcanic rocks comprising at least 5 separate flows, locally as much as 200 feet think interbedded with cherty siltstone. Thought to occur stratigraphically near top of Gemuk section. Triassic Associated Monotis and Halobia, late Triassic Taylor MountainsIgneous Trb 4425 5025 Trv DI005Mafic igneous rocks Predominantly basaltic flows and volcaniclastic rocks. May be equilvalent to the Chilikadrotna Greenstone of Triassic age. Jurassic? or Triassic? Dillingham Igneous Trc 4425 133 Trc IL002Cottonwood Bay Greenstone Dark-gray to dark-green porphyritic to amygdaloidal basaltic flows altered to greenstone. In general, slightly more metamorphosed than Nikolai Greenstone. Late Triassic (pre-Norian?) Iliamna Metamorphic Trc 4425 220 Sc LC002Chilikadrotna Greenstone Basalt, andesite, chert, limestone, and tuffaceous sedimentary rock, all weakly metamorphosed. About 60 percent of unit is metabasalt Triassic Unit originally assigned a Silurian age, was later found to be in error and is now considered Triassic. Lake Clark Igneous Trc 4425 301 JTrv LC003Chilikadrotna Greenstone Basaltic pillows and flows, andesitic breccia, chert, and limestone. Jurassic and Triassic Lake Clark Igneous Trc 4425 5425 Sg LC005Greenstone, dark-green basalt Dark-green basalt having relict pillow structures, containes minor red and balck chert. Inferred on basis of Eakins and others (1978). Silurian Lake Clark Metamorphic 4425 604 JTrca LC006 Unknown Jurassic and Triassic Lake Clark Metamorphic Trc 4425Q 605 JTrca? LC006 Unknown Jurassic and Triassic Lake Clark Metamorphic Trc 4425 625 Trcb LC006Cottonwood Bay Greenstone Greenstone Triassic Lake Clark Igneous Trc 4425 626 Trcb + MzPzpLC006Cottonwood Bay Greenstone and ? Greenstone and ? Triassic Lake Clark Metamorphic Trc 4425 627 Trcb? LC006Cottonwood Bay Greenstone Greenstone Triassic Lake Clark Igneous Trc 4425 1213 Sg LC012Greenstone, dark-green basalt Dark-green basalt having relict pillow structures, containes minor red and balck chert Silurian Lake Clark Metamorphic 4425 1214 Spb LC012Greenstone, purple basalt Purple basalt and hematite rich sandstone Silurian Lake Clark Metamorphic 4425 15425Trv TA015Mafic igneous rocks Predominantly mafic flows and volcaniclastic rocks. May be associated with the Chilikadrotna Greenstone of Triassic age from the Lake Clark quadrangle. Triassic? Taylor MountainsIgneous Trc 4710 186 KCg TA002Gemuk Group -- undivided Primarily coarse-grained clastic rocks containing some fine-grained cherty and volcanic material. Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Taylor MountainsSedimentary MzPzgs 4710HFS 1204 h TA012Hornfels Contact metamorphic zones adjacent to igneous intrusive rocks. (Note, in this quadrangle, probably includes both Kuskokwim and Gemuk units, hence source rock are in part older than Cretaceous). Cretaceous Taylor MountainsMetamorphic MzPzgs 4710 1205 s TA012Sedimentary rocks Interbedded graywacke and shale, with local interbeds of argillite and conglomerate. In this quadrangle, most certainly includes rocks of the Gemuk Group and to a lesser extent Kuskkwim Group. Cretaceous Taylor MountainsSedimentary MzPzgs 4710 2003 Trg TA020Gemuk Group, undifferentiated Graywacke, siltstone and lesser amounts of chert, tuff, shale, and black limestone Triassic Taylor MountainsSedimentary 4711 2005 Trgv TA020Gemuk Group, sedimentary and volcanic rocks Graywacke, siltstone, and volcanic rocks, including lava and tuff, interbedded with black shale, black limestone, argillaceous limestone, and chert Triassic Monotis and Halobia Taylor MountainsSedimentary 4880 112 Mg SV002Gabbro Dark-green, medium- to coarse-grained gabbro and minor leucogabbro and plagiogranite. Associated with McHugh Complex as fault-bounded bodies. Mesozoic Seldovia Igneous Mzm 4890 110 Mu SV002Ultramafic plutonic rocks Predominantly layered, variably serpentinized dunite containing rare to locally abundant layers of chromitite and pyroxenite and fault slices of garnet pyroxenite and serpintinite. Associated with McHugh Complex as fault-bounded bodies. Mesozoic Seldovia Igneous Mzum 4950 303 KCg4 DI002Gemuk Group -- Mississippian(?) rocks Consists of massive and thin-bedded chert interbedded with siltstone and graywacke (generally calcareous), thin-bedded limestone, and minor mafic volcanic rocks. Chert is black, white, and gray and specifically not green, which is characteristic of younMississippian? Dillingham Sedimentary MzPzm 4950 145 MzPz DI003Mesozoic and Paleozoic rocks, undivided Thick, widespread, marine unit consisting of volcanic and sedimentary rocks ranging in age from Early (?) Ordovician to Early Cretaceous. Unit consists of thin-bedded to massive tuffaceous cherts and siltstones, argillite, graywacke, pebble-cobble conglEarly Cretaceous to Early? Ordovician Limestones commonly contain Permian fossils Dillingham Sedimentary MzPzm 4950 5145 MzPz DI005Mesozoic and Paleozoic rocks, undivided Thick, widespread, marine unit consisting of volcanic and sedimentary rocks ranging in age from Early (?) Ordovician to Early Cretaceous. Unit consists of thin-bedded to massive tuffaceous cherts and siltstones, argillite, graywacke, pebble-cobble conglEarly Cretaceous to Early? Ordovician Limestone commonly contains Permian fossils Dillingham Sedimentary MzPzm 4950 7145 MzPz DI007Mesozoic and Paleozoic rocks, undivided Thick, widespread, marine unit consisting of volcanic and sedimentary rocks ranging in age from Early (?) Ordovician to Early Cretaceous. Unit consists of thin-bedded to massive tuffaceous cherts and siltstones, argillite, graywacke, pebble-cobble conglEarly Cretaceous to Early? Ordovician Limestones commonly contain Permian fossils Dillingham Sedimentary MzPzm 4950 182 KCg4 TA002Gemuk Group -- Mississippian(?) rocks Consists of massive and thin-bedded chert interbedded with siltstone and graywacke (generally calcareous), thin-bedded limestone, and minor mafic volcanic rocks. Chert is black, white, and gray and specifically not green, which is characteristic of younMississippian? Taylor MountainsSedimentary MzPzm 4950 182 MzPz TA003Predominantly graywacke, fractured argillite, and chert (undivided) Predominantly graywacke, fractured argillite, and chert (undivided) Mississippian? Taylor MountainsSedimentary MzPzm 4950 6182 MzPz TA006Mesozoic and Paleozoic rocks, undivided Thick, widespread, marine unit consisting of volcanic and sedimentary rocks ranging in age from Early (?) Ordovician to Early Cretaceous. Unit consists of thin-bedded to massive tuffaceous cherts and siltstones, argillite, graywacke, pebble-cobble conglEarly Cretaceous to Early? Ordovician Limestones commonly contain Permian fossils Taylor MountainsTectonite MzPzm 4950 1901 Mzm TA019Melange Two or more rock types occuring in close proximity, typically tightly folded, sheared, and/or altered, including basalt (+/- pillows), gabbro, greywacke, shale, siltstone, limestone, and dolomite. Mesozoic? Taylor MountainsTectonite 5060 1300 KCg1 DI002Gemuk Group -- massive coarse-grained clastic rocks Massive, coarse-grained sandstone, quartzite, and conglomerate. Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Dillingham Sedimentary TrDs 5060 2300 KCg1 DI002Gemuk Group -- bedded clastic rocks Well-bedded, fine-grained sedimentary rocks, based on airphoto interpretation. Probably Cretaceous to Triassic Early Cretaceous (Valanginian), Jurassic, and Triassic Dillingham Sedimentary TrDs 5200 616 MzPzp LC006Metamorphic rocks? Metamorphic rocks? Mesozoic and Paleozoic Lake Clark Metamorphic 5200 1211 MzPzs LC012Biotite-feldspar-quartz schist Biotite-feldspar-quartz schist, locally actinolite-feldspar-quartz schist or garnet-feldspar-quartz schist. Mesozoic and Paleozoic Lake Clark Metamorphic 5220 123 Jmg IL002Migmatite Admixture of intrusive and metamorphic rocks, grading from gneissic to schistose texture, exposed along east margin of Alaska-Aleutian Range batholith. Middle and Early Jurassic Iliamna Metamorphic ? 5220 140 JPk IL002Kakhonak Complex Exposed chiefly as roof pendants in Alaska-Aleutian Range batholith and consists of schist, gneiss, quartzite, marble, phyllite, argillite, and slate. Greenschist facies metamorphic grade. Metamorphic rocks are thought to equivalent to Jurassic and TriJurassic, Triassic, and Permian? Iliamna Metamorphic JPzk 5220 530 Trm IL007Metamorphic rocks, undivided Metalimestone, argillite, quartzite, metatuff, greenstone, and phyllite; may in part be equivalent to the Kamishak Formation Late? Triassic Iliamna Metamorphic Trk 5220 811 Jm IL008Metamorphic rocks Metamorphic rocks, undifferentiated Jurassic Iliamna Metamorphic 5220 530 Trm KN005Metamorphic rocks, undivided Metalimestone, argillite, quartzite, metatuff, greenstone, and phyllite; may in part be equivalent to the Kamishak Formation Late? Triassic Kenai Metamorphic Trk 5220 906 as KN009Amphibolite Amphibolite, locally includes sedimentary rocks early Mesozoic? Kenai Metamorphic 5220 302 TrPztc LC003Tlikakila Complex A diverse complex of metamorphosed and highly deformed rocks, whose protoliths include calcerous to siliceous clastic rocks, limestone, thin-bedded chert, massive basalt, massive to layered gabbro and pyroxenite, and ultramafic rocks. Most of complex meTriassic to Paleozoic Late Triassic megafossils and conodonts from limestone; clearly a protolith age. Lake Clark Metamorphic JPzk 5220 402 TrPztc LC004Tlikakila Complex A diverse complex of metamorphosed and highly deformed rocks, whose protoliths include calcerous to siliceous clastic rocks, limestone, thin-bedded chert, massive unpillowed basalt, massive to layered gabbro and pyroxenite, and serpentinized ultramafic rTriassic to Paleozoic Lake Clark Metamorphic JPzk 5220HFS 619 TC LC006Tlikakila Complex Complex assemblage of metamorphiosed and hornfels(?) volcanic and sedimentary rocks Jurassic and older? Lake Clark Tectonite JPzk 5240 210 MzPzm LC002Metamorphosed mafic volcanic rocks, phyllite, schist, quartzite, marble, calc-silcate rocks, serpentinite, gabbro, and chertMetamorphosed mafic volcanic rocks, phyllite, schist, quartzite, marble, calc-silcate rocks, serpentinite, gabbro, and chert. Mixed unit of varying affinity and protolith and metamorphic age. Dominant rock of unit is metamorphosed mafic volcanic rocks Mesozoic and Paleozoic Lake Clark Metamorphic MzPzb 5240Q 55240MzPzm LC005Mafic metamorphic rocks? Mafic rocks? Mesozoic and Paleozoic Lake Clark Metamorphic MzPzb 5240Q 614 M LC006Mafic metamorphic rocks? Mafic rocks? Mesozoic Lake Clark Metamorphic MzPzb 5240 615 MzPzm LC006Mafic metamorphic rocks? Mafic rocks? Mesozoic and Paleozoic Lake Clark Metamorphic MzPzb 5380 1904 ePzc DI005Black chert Predominantly of black and gray chert but also includes rare white, buff, red, or green bedded to massive chert. It is occasionally vitreous, banded or fractured, and is interbedded with minor amounts of limestone, amygdaloidal basalt, and thin pitted cEalry Paleozoic Hoare and Jones (1981) report Lower Paleozoic (Devonian? and pre-Devonian) and Paleozoic(?) radiolarians from this unit as well as Permian megafossils. Dillingham Metamorphic 5380 1904 ePzc TA019Black chert Predominantly of black and gray chert but also includes rare white, buff, red, or green bedded to massive chert. It is occasionally vitreous, banded or fractured, and is interbedded with minor amounts of limestone, amygdaloidal basalt, and thin pitted cEalry Paleozoic Hoare and Jones (1981) report Lower Paleozoic (Devonian? and pre-Devonian) and Paleozoic(?) radiolarians from this unit as well as Permian megafossils. Taylor MountainsMetamorphic 5730 140 Pl DI003Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Dillingham Sedimentary Pls 5730 7730 Pl DI007Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Dillingham Sedimentary Pls 5730 6140 Pl TA006Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Taylor MountainsSedimentary Pls 5730 15140Pl TA015Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Taylor MountainsSedimentary Pls 5730 17140Pl TA017Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Taylor MountainsSedimentary Pls 5730 1911 Pl TA019Limestone Thin, widespread, fine-grained, crystalline limestone. Fetid odor. Generally tuffaceous, locally cherty. Permian Reported brachipods and crinoids Taylor MountainsSedimentary Pls 5745 1902 Pcs DI005Clastic rocks Predominantly fine to coarse-grained, rarely conglomeratic or brecciated, light gray, greenish-gray, or black streaky, slaty, phyllitic, micaceous or silty bedded to massive graywacke. Cigar sized and shaped pits, boudins, or slightly hornfelsed in somePermian? Associated Permian limestone containing Atomodesma Dillingham Sedimentary 5745 1902 Pcs TA019Clastic rocks Predominantly fine to coarse-grained, rarely conglomeratic or brecciated, light gray, greenish-gray, or black streaky, slaty, phyllitic, micaceous or silty bedded to massive graywacke. Cigar sized and shaped pits, boudins, or slightly hornfelsed in somePermian? Associated Permian limestone containing Atomodesma Taylor MountainsSedimentary 5810 302 KCg3 DI002Gemuk Group -- Permian volcanic rocks Predominantly dark-green to black, altered mafic volcanic rocks having abundant amygdules. Volcanic breccia, calcareous tuff, and pillow lava constitute lower beds, pillow lavas in middle, and phyllitic calcareous tuff and tuffaceous limestone constitutPermian? and Triassic? Dillingham Igneous Pv 5810 137 Pv DI003Gemuk Group -- Permian volcanic rocks Predominantly dark-green to black, altered mafic volcanic rocks having abundant amygdules. Volcanic breccia, calcareous tuff, and pillow lava constitute lower beds, pillow lavas in middle, and phyllitic calcareous tuff and tuffaceous limestone constitutPermian? and Triassic? Dillingham Igneous Pv 5810 185 KCg3 TA002Gemuk Group -- Permian volcanic rocks Predominantly dark-green to black, altered mafic volcanic rocks having abundant amygdules. Volcanic breccia, calcareous tuff, and pillow lava constitute lower beds, pillow lavas in middle, and phyllitic calcareous tuff and tuffaceous limestone constitutPermian? and Triassic? Taylor MountainsIgneous 5810 1913 Pv TA019Permian volcanic rocks Predominantly dark-green to black, altered mafic volcanic rocks having abundant amygdules. Volcanic breccia, calcareous tuff, and pillow lava constitute lower beds, pillow lavas in middle, and phyllitic calcareous tuff and tuffaceous limestone constitutPermian? and Triassic? Taylor MountainsIgneous 6080 1903 Mrc TA019Rainbow chert Mostly highly deformed white, gray, red, and minor green or black, thin-bedded to massive chert. It is locally banded or brecciated and interbedded with minor red siliceous shale, argillite, dolomitic limestone, greywacke, and rare red volcanic rocks anMississppian? Associated and presumably overlying limestone has yielded Permian megafossils (Hoare and Jones, 1981). One locality on the shore of Chikuminuk Lake yielded Triassic radiolaria, which is yet to be explained Taylor MountainsSedimentary 6412 1905 MzPzgps TA019Greenstone, phyllite, and schist Fine- to coarse-grained greenstone, occasionally calcareous or schistose, rarely interbedded with green chert, argillite and tuff. Gray to black phyllite or slaty argillite, occasionally calcareous or sulfide-bearing along fault zones. Greenschist withMesozoic or Paleozoic Taylor MountainsMetamorphic 6617 200 Sab TA007Algal boundstone Thick to massive bedded, light gray algal boundstone, locally dolomitized; composed primarily of spongiostromate algal heads (including abundant oncoid forms). Equivalent to Sl of Gilbert (1981) Late Silurian (Ludlovian-Pridolian) Aphrosalpingid sponges (notably Aphrosalpinx textilis Miagkova) locally common. Moinr accessory brachiopods Taylor MountainsSedimentary Sab 6617 8200 Sab TA008Algal boundstone Thick to massive bedded, light gray algal boundstone, locally dolomitized; composed primarily of spongiostromate algal heads (including abundant oncoid forms). Equivalent to Sl of Gilbert (1981) Late Silurian (Ludlovian-Pridolian) Aphrosalpingid sponges (notably Aphrosalpinx textilis Miagkova) locally common. Moinr accessory brachiopods Taylor MountainsSedimentary Sab 6617 15667Sab TA015Algal boundstone Thick to massive bedded, light gray algal boundstone, locally dolomitized; composed primarily of spongiostromate algal heads (including abundant oncoid forms). Inferred from air photos Late Silurian (Ludlovian-Pridolian) Aphrosalpingid sponges (notably Aphrosalpinx textilis Miagkova) locally common. Moinr accessory brachiopods Taylor MountainsSedimentary Sab 6620 300 Sls TA007Lime mudstone Thin- to medium-bedded, laminated, dark gray to dark brown, platy lime mudstone, having strong petroliferous odor. Coarse-grained limstone debris-flows having clasts of algal boundstone reef material common in uppermost part of unit; immediately below cLate Silurian (Wenlockian) Graptolites and conodonts Taylor MountainsSedimentary Spf 6620 8300 Sls TA008Lime mudstone Thin- to medium-bedded, laminated, dark gray to dark brown, platy lime mudstone, having strong petroliferous odor. Coarse-grained limstone debris-flows having clasts of algal boundstone reef material common in uppermost part of unit; immediately below cLate Silurian (Wenlockian) Graptolites and conodonts Taylor MountainsSedimentary Spf 7510 400 Olss TA007Tcherskidium-bearing limestone Brown, medium- to thick-bedded skeletal lime packstone to wackestone. Late Ordovician (Ashgillian) Abundant pentameroid brachiopods (Tcherskidium and Proconchidium (or Ecconchidium)) Taylor MountainsSedimentary Olss 7515 450 Os TA007Shale Extremely poorly exposed brown and gray 'chippy' shale, silty shale and silicified limestone Ordovician Taylor MountainsSedimentary Os 7515 451 Ocs TA008Clastic rocks Clastic rocks of middle Ordovician age Middle Ordovician Taylor MountainsSedimentary 7560 500 Oab TA007Algal boundstone and lime mudstone Medium- to thick-bedded, dark-gray to brown algal thrombolites (boundstone) interbedded with light-gray weathering thin- to medium-bedded lime mudstone. Early Ordovician Trilobites Taylor MountainsSedimentary Oab 7560 8500 Oab TA008Algal boundstone and lime mudstone Medium- to thick-bedded, dark-gray to brown algal thrombolites (boundstone) interbedded with light-gray weathering thin- to medium-bedded lime mudstone. Early Ordovician Trilobites Taylor MountainsSedimentary Oab 7570 600 Ols TA007Lime mudstone Thin- to medium-bedded, yellow-gray weathering, dark-gray fresh, burrow mottled lime mudstone. Peloidal mudstone locally common. Early Ordovician Gastropods and conodonts Taylor MountainsSedimentary Ols 8014 8014 Cls TA008Limestone Medium- to thick-bedded, commonly light-gray to dark-gray, rarely pink weathering (light-gray fresh) lime mudstone having locally abundant, well developed wavy styolites. Minor green-gray shale intervals present locally. Cambriam, middle Trilobites locally abundant and diverse in this subunit and are indicative of a Mayan (late Middle Cambrian age Taylor MountainsSedimentary 8015 8015 Cls TA008Limestone and siliclastic rocks Thin-bedded platy limestone associated with coarse-grained siliclastic sandstone and granule comglomerate, possible shale. Cambriam, middle or early Taylor MountainsSedimentary 8340 195 Pal TA002Holitna Group Various types of limestone ranging from dense, fine-textured to more coarsely crystalline (recrystallized) types. Recrystallized facies are partly dolomitic. Massive limestone is predominant and forms prominent topographic features. Thinly bedded variDevonian to Silurian Predominatly stromatoporoids and corals but includes sponges, bryozoans, brachiopods, trilobites, and ostracodes. Taylor MountainsSedimentary DZn 8340 195 DSab TA005Algal boundstone Algal boundstone Early Devonian to Late Silurian Taylor MountainsSedimentary DZn 8340 895 ds TA008Dolostone Dolostone Paleozoic Taylor MountainsSedimentary DZn 8340HFS 896 Pzls TA008Marble Hornfelsed carbonate rocks Paleozoic Taylor MountainsMetamorphic 9120 8420 Zs TA008Dolostone, limestone, orthoquartzite, and minor chert Medium-bedded, medium-gray, orange weathering dolostone, limestone, orthoquartzite, and minor chert. Dolostone has locally abundant floating quartz grains, is locally trough cross-stratified, but also has well developed parallel laminations, low domal sProterozoic None reported Taylor MountainsSedimentary