Da
Ambler sequence, Schist belt
Devonian
Interlayered white- to medium-gray-weathering metarhyolite, dark-green-weathering metabasite, pale-gray-weathering marble, and brown- to dark-gray-weathering calcareous, pelitic and carbonaceous schist exposed in two areas in the Schist belt. The unit oc
Till, A.B., Dumoulin, J.A., Harris, A.G., Moore, T.E., Bleick, Heather, and Siwiec, Benjamin, in press, Bedrock geologic map of the southern Brooks Range, Alaska, and accompanying conodont data:  U.S. Geological Survey Scientific Investigations Map SIM-?
Dg
Granitic orthogneiss
Tan- to gray-weathering, equigranular to porphyroblastic, fine- to coarse-grained metagranitic bodies ranging in size from less than a kilometer to over 20 km across, found in both the Schist and Central belts.  Generally granitic in composition and made
Dhf
Hunt Fork Shale, Central belt and part of Northern thrust assemblages
Late Devonian
Dark-gray to black phyllite and lesser gray-green phyllite with thin layers of siliceous or calcareous metasiltstone, lithic wacke, metasandstone, and minor layers of fossiliferous metalimestone exposed along the length of the northern boundary of the ma
Dhf*
Hunt Fork Shale, strongly foliated, Central belt and part of Northern thrust assemblages
Dl
Metalimestone, Central belt and part of Northern thrust assemblages
Metalimestone and lesser metasandstone, metasiltstone, phyllite, and minor conglomerate.  Dl includes limestone of Nakolik River (map unit Dnl) of Karl and others (1989b) in the Baird Mountains quadrangle, limestone layers in the Chandalar quadrangle cal
Dmu
Metasedimentary and lesser metaigneous rocks, Central belt and part of Northern thrust assemblages
Middle and Late Devonian
Heterogeneous expanses of calcareous, siliceous, and volcaniclastic metasedimentary rocks, with lesser metaigneous rocks, exposed along the length of the Central belt.  Includes interlayered gray, maroon, purple and green siliceous phyllite, brown and bl
Metasedimentary and lesser metaigneous rocks, volcanic-rock bearing subunit, Central belt and part of Northern thrust assemblages
Parts of the unit containing felsic to intermediate volcanic rocks or sedimentary rocks with abundant volcanic clasts are shown with a vertical line overlay. 
Heterogeneous expanses of calcareous, siliceous, and volcaniclastic metasedimentary rocks, with
Metasedimentary and lesser metaigneous rocks, Central belt and part of Northern thrust assemblages, Ferriginuous and Calcareous schist
Relatively lithologically simple section in the north and northeast Survey Pass quadrangle consisting of light brown, gray, and orange-weathering ferruginous and calcareous mica schist, phyllite, and metasiltstone is shown with a diagonal line overlay.
Dn
Noatak Sandstone, Central belt and part of Northern thrust assemblages
Metasandstone, metasiltstone, and subordinate phyllite exposed in the northern Baird Mountains, Ambler River, and Survey Pass quadrangles; part of Endicott Group (Tailleur and others, 1967). The unit was established by Smith (1913); Dutro (1952) designat
DOb
Baird Group, Central belt and part of Northern thrust assemblages
Devonian to Ordovician
Beige- to orange-weathering, laminated, partly argillaceous to silty metalimestone and light- to dark-gray, flaggy-bedded to massive metalimestone, marble, and dolostone. DOb is part of the Nakolik River sequence of Karl and others (1989b). The Baird Gro
DOc
Younger carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblages
Middle Devonian to Ordovician
Very light- to dark-gray- (locally orange-) weathering, gray to black, commonly massive dolostone and lesser metalimestone and marble exposed in the Nanielik antiform (northeastern Baird Mountains and northwestern Ambler River quadrangles) and in the nor
DpCgn
Schist and paragneiss, Arrigetch-Igikpak thermal high
Devonian to Proterozoic?
Pelitic schist, metaquartzite, mafic schist and other lithologies; gneissic textures are particularly common where the unit is adjacent to metaplutonic rocks.  Mafic rocks within the unit contain assemblages stable in the albite-epidote-amphibolite facie
DpCm
Metamorphic rocks, Mosquito terrane
Pelitic schist, metabasite, minor felsic orthogneiss and meta-ultramafic rock exposed in two small areas along the Kobuk fault zone in the northeastern Bettles and southwestern Chandalar quadrangles.  The rocks exhibit amphibolite-facies metamorphic asse
DpCsc
Calcareous schist, Schist belt
Devonian to Proterozoic
Light-gray-, brown- and locally orange-weathering, lithologically heterogeneous mix of marble and carbonate-rich, quartz-rich, and mafic schist derived from metasedimentary and metaigneous protoliths; one of two major units that extends along the length
Calcareous schist, albite-rich subunit, Schist belt
Calcareous schist - metachert and conglomerate subunit, Schist belt
DpCsm
Schist and marble, undivided, Arrigetch-Igikpak thermal high
Gray marble, orange dolomitic marble, magnetite-bearing chlorite schist, and pelitic schist exposed in the central Survey Pass quadrangle.  Lithologies are interlayered and isoclinally folded, and the unit has a bedded appearance due to layers of resista
Dps
Lithic sandstone and shale, Phyllite belt
Dominantly gray-green lithic sandstone, lesser brown quartz sandstone, and black shale and silty shale exposed in the western Christian quadrangle (Brosg and Reiser, 2000).  Sandstones are fine- to medium-grained and thin- to medium-bedded.  Black shale
Schistose lithic sandstone and shale, Phyllite belt
Schistose varieties are equivalent to units "Dmw" and "Dpm" of Brosg and Reiser (2000).  
Dominantly gray-green lithic sandstone, lesser brown quartz sandstone, and black shale and silty shale exposed in the western Christian quadrangle (Brosg and Reis
DSc
Carbonate rocks of Cosmos Hills, Cosmos Hills sequence
Devonian and Silurian
Thin-bedded to massive dolostone, metalimestone, and marble, locally graphitic or phyllitic, exposed in fault slices in the Cosmos Hills, Shungnak and Ambler River quadrangles. The unit includes minor thin, micaceous layers interpreted as airfall tuffs,
Dsq
Quartz-mica schist, Schist belt
Gray, dark-gray, or brownish-gray weathering, dominantly pelitic or semipelitic schist that constitutes the major lithologic unit of the Schist belt.  Outcrops vary from blocky and resistant (quartz-rich varieties) to platy and less resistant (mica-rich
JCs
Sedimentary rocks, Central belt and part of Northern thrust assemblages
Jurassic to Carboniferous
Sandstone, shale, argillaceous limestone, limestone, dolostone, mudstone, chert and siltstone in north-central Wiseman quadrangle.  The unit conformably overlies the Kanayut Conglomerate (Bowsher and Dutro, 1957) of the Endicott Group (Tailleur and other
JDab
Mafic metavolcanic and metaintrusive rocks, metachert, metalimestone, and amphibolite of the Angayucham terrane, Angayucham Terrane, Serpentinite, And Yukon-Koyukuk Basin
Early Jurassic to Devonian
Metamorphosed pillow basalt, hyaloclastic breccia, basaltic tuff, diabase, microgabbro, radiolarian and tuffaceous chert, minor metalimestone, and rare mafic schist in an imbricate package exposed along the southern boundary of the map area. The package
JDk
Rocks of the Kivivik Creek sequence, Central belt and part of Northern thrust assemblages
Jurassic to Devonian
Consists, in ascending order, of Devonian marine sedimentary rocks equivalent to unit Dmu, sandstone, conglomerate, and shale of the Endicott Group (Devonian and Mississippian), limestone and tuff (Mississippian), chert and phyllite (Carboniferous), and
Kg
Granitic rocks
Cretaceous
Granite, quartz monzonite, and granodiorite of the northern Ruby terrane, exposed along the southern boundary of the Chandalar quadrangle (Brosg and Reiser, 1964).  K-Ar dates range from 103ñ6 to 110ñ6 Ma (Blum and others, 1987)
Khs
Hammond River shear zone, Central belt and part of Northern thrust assemblages
Cretaceous?
Heterogeneous mix of finely laminated, mostly mylonitic lithologies derived in part from adjacent units exposed in the eastern Wiseman and western Chandalar quadrangles.  Unit is recessive, poorly exposed, and includes large (up to 0.5 km across) bodies
KJm
Melange, Phyllite belt
Cretaceous to Jurassic
Tectonic assemblage of meter to kilometer-scale fault slivers of pillow basalt, mafic schist, metagabbro, metalimestone, metachert, metamorphosed lithic sandstone, phyllite, and rare serpentinite exposed in low hills in the south central and southwestern
Km
Migmatite
Intermixed granitic rocks, biotite schist, and hornblende hornfels; pyroxene hornfels and granitic dikes, associated with Cretaceous granitic rocks.  All exposed in the northern Ruby terrane, along the southern margin of the Chandalar quadrangle (Brosg
Ks
Conglomerate, sandstone, and shale, Angayucham Terrane, Serpentinite, and Yukon-Koyukuk Basin
Conglomerate and finer grained sedimentary rocks exposed along the southern map boundary. The unit varies in character from massive, poorly stratified rocks rich in mafic intrusive and extrusive clasts at the base of the unit to well-sorted sedimentary r
Kvg
Volcanic lithic sandstone and mudstone, Angayucham Terrane, Serpentinite, and Yukon-Koyukuk Basin
Fine-grained to conglomeratic sandstone and fine-grained laminated mudstone exposed along the south-central boundary of the map. Mudstone is locally tuffaceous.  Clasts are predominantly intermediate and mafic volcanic and intrusive rocks and chert with
Mc
Quartz-rich conglomerate, Central belt and part of Northern thrust assemblages
Mississippian?
Quartz- , chert-, quartzite-, and slate-clast conglomerate with minor thin layers of metasandstone and phyllite exposed in the Ambler River, Survey Pass, and Wiseman quadrangles.  Quartz and chert clasts are most common; chert clasts are varicolored.  Th
Mcp
Carbonaceous chert and siliceous phyllite, Central belt and part of Northern thrust assemblages
Mississippian
Black carbonaceous metachert and siliceous phyllite exposed in a small area in the northwestern Baird Mountains quadrangle.  Local layers of black carbonaceous metalimestone contain conodonts of Devonian-Mississippian age (Table A-1). The unit likely for
MDe
Endicott Group, undivided, Central belt and part of Northern thrust assemblages
Mississippian and Devonian
Shale and sandstone exposed in the northwest Baird Mountains quadrangle.  Represents undifferentiated parts of the Endicott Group that are equivalent to the Hunt Fork Shale (unit Dhf), the Noatak Sandstone (unit Dn) and the Mississippian Kayak Shale (par
MDer
Eli River sequence, Northern thrust assemblages
Dolostone, limestone, argillaceous or sandy limestone, sandstone, and limestone and dolostone with chert that make up the Eli River sequence of Karl and others (1989b).  MDer consists of unnamed Middle Devonian carbonate rocks (here excluded from the Bai
MDk
Kanuyut Conglomerate, Central belt and part of Northern thrust assemblages
Early Mississippian? and Late Devonian
Quartz conglomerate, quartzite, metasandstone, phyllite, shale, and metalimestone in the Ambler River, Survey Pass, and Wiseman quadrangles.  Includes metasiliciclastic and metacarbonate strata in Ambler River and Survey Pass quadrangles, most with few t
Quartzite, pebbly quartzite, conglomerate, and minor siltstone.  MDk is exposed in a few small areas in the northwestern Baird Mountains quadrangle and the northeastern Ambler River quadrangle, and is widely distributed in northern Survey Pass quadrangle
MDk_101
Mkkl
Kekiktuk Conglomerate(?), Kayak Shale of Endicott Group, and Lisburne Group, Central belt and part of Northern thrust assemblages
Quartzite, conglomerate, phyllite, metalimestone, slate, dolostone, marble, and chert.  The succession occurs in several fault-bounded exposures in the east-central Ambler River quadrangle. Within the fault-bounded exposures, the intensity of deformation
Mkl
Kayak Shale of Endicott Group and Lisburne Group, Central belt and part of Northern thrust assemblages
Phyllite or slate, siltstone, sandstone, limestone, and chert exposed in two small areas in the northwestern Baird Mountains quadrangle and in a larger discontinuous outcrop belt in the northern Survey Pass quadrangle.  In the Baird Mountains quadrangle,
Phyllite or slate, siltstone, sandstone, limestone, and chert exposed in two small areas in the northwestern Baird Mountains quadrangle and in a larger discontinuous outcrop belt in the northern Survey Pass quadrangle.  One exposure in the Baird Mountain
Ml
Carbonate rocks, Central belt and part of Northern thrust assemblages
Light- to medium-gray weathering, dark-gray metalimestone and dolostone with locally abundant layers and lenses of black chert, exposed at one locality in the Nanielik antiform, northeastern Baird Mountains quadrangle.  The unit contains conodonts of Lat
Mu
Metasedimentary rocks, Central belt and part of Northern thrust assemblages
MzDm
Igneous and sedimentary rocks of the Maiyumerak Mountains, Northern thrust assemblages
Mesozoic? to Devonian
Basalt, limestone, and two belts of mlange exposed in the northwesternmost part of the map area.  Four northeast-southwest trending belts defined by Karl and others (1989b) and revised in Karl (1992) include, from east to west: matrix supported mlange
MzPzs
Serpentinite, Angayucham Terrane, Serpentinite and Yukon-Koyukuk Basin
Mesozoic? to Paleozoic?
Greenish-gray, yellowish-green, olive green or greenish-black serpentinite, minor basaltic rocks, harzburgite tectonite, and nephrite jade exposed in the southern Ambler River and adjacent Shungnak quadrangles. In the Cosmos Hills, fault-bounded serpenti
OpCc
Older carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblages
Middle Ordovician to Proterozoic?
Dolostone, metalimestone, marble and subordinate quartzose metasedimentary rocks, carbonate conglomerate, and metabasite exposed in the in the Nanielik antiform (northeastern Baird Mountains and northwestern Ambler River quadrangles), central Survey Pass
Older carbonate rocks of the Nanielik antiform, Central belt and part of Northern thrust assemblages, Ordovician rocks only
pCam
Metamorphic rocks of Mt. Angayukaqsraq, Central belt and part of Northern thrust assemblages
Proterozoic
Amphibolite, metaquartzite, calcareous schist, metapelite, and a few small bodies of metagranite and metagabbro, exposed in the northeastern Baird Mountains quadrangle around Mt. Angayukaqsraq and in the northeastern Ambler River quadrangle. Lithologies
pCg
Granitic orthogniess
Metagranitic rocks of several Proterozoic ages exposed in southern Baird Mountains and western Wiseman quadrangles.  In the Schist belt in the Baird Mountains quadrangle, a light-gray, medium- to fine-grained, foliated to gneissic metamorphosed granite s
Pzb
Black phyllite and siliceous phyllite, Central belt and part of Northern thrust assemblages
Paleozoic?
Gray to dark-gray carbonaceous phyllite, locally silica rich, exposed in the Central belt in the western Ambler River quadrangle.  Equivalent to parts of Pzbs of Mayfield and Tailleur (1978)
Pzbq
Black quartzite, Schist belt
Black-weathering, fine- to medium-grained black metaquartzite exposed along the contact between units Dsq and DpCsc near the boundary between the Baird Mountains and Ambler River quadrangle.  Locally  may contain small amounts of mica and show segregatio
Pzbs
Black metasedimentary rocks, Central belt and part of Northern thrust assemblages
Paleozoic
Dark-gray to black phyllite and calcareous phyllite with dark-gray to orange-weathering marble and dolostone layers up to 50 m thick are exposed in the northeastern Survey Pass and northwestern Wiseman quadrangles.  In the Wiseman quadrangle, the unit is
Pzj
Metasedimentary rocks of Jesse Mountain, Central belt and part of Northern thrust assemblages
Generally fine grained, phyllitic to schistose, gray-weathering meta-argillite, black-weathering metaquartzite, marble, and brown weathering impure marble, exposed in a single area in the eastern Wiseman and western Chandalar quadrangles.   Carbonate roc
Pzm
Marble, Central belt and part of Northern thrust assemblages
White to gray (less commonly black), fine to coarsely crystalline, massive to platy marble and subordinate metalimestone and dolostone occurs discontinuously in all quadrangles within the map area. Pzm locally contains abundant disseminated quartz or mic
Pzp
Phyllite, Central belt and part of Northern thrust assemblages
Phyllite, fine-grained schist, and phyllonite of the Central belt that underlie areas of poor exposure in the northeastern Baird Mountains quadrangle, western Ambler River quadrangle, and northwestern Chandalar quadrangle.  Locally contains minor lenses
Pzpc
Carbonate rocks of phyllite belt
Fault-bounded blocks of marble, metalimestone, and dolostone that crop out in southwestern Ambler River quadrangle.  Carbonate rocks are locally intercalated with black phyllite, black metaquartzite, and metachert, contain megafossils (corals, brachiopod
PzpCb
Metasedimentary rocks of Bluecloud Mountain, Central belt and part of Northern thrust assemblages
Paleozoic to Proterozoic?
Light-, medium-, and dark-gray phyllite, dark-gray to black metaquartzite, dark-gray and grayish-brown calcareous phyllite,  and reddish-brown-weathering impure marble exposed in fault-bounded lenses along the Schist belt-Central belt contact in the Wise
PzpCbs
Biotite schist, Ruby terrane
Quartz-albite-oligoclase-biotite schist with staurolite and andalusite exposed in the southeastern Chandalar quadrangle, adjacent to rocks of the Schist belt.  Age of metamorphism not known
PzpCcm
Metasedimentary and metavolcanic rocks, undivided, Central belt and part of Northern thrust assemblages
Paleozoic to Proterozoic
Heterogeneous assemblage of interlayered calcareous, mafic, and siliceous rocks exposed in the central Baird Mountains, Ambler River, and Wiseman quadrangles.  Includes black quartzite, meta-argillite, and marble; white quartzite; green, buff, and black
PzpCem
Metamorphic rocks of the Ernie Lake area, Central belt and part of Northern thrust assemblages
Coarse crystalline marble, orange dolomitic marble, quartz-mica schist, metaquartzite, calcareous schist, graphitic metaquartzite, and metabasite exposed in the eastern Survey Pass and western Wiseman quadrangles. Marble is the most common lithology; oth
PzpCg
Pale gray-green, massive to gneissic granitic to dioritic orthogneiss exposed in the Schist belt in the southern Baird Mountains quadrangle.  This body was one of several metagranitic rocks from the Schist belt analyzed to evaluate the temperature and pr
PzpCm
Mafic schist, Central belt and part of Northern thrust assemblages
Paleozoic? to Proterozoic?
Dark green-weathering foliated mafic schist exposed in one area on the boundary between the Ambler River and Survey Pass quadrangles. Composed of green to blue-green amphibole, albite, epidote, quartz, and biotite.  Grain size is variable.  Epidote occur
PzpCqs
Quartz-rich metasedimentary rocks, Central belt and part of Northern thrust assemblages
Relatively homogeneous assemblage dominated by light greenish-gray fine-grained schist, typically accompanied by minor layers of metaconglomerate, marble, and calcareous schist.  Exposed in the southern Central belt in the western Survey Pass quadrangle
PzpCsr
Ruby schist, Ruby terrane
Biotite-bearing pelitic schist with subordinate metaquartzite, exposed in the southern Chandalar quadrangle. May have crystallized at upper greenschist or amphibolite facies (Dusel-Bacon and others, 1989).  Equivalent to schists of the Ruby geanticline,
Pzpg
Phyllite and graywacke, Phyllite belt
Dark-gray to black phyllite and brown-weathering lithic sandstone, sandstone, and mudstone are exposed along the southern boundary of the schist belt.  The unit varies in breadth along strike.  In the Wiseman and Chandalar quadrangles, two subunits are r
Pzsg
Mafic schist, Schist belt
Green and greenish-gray, schistose to massive, irregularly-shaped bodies and lenses of metamorphosed mafic rocks in units Dsq and DpCsc large enough to show at the scale of the map occur in the Survey Pass and Chandalar quadrangles. Relict pillow structu
Pzsm
Marble of the Schist belt
Metacarbonate rocks form an elongate belt in the central Ambler River quadrangle and are the only mappable occurrence of massive carbonate strata in the Schist belt. The unit surrounds the Redstone pluton (Sheet 2) and includes a variety of rock types (J
Pzw
Weakly to moderately metamorphosed metasandstone, meta-argillite, phyllite, conglomerate, and rare marble exposed in two belts that straddle the northern part of the Wiseman/Chandalar quadangle boundary.  The northern belt is composed of metasandstone an
Pzw_572
Qs
Surficial sedimentary deposits, undivided
Quaternary
Frost-rived rubble on slopes and broad low ridges; glacially deposited sand, gravel, and boulders; fluvial gravel and sand; terrace deposits; wetlands
QTb
Basalt
Quaternary? or Tertiary?
Flat-lying, vesicular  olivine basalt flows exposed in the southeastern part of the Chandalar quadrangle. Thought to be about 300 meters thick (Brosg and Reiser, 1964)
SCvs
Volcanic and sedimentary rocks, Doonerak antiform
Silurian to Cambrian
Volcanic rocks, volcaniclastic rocks, and clastic sedimentary rocks exposed in the core of the Doonerak antiform, northeastern Wiseman quadrangle.  The unit can be divided into at least two lithologic sequences, one dominated by volcanic rocks, the other
Spl
Black phyllite and metalimestone, Central belt and part of Northern thrust assemblages
Silurian
Black siliceous phyllite and metalimestone, metasandstone, metasiltstone, phyllite, and graphitic calcareous schist in the eastern Ambler River and western Survey Pass quadrangles.  Conodonts and graptolites indicate Silurian ages for these strata in the
TrCs
Sedimentary rocks, Doonerak antiform
Triassic to Carboniferous
Quartzite, phyllite, siltstone, conglomerate, shale, sandstone, limestone, argillaceous limestone, dolomitic limestone, and cherty dolostone.  The unit occurs in the Mount Doonerak area in northeastern Wiseman and northwestern Chandalar quadrangles, wher