Qs
Surficial sedimentary deposits, undivided
Quaternary
Frost-rived rubble on slopes and broad low ridges; glacially deposted sand, gravel, and boulders; fluvial gravel and sand; terrace deposits.
AR004
Ambler River
Sedimentary
Ks
Conglomerate, sandstone, and shale
Cretaceous
Conglomerate and finer grained sedimentary rocks that grade from massive, poorly stratified rocks rich in mafic intrusive and extrusive clasts at the base of the unit to a well-sorted sedimentary rock rich in quartz and metagraywacke clasts at the top of
Sparse plant fossils of Early to Late Cretaceous age; Early Cretaceous? marine mollusks
MzPzs
Serpentinite
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 serpentin
Metamorphic
JDab
Mafic metavolcanic and metaintrusive rocks, metachert, metalimestone, and amphibolite of the Angayucham terrane
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. Commonly, me
Radiolarians, conodonts, megafossils, foraminifers, bryozoans, brachiopods
KJm
Melange
Cretaceous to Jurassic
Tectonic assemblage of meter to kilometer-scale fault slivers of pillow basalt, mafic schist, metagabbro, metalimestone, metachert, metagraywacke, phyllite, and rare serpentinite exposed in low hills in the south central and southwestern part of the map
Radiolarians, conodonts
DSc
Carbonate rocks of Cosmos Hills
Devonian and Silurian
Thin-bedded to massive dolostone, metalimestone, and marble, locally graphitic or phyllitic exposed in fault slices in the Cosmos Hills. Minor thin, micaceous layers interpreted as airfall tuffs, and some buff to reddish gray dolostones thought to be of
Conodonts, brachiopods, gastropods, crinoids, tabulate and rugose corals, stromatoporoids
Pzp
Phyllite
Paleozoic?
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
Pzpg
Phyllite and graywacke
Dark gray to black phyllite and brown-weathering greywacke, sandstone, and mudstone 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 recognized:
Pzpc
Carbonate rocks of Phyllite belt
Paleozoic
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
Corals, brachiopods, crinoid debris, conodonts
Mkkl
Kekiktuk Conglomerate(?), Kayak Shale of Endicott Group and Lisburne Group
Mississippian
Quartzite, conglomerate, phyllite, metalimestone, slate, dolostone, marble and chert.  Succession occurs in several fault-bounded exposures in the east-central Ambler River quadrangle.
Echinoderm debris, brachiopods, mollusks, cephalopods, and plant fragments
Mc
Quartz-rich conglomerate
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
Mu
Metasedimentary rocks, undivided
Quartz conglomerate, quartzite, metasandstone, phyllite, shale, and metalimestone in the Ambler River, Survey Pass, and Wiseman quadrangles.
Crinoids, brachiopods, corals, foraminifers, gastropods, molluscan and echinoderm debris, possible bryozoan, pelecypod, brachiopod, ostracode fragments, foraminifers
Spl
Black phyllite and metalimestone
Silurian
Black siliceous phyllite and metalimestone, metasandstone, metasiltstone, phyllite, and graphitic calcareous schist in the eastern Ambler River and western Survey Pass quandrangles.  This unit is part of the Central belt.  Mapped as units Dbl and Db by M
Conodonts, graptolites, radiolarians; corals, gastropods, bryozoans, brachiopods, conularids, and orthocone cephalopods
Dn
Noatak Sandstone
Devonian
Consists of metasandstone and metasiltstone with subordinate interlayers of green, gray, and maroon phyllite and local ironstone concretions. Semischistose textures and minerals indicative of lower greenschist facies metamorphism occur locally, but origi
Late Devonian (some Famennian)conodonts, brachiopods, echinoderms, gastropods, pelecypods, plant debris, and trace fossils
MDk
Kanuyut Conglomerate
Lower Mississippian? and Upper Devonian
Quartzite, pebbly quartzite, conglomerte, and minor siltstone.  Exposed in a few small areas of northwestern Baird Mountains quadrangle, northeastern Ambler River quadrangle, and widely distributed in northern Survey Pass quadrangle. Semischistose and my
Dhf
Hunt Fork Shale
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
Brachiopods (late Frasnian to early Fammenian), mollusks, echinoderms; Middle to Late Devonian conodonts;
Dmu
Metasedimentary and lesser metaigneous rocks
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 significant expanses of rocks mapped as Beaucoup Formation by some workers. T
Megafossils and conodonts are Middle and early Late Devonian
U-Pb zircon crystallization age of 393+/-2 Ma from subunit that contains felsic to intermediate volcanic rocks
Dmu_542
Metasedimentary and lesser metaigneous rocks, calcareous, iron-rich components
Part of heterogeneous expanses of calcareous, siliceous, and volcaniclastic metasedimentary rocks, with lesser metaigneous rocks, exposed along the length of the Central belt.  This part of the unit contains a light brown, gray, and orange-weathering fer
Dmu_541
Metasedimentary and lesser metaigneous rocks, volcanic-rock bearing subunit
Part of heterogeneous expanses of calcareous, siliceous, and volcaniclastic metasedimentary rocks, with lesser metaigneous rocks, exposed along the length of the Central belt, thought to be correlative with the Beaucoup Formation.   This subunit  contain
U-Pb zircon crystallization age of 393+/-2 Ma from a foliated felsic rock
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 northeastern Baird Mountains quadrangle in the Nanielik antiform and in the northwestern Chandalar quadra
Conodonts, corals, stromatoporoids
Pzm
Marble
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.  This unit is part of the Central belt.
Conodonts, silicified two-hole crinoid columnals of late Early-early Middle Devonian  (late Emsian-Eifelian) age; brachiopods; possible stromatoporoids; pelmatozoan; trilobites
Pzsg
Mafic schist
Green and greenish-gray schistose to massive irregularly-shaped bodies and lenses of mafic rocks in units Dsq and DPsc large enough to show at the scale of the map occur in the Survey Pass and Chandalar quadrangles.  This unit is part of the Schist belt.
Pzsm
Marble of the Schist belt
Metacarbonate rocks that form an elongate belt in the central Ambler River quadrangle and are the only mappable occurrence of carbonate strata in the Schist belt. Unit surrounds the Redstone pluton and includes a variety of rock types. White, gray, and b
Conodonts, corals, stromatoporoids, spines, and echinoderm debris
Dhf_101
Hunt Fork Shale - foliated exposures
Pzb
Black phyllite and siliceous phyllite
Gray to dark gray carbonaceous phyllite, locally silica rich, exposed in the Central belt in the western Ambler River quadrangle.  This unit is part of the Central belt.
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 kms across, found in both the Schist and Central belts.  Generally granitic in composition and made
U-Pb zircon dates for orthogneiss 390-396 Ma; 375-395 Ma for orthogneiss at Mt. Igikpak
Da
Ambler sequence
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. "Metarhyolite
One conodont of Devonian age
U-Pb zircon ages from metarhyolite layers 378-386 Ma, bimodal igneous zircon population about 378 and 405 Ma from Arctic deposit.
OPc
Older carbonate rocks of the Central belt
Middle Ordovician to Proterozoic?
Dolostone, metalimestone, marble and subordinate quartzose metasedimentary rocks, carbonate conglomerate, and metabasite exposed in the northeastern Baird Mountains quadrangle, central Survey Pass quadrangle, and along the Dalton Highway in the Wiseman a
Conodonts, stromatolites, protoconodonts, chancellorid sclerites, hyolithids, and steinkerns of monoplacophoran mollusks, acrotretid brachiopods,agnostid arthropods, graptolites
Pzbq
Black quartzite
Black weathering, fine to medium grained black metaquartzite exposed in the western Schist belt along the contact between units Dsq and DPsc.   May contain small amounts of mica and show segregation of quartz and graphite in layers parallel to foliation.
Dsq
Quartz-mica schist
Gray, dark gray, or brownish-gray weathering, dominantly pelitic or semipelitic schist that constitutes a major unit along the length of the Schist belt.  Outcrops vary from blocky and resistant (quartz-rich varieties) to platy and less resistant (mica-r
Youngest detrital zircon population at one locality 370-360 Ma
PzZqs
Quartz-rich metasedimentary rocks
Paleozoic to Proterozoic?
Relatively homogeneous assemblage dominated by light greenish-gray fine-grained quartz-rich schist, typically accompanied by minor layers of metaconglomerate, marble, and calcareous schist.  Exposed in the southern Central belt in the western Survey Pass
Conodont
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 of
Ghosts of radiolarians, sponge spicules, bivalves, fine graphite laminae, stromatolites, conodonts
DpCsc_541
Calcareous schist - albite-rich subunit, Schist belt
PzZcm
Metasedimentary and metavolcanic rocks, undivided
Paleozoic and Proterozoic?
Heterogeneous assemblage of interlayered calcareous, mafic, and siliceous rocks exposed in the central Baird Mountains, Ambler River, and Wiseman quadrangles.  This unit is part of the Central belt.
Conodonts
PzZm
Proterozoic? to Paleozoic?
Dark green weathering foliated mafic schist exposed in one area on the boundary between the Ambler River and Survey Pass quadrangles. This unit is part of the Central belt.
pCam
Metamorphic rocks of Mt. Angayukaqsraq
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, in the south central Baird Mountains quadrangle near the Kob
40Ar/39Ar  - 680 Ma metamorphic age, overprinting event - 40Ar/39Ar age of 120 Ma
pCam_572
Metamorphic rocks of Mt. Angayukaqsraq, remetamorphosed
Amphibolite, metaquartzite, calcareous schist, metapelite, and a few small bodies of metagranite and metagabbro, originally metamorphosed at amphibolite-facies rocks and overprinted by an albite epidote amphibolite facies event.  Mafic outcrops in these
BM004
Baird Mountains
MzDm
Igneous and sedimentary rocks of the Maiyumerak Mountains
Cretaceous? to Devonian
Basalt, limestone, and two belts of melange exposed in the northwesternmost part of the map area.  This unit is part of the Maiyumerak sequence.
Conodonts and megafossils
Tectonite
JDk
Rocks of the Kivivik Creek sequence
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
Conodonts, brachiopods and mollusks, foraminifers; radiolarian ghosts
Mcp
Carbonaceous chert and siliceous phyllite
Black carbonaceous metachert and siliceous phyllite exposed in a small area in the northwestern Baird Mountains quadrangle. Massive iron sulfide intervals with elevated silver and other metal values have been documented.
conodonts, Devonian-Mississippian
MDe
Endicott Group, undivided
Mississippian and Devonian
Shale and sandstone exposed in the northwest Baird Mountains quadrangle.  Represents undifferentiated parts equivalent the Hunt Fork Shale (unit Dhf), the Noatak Sandstone (unit Dn) and the Mississippian Kayak Shale (part of unit Mkl).
Ml
Carbonate rocks
Light- to medium-gray weathering, dark-gray metalimestone and dolostone with locally abundant layers and lenses of black chert; megafossils (mainly silicified) include corals and possible stromatolites exposed at one locality in the Nanielik antiform, no
Corals, stromatolites, conodonts (latest Meramecian to early Chesterian), Meramecian-early Chesterian lithostrotionid corals
Mkl
Kayak Shale of Endicott Group and Lisburne Group
Phyllite or slate, siltsone, sandstone, limestone, and chert in two small exposures in the northwestern Baird Mountains quadrangle and in a larger area in the Survey Pass quadrangle.
Ostracodes, brachiopods, bryozoans, and echinoderm debris, conodonts, crinoid, bryozoan, and coralline debris, brachiopods, gastropods, sponge spicules, endothyrid foraminifers
Brachiopods (late Frasnian to early Fammenian), mollusks, echinoderms; Middle to Late Devonian conodonts
Dl
Metalimestone
Metalimestone and lesser metasandstone, metasiltstone, phyllite, and minor conglomerate.  Assigned in part to Beaucoup Formation by some workers. This unit is part of the Central belt.
late Middle to early Late Devonian conodonts and megafossils (solitary and colonial corals, stromatoporoids, brachiopods, and mollusks)
DOb
Baird Group
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.  The unit hosts several mineral occurrences and metabasaltic rocks of unknown age t
conodonts; corals and stromatoporoids
MDer
Eli River sequence
Dolostone, limestone, argillaceous or sandy limestone, sandstone, and limestone and dolostone with chert. This unit is part of the Eli River sequence defined by Karl and others, 1989).
Stromatoporoids, brachiopods; pelmatozoan, bryozoan, and coral fragments, foraminifers, and algae (possibly mid-Famennian); spiculitic limestone; conodonts
OpCc_541
Older carbonate rocks of the Central belt, restricted
Dolostone, metalimestone, marble and subordinate quartzose metasedimentary rocks, carbonate conglomerate, and metabasite.  Only exposures that contain the Ordovician part of unit OPc are included in this unit.
PzZg
Granitic rocks
Pale gray-green, massive to gneissic granitic to dioritic orthogneiss exposed in the Schist belt in the southern Baird Mountains quadrangle. No direct age control; may be correlative with Pg.
pCg
Metagranitic rocks of several Proterozoic ages exposed in southern Baird Mountains and western Wiseman quadrangles.
U-Pb zircon ages: southern Baird Mtns quad - 705+/-35 Ma; Ernie Lake pluton  - 971+/-5 Ma; Mt. Angayukaqsraq - 750 +/- 6 Ma
BT005
Bettles
Kvg
Volcanic-clast graywacke and mudstone
Fine grained to conglomeratic greywacke 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
Marine mollusks of Late Early Cretaceous (Albian) age
Kg
Granite, quartz monzonite, and granodiorite of the northern Ruby terrane, exposed along the southern boundary of the Chandalar quadrangle.
K-Ar dates from south of map area are 96-112 Ma
Igneous
DpCm
Metamorphic rocks, Mosquito terrane
Devonian to Proterozoic?
Pelitic schist, metabasite, minor felsic orthogneiss and meta-ultramafic rock exposed in two small areas along the Kobuk fault zone in the northeast Bettles and southwest Chandalar quadrangles.  The rocks exhibit amphibolite-facies metamorphic assemblage
54.8 +/- 1.3 Ma white mica cooling age
CH004
Chandalar
QTb
Basalt
Quaternary? or Tertiary?
Flat-lying, vesicular  olivine basalt flows exposed in the southeast part of the Chandalar quadrangle. Thought to be about 300 meters thick.
Km
Migmatite
Intercalated 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.   Inc
Khs
Rocks of the Hammond River shear zone
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
TrCs
Sedimentary rocks
Triassic to Carboniferous
Quartzite, phyllite, siltstone, conglomerate, shale, sandstone, limestone, argillaceous limestone, dolomitic limestone, and cherty dolostone.  Occurs in the Mount Doonerak area in northeastern Wiseman and northwestern Chandalar quadrangles, where it is i
Conodonts; foraminifers; crinoidal packstone; burrows and trace fossils; brachiopods Wolfcampian age
SCvs
Volcanic and sedimentary rocks
Silurian to Cambrian
Volcanic rocks, volcaniclastic rocks, and clastic sedimentary rocks exposed in the core of the Doonerak antiform, northeast Wiseman quadrangle.  The unit can be divided into at least two lithologic sequences, one dominated by volcanic rocks, the other by
Microfossils, brachiopods, trilobites, graptolites, conodonts
K-Ar and Ar-Ar ages of dikes 373-388 Ma and 478 Ma
Pzj
Metasedimentary rocks of Jesse Mountain
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 quadrangle.   This unit is part of the Central bel
Conodonts; brachiopods; coral fragments
Pzw
Metasedimentary rocks
Weakly metamorphosed metasandstone, meta-argillite, phyllite, conglomerate, and rare marble exposed in two belts on the Wiseman/Chandalar quadangle boundary.  This subunit, the northern belt, is composed of metasandstone and argillite, and contains abund
Detrital white mica -Ordovician 40Ar/39Ar cooling age
Pzw_572
Weakly metamorphosed metasandstone, meta-argillite, phyllite, conglomerate, and rare marble exposed in two belts on the Wiseman/Chandalar quadangle boundary.   This subunit, the southern of the two belts, is composed of phyllite, metasandstone with volca
Conodonts, bryozoans, corals
Dps_101
Wacke and lesser amounts of shale - schistose
Schistose varieties of gray-green lithic wacke, lesser brown quartz wacke, and black shale and silty shale exposed in the eastern map area. This unit is part of the Phyllite belt.
OpCc
PzZbs
Biotite schist
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. This unit is part of the Ruby terrane.
DpCsc_101
Calcareous schist - metachert and conglomerate subunit, Schist belt
PzZsr
Ruby schist
Biotite-bearing pelitic schist with subordinate metaquartzite, exposed in the southern Wiseman quadrangle.  Equivalent to schists of the Ruby geanticline, south of the map area, where the earliest documented metamorphic event to affect the schists was bl
CS004
Christian
Dps
Wacke and lesser amounts of shale
Dominantly gray-green lithic wacke, lesser brown quartz wacke, and black shale and silty shale exposed in the eastern map area. Wackes are fine- to medium-grained and thin to  medium-bedded.  Black shale forms up to 50 percent of the unit and occurs in l
HU004
Hughes
SE005
Selawik
SH005
Shungnak
SP004
Survey Pass
Pzbs
Black metasedimentary rocks
Dark gray to black phyllite and calcareous phyllite with dark gray to orange-weathering marble and dolostone layers up to 50 m thick, exposed in the northeastern Survey Pass and northwestern Wiseman quadrangles.   This unit is part of the Central belt.
Brachiopods  - Middle Devonian or Frasnian (early Late Devonian)
Black siliceous phyllite and metalimestone, metasandstone, metasiltstone, phyllite, and graphitic calcareous schist in the eastern Ambler River and western Survey Pass quandrangles.  This unit is part of the Central belt.  Originally mapped as the wester
MDk_101
Kanuyut Conglomerate and Noatak Sandstone
Quartzite, pebbly quartzite, conglomerate, and minor siltstone. This unit includes exposures where Kanayut has not been differentiated from Noatak Sandstone.
Amber sequence
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.  Adjacent to the Arrigetch pluton, the unit contains calc-silicate skarn.  Mineral assemblages from most of the uni
DpCgn
Schist and paragneiss
Pelitic schist, metaquartzite, mafic schist and other lithologies;  gneissic textures are more common where the unit is adjacent to metaplutonic rocks.  Mafic rocks within the unit contain assemblages stable in the albite-epidote-amphibolite facies; expo
PzZb
Metasedimentary rocks of Bluecloud Mountain
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 Wiseman
PzZem
Metamorphic rocks of the Ernie Lake area
Paleozoic to Proterozoic
Coarse crystalline marble, orange dolomitic marble, quartz-mica schist, metaquartzite, calcareous schist, graphitic metaquartzite, and metabasite exposed in eastern Survey Pass and western Wiseman quadrangles. Locally gneissic. This unit is part of the C
Protolith intruded by 971 Ma granitic rock
WI007
Wiseman
Granite, quartz monzonite, and granodiorite of the northern Ruby terrane, exposed along the southern boundary of the Chandalar quadrangle.  Includes one large polygon south-southwest of Caro mapped by Brosge and Reiser as part of their unit MzPzg; remain
JCs
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 of the Endicott Group. Consists of Kayak Shale of the Endicott Grou
Foraminifers; cephalopods, sponge spicules, and radiolarians; burrows and grazing traces
Brachiopods Middle Devonian or Frasnian (early Late Devonian)