nsaclass,label,name,age,description,sources
    "99","bu","Bedrock of unknown type or age","","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.  Also includes rubble of metasiltstone and chert in the Kantishna River quadrangle and other areas of unknown bedrock ","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "100","Qua","Surficial deposits, undifferentiated","Quaternary","Chiefly silt and very fine sand including thick deposits of micaeous silt in the Koyukuk Flats and Nowitna and Innoko Lowlands.  Local deposits of alluvial fan and glacial outwash gravels","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "105","Qf","Floodplain and tidal flats deposits","Holocene","Gravel, sand, silt, and peat. Floodplain deposits in Koyukuk Flats and along Yukon River composed mainly of light gray micaceous silt","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "107","Qua","Surficial deposits, undifferentiated","Quaternary","Chiefly silt and very fine sand including thick deposits of micaeous silt in the Koyukuk Flats and Nowitna and Innoko Lowlands.  Local deposits of alluvial fan and glacial outwash gravels","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "108","Qua","Surficial deposits, undifferentiated","Quaternary","Chiefly silt and very fine sand including thick deposits of micaeous silt in the Koyukuk Flats and Nowitna and Innoko Lowlands.  Local deposits of alluvial fan and glacial outwash gravels","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "110","Qua","Surficial deposits, undifferentiated","Quaternary","Chiefly silt and very fine sand including thick deposits of micaeous silt in the Koyukuk Flats and Nowitna and Innoko Lowlands.  Local deposits of alluvial fan and glacial outwash gravels","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "111","Qf","Floodplain and tidal flats deposits","Holocene","Gravel, sand, silt, and peat. Floodplain deposits in Koyukuk Flats and along Yukon River composed mainly of light gray micaceous silt","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "116","Qf","Floodplain and tidal flats deposits","Holocene","Gravel, sand, silt, and peat. Floodplain deposits in Koyukuk Flats and along Yukon River composed mainly of light gray micaceous silt","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "119","Qsa","Actively drifting and recently stabilized dune fields","Holocene","Fine- to coarse-grained sand.  Great Kobuk and Little Kobuk Sand Dunes in the southwestern Ambler River and southeastern Baird Mountains quadrangles, and Nogahabara Sand Dunes in the Kateel River quadrangle.   The Great Kobuk and Little Kobuk dune fields covering  24 square miles (65 square kilometers)  and 3 square miles (8 square kilometers), respectively, are composed of parabolic or U-shaped dunes and large transverse dune ridges that locally develop into barchan-like dunes.  Wind direction varies from NE to SE.   The Nogahabara  Sand Dunes are  characterized by  a circular field  5 miles (8 kilometer) in diameter consisting  of transverse dunes that migrate outward in wavelike fashion from a deflationary area in the central and western part of the field.  The main field is surrounded by smaller circular and elliptical fields of wavelike transverse dunes that have been recently stabilized or partially stabilized by a thin cover of vegetation","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "120","Qs","Eolian and water-laid sand and silt sheets and stabilized dune fields","Holocene and Pleistocene","Sand and coarse silt.  1)  Baird Mountains, Ambler River, Selawik,  and  Shungnak quadrangles:  Modified and partly dissected sheets of mixed wind-blown and water-laid deposits bordering the south edge of the Brooks Range; 2)  Kateel River and Melozitna quadrangles:  Sheet-like dune fields of wind-blown sand mantling alluvial silt deposits of the Koyukuk Flats.  Dunes are much modified and locally dissected by stream erosion.  Orientation of parabolic dunes suggest deposition by prevailing northeast winds.; 3)  Ruby quadrangle: A broad sheet of wind-blown silt and sand that extends over  a wide area in the Nowitna Lowland south of the Yukon River.  The sheet is much modified by stream erosion, but parabolic and longitudinal dune forms can be recognized in aerial photographs and on 1:63.360 scale topographic maps.  The dune forms have a strong NE-SW orientation and suggest deposition by prevailing northeast winds.  Small isolated sand sheets also occur in Bettles, Hughes, and Medfra quadrangles
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "125","QTgl","Glacial and glaciolacustrine deposits","Pleistocene and Pliocene?","Includes unsorted to poorly sorted till, outwash sand and gravel, alluvium, and eolian deposits.  Along the southern edge of the Brooks Range, unit is characterized by little-modified middle and late Pleistocene drift including prominent morainal ridges (shown by hachured lines), ice-contact features, and glaciolacustrine deposits.  Further south, in the Bettles, Hughes, Shungnak. and Selawik quadrangles, the unit is composed of discontinuous areas of highly modified drift of Pliocene? and early Pleistocene age interspersed with alluvium and eolian deposits.  Glacial erratics occur in hilly parts of the central Shungnak and Hughes quadrangles to an elevation of 1,500 feet (600 meters). In the Bettles quadrangle the southern margin of the unit consists chiefly of lacustrine sediments deposited from a large proglacial lake","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "135","QTgl","Glacial and glaciolacustrine deposits","Pleistocene and Pliocene?","Includes unsorted to poorly sorted till, outwash sand and gravel, alluvium, and eolian deposits.  Along the southern edge of the Brooks Range, unit is characterized by little-modified middle and late Pleistocene drift including prominent morainal ridges (shown by hachured lines), ice-contact features, and glaciolacustrine deposits.  Further south, in the Bettles, Hughes, Shungnak. and Selawik quadrangles, the unit is composed of discontinuous areas of highly modified drift of Pliocene? and early Pleistocene age interspersed with alluvium and eolian deposits.  Glacial erratics occur in hilly parts of the central Shungnak and Hughes quadrangles to an elevation of 1,500 feet (600 meters). In the Bettles quadrangle the southern margin of the unit consists chiefly of lacustrine sediments deposited from a large proglacial lake","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "190","QTgl","Glacial and glaciolacustrine deposits","Pleistocene and Pliocene?","Includes unsorted to poorly sorted till, outwash sand and gravel, alluvium, and eolian deposits.  Along the southern edge of the Brooks Range, unit is characterized by little-modified middle and late Pleistocene drift including prominent morainal ridges (shown by hachured lines), ice-contact features, and glaciolacustrine deposits.  Further south, in the Bettles, Hughes, Shungnak. and Selawik quadrangles, the unit is composed of discontinuous areas of highly modified drift of Pliocene? and early Pleistocene age interspersed with alluvium and eolian deposits.  Glacial erratics occur in hilly parts of the central Shungnak and Hughes quadrangles to an elevation of 1,500 feet (600 meters). In the Bettles quadrangle the southern margin of the unit consists chiefly of lacustrine sediments deposited from a large proglacial lake","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "285","QTgr","Quartz gravel deposits","Quaternary or Tertiary","High-level deposits of quartz pebble gravel; overlies basalt flows of unit Tb","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "300","Qab","Alkalic basalt cones and flows","Pleistocene","Unit comprises numerous alkali basalt, basanite, and hawaiite cones, short flows, and maar craters.  Cones and flows have little or no vegetative cover and still preserve some primary flow structures. Locally contains peridotite and pyroxenite xenoliths.  Unit was erupted through and stratigraphically overlies unit QTb","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "305","Qtb","Tholeiitic basalt cones and flows","Holocene? and Pleistocene","Black glassy olivine tholeiitic basalt flows erupted from two small craters. Flows exhibit well-developed pahoehoe crusts and lack vegetative cover.   One K/Ar isotopic determination from this unit gave a cooling age of 0.19 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "350","QTb","Basalt flows","Pleistocene and Pliocene","Includes the Wrangell Lava consisting chiefly of basalt and andesite in the southeastern part of the map area and olivine basalt and vesicular andesite in the northern part of the map area","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "640","Ts","Small deposits of nonmarine conglomerate, sandstone, shale, and coal","Tertiary","Poorly consolidated nonmarine deposits occur in five areas listed below; the first three are located close to the Kaltag Fault. Pollen  samples from these five areas  range in age from Oligocene to Pliocene.:  1)  Unalakleet quadrangle.  Clay shale, lignite, and volcanic ash exposed on Norton Sound coast.; 2)  Norton Bay quadrangle. Small body of coaly mudstone, lignite, poorly consolidated quartz gravel and sandstone exposed on north side of Unalakleet River valley;  3)  Melozitna and Tanana quadrangles.  Sandstone, claystone, conglomerate, and lignite exposed on south bank of Yukon River near the border of the Melozitna and Tanana quadrangles and small outcrops on the north side of the Yukon River in the Tanana quadrangle; 4)  Tanana quadrangle. Sandstone, shale, coal, and lignite exposed on the Tozitna River and its tributaries in central part of Tanana quadrangle;  5)   Selawik quadrangle. Tiny  body of gravel and sand along an E-W fault in southern part of quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1001","Trs","Rhyolitic volcanic and sedimentary rocks","Tertiary?","Rhyolitic volcanic and minor(?) associated sedimentary rocks are mapped in a small area in the Tanana quadrangle (Chapman and others, 1982; Dover, unpublished data, 1997).  Rhyolitic rocks consist of light- to very light-yellow and yellowish-gray to cream and white flows and breccia.  Tuff and probable welded tuff, generally devitrified, are common and similar in color to the lavas.  Sedimentary rocks include minor light- to medium-gray cherty rocks and very light-yellow to tan and light-olive- to medium-gray, generally thin-bedded to laminated siltstone and shale, grading to argillite
  Unit outside of Youkon-Koyukuk basin map area.","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1002","Td","Dacite and rhyolite lava flows, domes, and volcaniclastic rocks","Eocene and Paleocene","Finely banded dacitic and rhyolitic  lava flows, basal breccia, tuffs, obsidian, and hypabyssal domal intrusive bodies. Spatially associated with andesite and basalt unit (Ta) and forms a compositionally continuous suite with unit Ta.  K/Ar  isotopic cooling ages range from 60 to 40 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1004","Tb","Basalt flows","Oligocene","Vesicular and columnar-jointed basalt flows and lahar deposits. Unit yielded a K/Ar cooling age of 32 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1011","Thr","Rhyolite hypabyssal bodies ","Miocene to Paleocene, mostly Early Tertiary or Eocene?)","Fine-grained porphyritic rhyolite composed of phenocrysts of plagioclase rimmed by orthoclase in a groundmass of plagioclase, orthoclase, quartz, and altered mafic minerals.  Unit probably correlates and forms a compositional continuum with a nearby granite stock (unit Tg), which yielded  an isotopic K/Ar cooling age of 56M","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1081","Tad","Andesite and basalt lava flows and volcaniclastic rocks (Ta) and dacite and rhyolite lava flows, domes, and volcaniclastic rocks (Td), undivided","Eocene and Paleocene","Confined to west-central part of Melozitna quadrangle where field data are insufficient to map units Ta and Td separately","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1103","Ta","Andesite and basalt lava flows and volcaniclastic rocks","Eocene and Paleocene","Subaerial, columnar-jointed, andesite and basalt lava flows that locally contain interbedded tuffs, breccias, and agglomerates.  Lava flows composed chiefly of pyroxene andesite and less commonly of hornblende-bearing high-silica andesite, olivine-bearing basaltic andesite, and  basalt.  Upper part of unit locally underlies and is intruded by dacite and rhyolite of unit Td.  K/Ar isotopic cooling ages range from 65 to 52 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1120","Tt","Tuff and tuff breccia","Eocene or Paleocene","Tuff and breccia are composed of abundant lithic fragments of flow-banded rhyolite  and partially welded pumice in a matrix of devitrified glass shards, altered plagioclase, quartz, and mafic minerals.  Unit contains subordinate altered andesite and dacite lava flows.  Unit appears to cut through unit Ta and is intruded by unit T","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1320","Tg","Granite","Eocene or Paleocene","Fine-grained equigranular to sparsely porphyritic granite characterized by plagioclase laths mantled by orthoclase.  One K/Ar isotopic determination from this unit  yielded a cooling age of 56 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1510","TKd","Dacite and rhyolite lava flows, domes, and volcaniclastic and hypabyssal rocks","early Tertiary and Late Cretaceous","Dacite, rhyolite, and trachyandesite lava flows, domes, sills, dikes, and interlayered breccias and tuffs.  Composed of phenocrysts of  plagioclase, quartz, sanidine, and biotite in a groundmass of quartz and feldspar.  Locally in Unalakleet and Medfra quadrangles, tuffs at the base of unit contain interbeds of quartz- chert-pebble conglomerate, sandstone, siltstone, and thin coaly layers with abundant plant fossils","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1600","TKad","Andesite and basalt lava flows and volcaniclastic rocks (TKa) and dacite and rhyolite lava flows, domes, and volcaniclastic and hypabyssal rocks (TKd), undivided","early Tertiary and Late Cretaceous","Andesite and basalt lava flows and volcaniclastic rocks (TKa) and dacite and rhyolite lava flows, domes, and volcaniclastic and hypabyssal rocks (TKd), undivided","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1601","TKi","Shallow intrusive rocks of silicic and intermediate composition","Tertiary and Late Cretaceous","Includes a wide variety of shallow intrusive rocks including rhyolite, dacite, trachyite, and andesite plugs, domes, sills, and dikes and larger more coarsely crystalline bodies of granite, granodiorite, tonalite, and monzonite porphyry","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1602","TKi","Shallow intrusive rocks of silicic and intermediate composition","Tertiary and Late Cretaceous","Includes a wide variety of shallow intrusive rocks including rhyolite, dacite, trachyite, and andesite plugs, domes, sills, and dikes and larger more coarsely crystalline bodies of granite, granodiorite, tonalite, and monzonite porphyry","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1603","TKd","Dacite and rhyolite lava flows, domes, and volcaniclastic and hypabyssal rocks","early Tertiary and Late Cretaceous","Dacite, rhyolite, and trachyandesite lava flows, domes, sills, dikes, and interlayered breccias and tuffs.  Composed of phenocrysts of  plagioclase, quartz, sanidine, and biotite in a groundmass of quartz and feldspar.  Locally in Unalakleet and Medfra quadrangles, tuffs at the base of unit contain interbeds of quartz- chert-pebble conglomerate, sandstone, siltstone, and thin coaly layers with abundant plant fossils.  K/Ar isotopic cooling ages for this unit  range from 71 to 53 Ma.  Palynoflora collected from coaly layers at the base of the unit in the Medfra quadrangle are latest Cretaceous (Campanian or Maastrichtian)  in age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1604","TKvr","Rhyolite and related rocks","Tertiary and/or Cretaceous","Consists of light gray to pink rhyolitic volcanic rocks and minor dacite, including flows, tuff, welded(?) tuff and breccia.  Exposures of this unit include the volcanic rocks of the Big Creek -- Tokatjikh Creek area of the Melozitna quadrangle (mapped as unit TKv by Patton and others, 1978), the northwestern part of the Tanana quadrangle, the Nowitna River and Nixon Fork-Upper Sulukna River areas, and the Sischu Mountains and northeast in the Medfra (Patton and others, 1980), Ruby (Cass, 1959), Mount McKinley (Bela Csejtey, Jr., written commun., 1993), Tanana (Chapman and others, 1982), and Kantishna River quadrangles (Chapman and others, 1975).  Also includes felsic volcanic rocks associated with volcano-plutonic complexes of the Sleetmute quadrangle, as mapped by Miller and others (1989) and rhyolitic tuff and dacite dikes of the Veleska Lake volcanic field of Bundtzen and others (1997a).  Where determined, age ranges between approximately 70 and 50 Ma","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "1605","TKa","Andesite and basalt lava flows and volcaniclastic rocks","early Tertiary and Late Cretaceous","Columnar-jointed andesite, basaltic andesite, and basalt lava flows.  Composed of phenocrysts of plagioclase and pyroxene in a fine-grained  groundmass of plagioclase microlites, granular pyroxene, and dark glass.  K/Ar isotopic cooling ages range from 64 to 54 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1620","TKi","Shallow intrusive rocks of silicic and intermediate composition","Tertiary and Late Cretaceous","Includes a wide variety of shallow intrusive rocks including rhyolite, dacite, trachyite, and andesite plugs, domes, sills, and dikes and larger more coarsely crystalline bodies of granite, granodiorite, tonalite, and monzonite porphyry","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1630","TKvc","Volcano-plutonic complexes","early Tertiary and Cretaceous","Complexes are composed of small, closely-spaced rhyolite, dacite, andesite, granite, granodiorite, tonalite, and monzonite porphyry bodies, which intrude Cretaceous sedimentary deposits of the Yukon-Koyukuk basin.  Intrusive bodies are too small and too numerous to be mapped separately.  Sedimentary  host rocks are altered to an erosion-resistant hornfels.  A felsic hypabyssal body belonging to the complex in the southwestern part of Unalakleet quadrangle yielded a single K/Ar isotopic cooling age of 69 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1641","TKi","Shallow intrusive rocks of silicic and intermediate composition","Tertiary and Late Cretaceous","Includes a wide variety of shallow intrusive rocks including rhyolite, dacite, trachyite, and andesite plugs, domes, sills, and dikes and larger more coarsely crystalline bodies of granite, granodiorite, tonalite, and monzonite porphyry","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1650","TKi","Shallow intrusive rocks of silicic and intermediate composition","Tertiary and Late Cretaceous","Includes a wide variety of shallow intrusive rocks including rhyolite, dacite, trachyite, and andesite plugs, domes, sills, and dikes and larger more coarsely crystalline bodies of granite, granodiorite, tonalite, and monzonite porphyry","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1655","TKg","Granite and granodiorite","early Tertiary and Late Cretaceous","Fine to coarse-grained, equigranular to porphyritic, biotite granite and rarely muscovite-biotite granite.  K/Ar isotopic cooling  ages for this unit range from 71 to 63 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1660","TKm","Monzonite","early Tertiary and Late Cretaceous","Medium- to coarse-grained, equigranular, biotite and hornblende monzonite, quartz monzonite, monzodiorite, and quartz diorite.  Subordinate monzogabbro and gabbro.  K/Ar isotopic cooling  ages from this unit range from 70 to 66 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1680","TDg","Gabbro and diabase","Tertiary? to Devonian?","Fresh to altered gabbroic and diabasic intrusive bodies.  Unit intrudes rocks as old as middle Paleozoic and as young as Cretaceous.  May represent a wide range of ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1815","Kcc","Carbonate-clast conglomerate, sandstone, and shale","Cretaceous","Poorly sorted nonmarine and shallow-water shelf deposits consisting  of carbonate-rich conglomerate (calcirudite), sandstone (calcarenite), and shale (calcilutite).  Unit contains abundant plant debris and thin seams of bituminous coal.  Clast-supported cobble to boulder conglomerate, composed almost entirely of carbonate rocks, grades eastward into trough cross-bedded, medium- to coarse-grained sandstone and pebble conglomerate fan-delta deposits, which in turn grade eastward into cross-bedded, fine- to coarse-grained, inner and outer shelf sandstone and shale.  Chert, volcanic rock, quartz, and schist detritus present in subordinate amounts. Unit derived in large part from Paleozoic carbonate rocks (Pzcs) of the Seward terrane.   Unit contains sparse palynomorphs of Cretaceous(?) age in the Norton Bay quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1820","Kcvg","Carbonate- and volcanic-clast graywacke and mudstone","Cretaceous","Cyclically interbedded fine- to coarse-grained highly calcareous graywacke; hard, fine- to medium-grained, carbonaceous, volcanic graywacke; and dark carbonaceous mudstone.  Graywacke is typically graded and sole-marked. Carbonized plant debris is abundant.  Graywacke/mudstone ratios are generally high. The unit is interpreted to represent middle and outer submarine fan lobe deposits; some locally thick sections of mudstone probably represent basin plain deposits.  Paleocurrents are generally to the northeast.  Unit appears to be transitional between the carbonate-rich deposits of map unit Kcg and the volcanic-rich deposits of map unit Kvg.   Poorly preserved marine mollusks of late Early Cretaceous (?) age are present in this unit in the Selawik quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1821","Kcg","Carbonate-clast graywacke and mudstone","Cretaceous","Fine-grained to gritty graywacke and laminated micaceous mudstone turbidite deposits composed largely of carbonate detritus and lesser amounts of quartz, chert, volcanic rock, and mica clasts.  Contains abundant carbonized plant debris. The mudstone intervals typically display fine, convolute, cross laminations and current rippled partings. Unit grades from a high graywacke/mudstone ratio on the southwest to a low graywacke/mudstone ratio on the northeast; paleocurrent directions are to the northeast. The abundance of detrital carbonate, quartz, and mica fragments suggest that the unit was derived largely from carbonate rocks and schist units (Pzcs and PzZss), of the Seward terrane.  Unit interpreted to represent submarine mid- to outer-fan deposits.  A single collection of palynomorphs from the Norton Bay quadrangle is Cretaceous in age, possibly late Early or early Late Cretaceous (Albian or Cenomanian)
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1822","Kcc","Carbonate-clast conglomerate, sandstone, and shale","Cretaceous","Poorly sorted nonmarine and shallow-water shelf deposits consisting  of carbonate-rich conglomerate (calcirudite), sandstone (calcarenite), and shale (calcilutite).  Unit contains abundant plant debris and thin seams of bituminous coal.  Clast-supported cobble to boulder conglomerate, composed almost entirely of carbonate rocks, grades eastward into trough cross-bedded, medium- to coarse-grained sandstone and pebble conglomerate fan-delta deposits, which in turn grade eastward into cross-bedded, fine- to coarse-grained, inner and outer shelf sandstone and shale.  Chert, volcanic rock, quartz, and schist detritus present in subordinate amounts. Unit derived in large part from Paleozoic carbonate rocks (Pzcs) of the Seward terrane.   Unit contains sparse palynomorphs of Cretaceous(?) age in the Norton Bay quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1823","Kcvg","Carbonate- and volcanic-clast graywacke and mudstone","Cretaceous","Cyclically interbedded fine- to coarse-grained highly calcareous graywacke; hard, fine- to medium-grained, carbonaceous, volcanic graywacke; and dark carbonaceous mudstone.  Graywacke is typically graded and sole-marked. Carbonized plant debris is abundant.  Graywacke/mudstone ratios are generally high. The unit is interpreted to represent middle and outer submarine fan lobe deposits; some locally thick sections of mudstone probably represent basin plain deposits.  Paleocurrents are generally to the northeast.  Unit appears to be transitional between the carbonate-rich deposits of map unit Kcg and the volcanic-rich deposits of map unit Kvg.   Poorly preserved marine mollusks of late Early Cretaceous (?) age are present in this unit in the Selawik quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1905","Ksu","Shale, siltstone, and sandstone, undivided","Cretaceous","Chiefly dark carbonaceous, generally nonfossilferous shale, siltstone and fine-grained sandstone.  Poorly exposed except where altered to a dark slaty hornfels in the vicinity of plutonic and hypabyssal intrusive rocks. Locally includes a limestone-clast conglomerate in the central Medfra quadrangle and several volcaniclastic horizons in the Ophir quadrangle.  Unit probably correlative in part with unit Kss of Late Cretaceous age, but some beds may be as old as late Early Cretaceous
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1906","Ksu","Shale, siltstone, and sandstone, undivided","Cretaceous","Chiefly dark carbonaceous, generally nonfossilferous shale, siltstone and fine-grained sandstone.  Poorly exposed except where altered to a dark slaty hornfels in the vicinity of plutonic and hypabyssal intrusive rocks. Locally includes a limestone-clast conglomerate in the central Medfra quadrangle and several volcaniclastic horizons in the Ophir quadrangle.  Unit probably correlative in part with unit Kss of Late Cretaceous age, but some beds may be as old as late Early Cretaceous
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1907","Ksu","Shale, siltstone, and sandstone, undivided","Cretaceous","Chiefly dark carbonaceous, generally nonfossilferous shale, siltstone and fine-grained sandstone.  Poorly exposed except where altered to a dark slaty hornfels in the vicinity of plutonic and hypabyssal intrusive rocks. Locally includes a limestone-clast conglomerate in the central Medfra quadrangle and several volcaniclastic horizons in the Ophir quadrangle.  Unit probably correlative in part with unit Kss of Late Cretaceous age, but some beds may be as old as late Early Cretaceous
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1940","Kss","Shallow marine sandstone, siltstone, and shale","Late Cretaceous","Fine-to medium-grained, thinly cross-bedded, fossiliferous sandstone and poorly exposed dark siltstone and shale.  Clasts composed of 40 to 45 percent quartz, 45 to 50 percent volcanic and sedimentary  lithic fragments, and  5 to 15 percent feldspar, chiefly plagioclase.  Clasts set in a finely divided calcareous and argillaceous matrix. Unit deposited in a nearshore  marine  environment.   Unit contains abundant early Late Cretaceous (Cenomanian) species of Inoceramus
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1941","Ks","Fluvial and shallow marine sandstone and shale, undivided","Cretaceous","Nonmarine, fluvial, delta-plain deposits that grade downward into marine delta-front deposits. Fluvial deposits are characterized by fine-grained, locally cross-bedded quartzose sandstone interbedded with micaeous shale and siltstone. Near the base, the fluvial beds are composed of fine- to coarse-grained, lenticular, crossbedded, friable sandstone and conglomerate containing pebble- to grit-size clasts of quartz and chert and lesser amounts of mafic intrusive and extrusive rocks, and schist.  Contains bituminous coal seams as much as 3 feet (90 centimeters) in thickness.  Sandstone composed of quartz, chert, metamorphic detritus, and subordinate amounts of volcanic rock fragments.  The quartzose nature of the lithic clasts (including polycrystalline quartz), as well as the relatively high proportions of potassium feldspar and micas suggest a mixed metamorphic and granitic provenance.  These data, when combined with limited paleocurrent data, indicate that the unit prograded westward from a source area in the Ruby terrane bordering the southeastern margin of the Yukon-Koyukuk basin.   Nonmarine fluvial deposits contain abundant fresh- and brackish-water mollusks and well-preserved plant remains of Late Cretaceous (Cenomanian and Turonian?) age.  Shallow marine deposits contain an abundant molluscan fauna of late Early (Albian) and  early Late (Cenomanian) Cretaceous age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1942","Ksu","Shale, siltstone, and sandstone, undivided","Cretaceous","Chiefly dark carbonaceous, generally nonfossilferous shale, siltstone and fine-grained sandstone.  Poorly exposed except where altered to a dark slaty hornfels in the vicinity of plutonic and hypabyssal intrusive rocks. Locally includes a limestone-clast conglomerate in the central Medfra quadrangle and several volcaniclastic horizons in the Ophir quadrangle.  Unit probably correlative in part with unit Kss of Late Cretaceous age, but some beds may be as old as late Early Cretaceous
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1970","Ksu","Shale, siltstone, and sandstone, undivided","Cretaceous","Chiefly dark carbonaceous, generally nonfossilferous shale, siltstone and fine-grained sandstone.  Poorly exposed except where altered to a dark slaty hornfels in the vicinity of plutonic and hypabyssal intrusive rocks. Locally includes a limestone-clast conglomerate in the central Medfra quadrangle and several volcaniclastic horizons in the Ophir quadrangle.  Unit probably correlative in part with unit Kss of Late Cretaceous age, but some beds may be as old as late Early Cretaceous
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1971","Kss","Shallow marine sandstone, siltstone, and shale","Late Cretaceous","Fine-to medium-grained, thinly cross-bedded, fossiliferous sandstone and poorly exposed dark siltstone and shale.  Clasts composed of 40 to 45 percent quartz, 45 to 50 percent volcanic and sedimentary  lithic fragments, and  5 to 15 percent feldspar, chiefly plagioclase.  Clasts set in a finely divided calcareous and argillaceous matrix. Unit deposited in a nearshore  marine  environment.   Unit contains abundant early Late Cretaceous (Cenomanian) species of Inoceramus
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1985","Ksc","Fluvial and shallow marine sandstone and conglomerate","Late Cretaceous","Fine- to coarse-grained, thinly cross-bedded  sandstone and quartz-chert pebble conglomerate interbedded with dark shale and siltstone.  Sandstone clasts composed of as much as 45 percent quartz and chert,  25 to 45 percent metamorphic rock, as much as 15 percent sedimentary rock, and less than 10 percent argillaceous matrix.   Non-diagnostic plant fossils and fresh-water mollusks are present in abundance.  Represents a prograding delta, which grades upward from nearshore marine deposits of unit Kss into subaerial standline, lagoonal, and coastal plain deposits.   Unit stratigraphically overlies unit Kss and  is overlain and intruded by Late Cretaceous and early Tertiary volcano-plutonic complexes  of unit TKvc
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "1990","Kqc","Quartz- and metagraywacke-clast conglomerate, sandstone, and shale","Cretaceous","Composed chiefly of well-sorted and well-rounded clasts of white quartz and/or metagraywacke in a quartzose and micaceous matrix; schist, chert, greenstone, and limestone clasts  occur in subordinate amounts. Conglomerate is interbedded with quartzose, cross-bedded sandstone and carbonaceous and micaceous mudstone.  Contains rare interbeds of ashy tuff.  Plant fossils and thin bituminous coal seams are locally abundant.  Unit composed chiefly of debris eroded from the Arctic Alaska and Ruby terranes.  Grades downward into unit (Kmc)  reflecting the progressive unroofing of the Arctic Alaska  and Ruby terranes beneath the Angayucham-Tozitna terrane.  Unit is regionally metamorposed to stretched-pebble conglomerate, semischist, and phyllite in  northeastern part of the Shungak quadrangle and in adjoining parts of the Ambler River and Hughes quadrangles.  Sparse plant fossil collections from this unit range in age from late Early Cretaceous to Late Cretaceous.  A K/Ar isotopic cooling age of 86 Ma was obtained from interbedded ash-fall tuff in Selawik quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2020","Ks","Fluvial and shallow marine sandstone and shale, undivided","Cretaceous","Nonmarine, fluvial, delta-plain deposits that grade downward into marine delta-front deposits. Fluvial deposits are characterized by fine-grained, locally cross-bedded quartzose sandstone interbedded with micaeous shale and siltstone. Near the base, the fluvial beds are composed of fine- to coarse-grained, lenticular, crossbedded, friable sandstone and conglomerate containing pebble- to grit-size clasts of quartz and chert and lesser amounts of mafic intrusive and extrusive rocks, and schist.  Contains bituminous coal seams as much as 3 feet (90 centimeters) in thickness.  Sandstone composed of quartz, chert, metamorphic detritus, and subordinate amounts of volcanic rock fragments.  The quartzose nature of the lithic clasts (including polycrystalline quartz), as well as the relatively high proportions of potassium feldspar and micas suggest a mixed metamorphic and granitic provenance.  These data, when combined with limited paleocurrent data, indicate that the unit prograded westward from a source area in the Ruby terrane bordering the southeastern margin of the Yukon-Koyukuk basin.   Nonmarine fluvial deposits contain abundant fresh- and brackish-water mollusks and well-preserved plant remains of Late Cretaceous (Cenomanian and Turonian?) age.  Shallow marine deposits contain an abundant molluscan fauna of late Early (Albian) and  early Late (Cenomanian) Cretaceous age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2021","Ks","Fluvial and shallow marine sandstone and shale, undivided","Cretaceous","Nonmarine, fluvial, delta-plain deposits that grade downward into marine delta-front deposits. Fluvial deposits are characterized by fine-grained, locally cross-bedded quartzose sandstone interbedded with micaeous shale and siltstone. Near the base, the fluvial beds are composed of fine- to coarse-grained, lenticular, crossbedded, friable sandstone and conglomerate containing pebble- to grit-size clasts of quartz and chert and lesser amounts of mafic intrusive and extrusive rocks, and schist.  Contains bituminous coal seams as much as 3 feet (90 centimeters) in thickness.  Sandstone composed of quartz, chert, metamorphic detritus, and subordinate amounts of volcanic rock fragments.  The quartzose nature of the lithic clasts (including polycrystalline quartz), as well as the relatively high proportions of potassium feldspar and micas suggest a mixed metamorphic and granitic provenance.  These data, when combined with limited paleocurrent data, indicate that the unit prograded westward from a source area in the Ruby terrane bordering the southeastern margin of the Yukon-Koyukuk basin.   Nonmarine fluvial deposits contain abundant fresh- and brackish-water mollusks and well-preserved plant remains of Late Cretaceous (Cenomanian and Turonian?) age.  Shallow marine deposits contain an abundant molluscan fauna of late Early (Albian) and  early Late (Cenomanian) Cretaceous age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2023","TKic","Complexes of shallow intrusive rocks and altered Cretaceous sedimentary rocks of the Yukon-Koyukuk basin, undivided","early Tertiary and Cretaceous","Complexes are composed of small, closely-spaced rhyolite, dacite, andesite, granite, granodiorite, tonalite, and monzonite porphyry bodies, which intrude Cretaceous sedimentary deposits of the Yukon-Koyukuk basin.  Intrusive bodies are too small and too numerous to be mapped separately.  Sedimentary  host rocks are altered to an erosion-resistant hornfels.  A felsic hypabyssal body belonging to the complex in the southwestern part of Unalakleet quadrangle yielded a single K/Ar isotopic cooling age of 69 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2030","Kmc","Mafic igneous-clast conglomerate, sandstone, and mudstone ","Cretaceous","Consists of massive poorly stratified and poorly sorted conglomerate composed of pebble- to cobble-size clasts in a graywacke and mudstone matrix.  Clasts predominately mafic intrusive and extrusive rocks, varied colored chert, and locally metagraywacke.  Limestone, quartz, and granitic rock clasts present in subordinate amounts. Conglomerate is interbedded with  mafic- and calcareous-clast  graywacke and mudstone.  Unit composed chiefly of debris eroded from the Angayucham-Tozitna terrane .  Unit stratigraphically underlies unit Kqc.   Contains marine mollusks of Early Cretaceous(?) age in the Selawik quadrangle
","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2101","Kms","Marine sandstone and siltstone","Cretaceous","The shallow marine deposits in the lower part of the unit Ks are mapped separately along the Yukon River and in a belt to the west extending from the southern edge of the Norton Bay quadrangle to the western Kateel River quadrangle.  These deposits compose a marine tongue that underlies the fluvial deposits and thickens westward.  On the Yukon River, the marine deposits consist of fine- to coarse-grained, crossbedded, lenticular sandstone grading down into fine-grained sandstone and interbedded dark-gray siltstone and shale.   In the belt to the west, the marine deposits are composed predominantly of siltstone and shale","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2105","Kvgm","Volcanic graywacke and mudstone","Cretaceous, Albian","Chiefly dark-greenish-gray, fine-grained to gritty, poorly sorted turbiditic graywacke composed largely of first- and second-cycle volcanic debris, but locally containing abundant granitic and metamorphic rock debris.  Dark-gray mudstone interbeds.  Graded bedding common.  Contains some intercalated crystal tuff.  Age assignment based on correlation with similar unit in Hughes quadrangle to north of map area (Patton and others, 1978).  Unit stratigraphically underlies Norton Bay and Melozitna sequence sedimentary rocks and is thickest in Lower Yukon sub-basin (Patton and others, 1994a) on west.  Unit interpreted as submarine fan turbidite (W.W. Patton, Jr., oral commun., 1998)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2106","Kvc","Volcanic-clast conglomerate, sandstone, and shale ","Cretaceous","Massive, poorly stratified pebble to boulder conglomerate, interbedded with dark graywacke and dark finely laminated mudstone.  Unit composed of debris flows and alluvial fan deposits.  Consists chiefly of andesitic volcanic rock detritus, but locally includes notable amounts of granitic and fine-grained tuffaceous material. Unit overlies volcanic breccia and agglomerate of unit Kv of the Koyukuk terrane.   Unit stratigaphically overlies unit Kv and underlies unit Kcc.  A granitic clast from conglomerate yielded a K/Ar cooling age of 113 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2115","Kwcf","Wilber Creek flysch","Cretaceous, Albian","Interlayered siltstone, shale, sandstone, and conglomerate originally subdivided into coarse- and fine-grained units (Weber and others, 1992).  Siltstone and sandstone are medium- to medium-dark-gray and greenish-gray, moderately sorted and very fine- to medium-grained.  Conglomerate is dark-olive-gray to medium-dark-gray, iron-stained, polymictic, unsorted, subangular to well-rounded, ranges in grain size from granules to cobbles.  Clasts are of local derivation and consist of quartzite, limestone, mafic and felsic igneous rocks, greenstone, diorite and other intrusive rocks, sandstone, siltstone, phyllite, chert, rare grit, shale rip-ups, and very rare carbonatite.  Beds are typically internally massive, large- to medium-scale, graded and amalgamated, having planar tops and bases.  Local small-scale trough-crossbeds internally fill large-scale troughs and fining upward cycles are common.  Conglomeratic graywacke occurs within lenses in unit.  Minor small-scale scour-fills locally fine upward into ripple-laminated medium-gray to black siltstone, and dark-gray to black shale.  Albian age based on presence of Paragastroplites flexicostatus.  Graywacke rich in volcanic detritus is locally characteristic and may correlate with the Kathul Graywacke in the Charley River quadrangle east of the map area (Dover and Miyaoka, 1988)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2125","Kqs","Quartz-carbonate sandstone","Early Cretaceous","Fine- to coarse-grained  quartz-carbonate sandstone and conglomerate, quartzose limestone, and pebbly mudstone and siltstone.  Sandstone clasts composed chiefly of quartz, carbonate rock, and quartz-mica schist debris.  Unit contains abundant marine mollusks and belemnites of Early Cretaceous (Valanginian, Hauterivian, and Barremian) age.","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2152","Kcs","Offshore calcareous sandstone, siltstone, and shale","Cretaceous","Fine- to coarse-grained, moderately to highly calcareous, turbiditic sandstone interbedded with dark-gray shale and siltstone.  The sandstone occurs in beds 20 to 40 inches (50 to 100 centimeters)  thick grading upward into finely cross-laminated, muscovite-rich siltstone and shale.  The bases of sandstone beds commonly are marked by flute casts, ripple marks and rip-up clasts of underlying shale layers along with grit-size grains of quartz and chert.  The siltstone and fine-grained sandstone generally contain thin layers of finely comminuted, carbonized plant debris.  Calcareous discoidal concretions as much as 8 inches  (20 cm) in diameter are common.  The sandstone typically consists of poorly sorted clasts of quartz, chert, feldspar (chiefly plagioclase), muscovite, and carbonate rocks in a carbonate-rich matrix.  Carbonate composes as much as 50 percent of the sandstone.   Unit contains sparsely distributed ammonites of late Early Cretaceous (Albian) age and is interpreted as a prodelta facies approximately correlative in age with the marine sandstone, siltstone, and shale deltaic deposits of unit Kms
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2170","","Ungalik Conglomerate","","Obsolete map unit",""
    "2180","Kvg","Volcanic-clast  graywacke and mudstone ","Cretaceous","Hard, fine-grained to conglomeratic, locally tuffaceous, graywacke and dark-gray finely laminated mudstone. The graywacke is composed of matrix-supported clasts of intermediate and mafic volcanic and intrusive rocks and chert.  Clasts of quartz and of metamorphic and granitic rocks are present in subordinate amounts.  Some of the graywacke beds are characterized by a distinctly mottled appearance owing to the presence of laumontite, most commonly in fine-grained tuffaceous-rich layers. Metamorphic detritus becomes increasingly abundant in the upper part of the unit. The graywacke beds display a typical ""Bouma"" sequence grading from massive at the base to laminated in the middle to cross laminated at the top.  Mudstone rip-up clasts are common at the base of the graywacke beds.  The unit has a high graywacke to mudstone ratio and is interpreted to represent middle and outer submarine fan deposits.  Marine mollusks of late Early Cretaceous (Albian) age  were identified in this unit in the Bettles, Hughes, and Kateel River quadrangles
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2181","Kvm","Volcanic graywacke and conglomerate","early Late or late Early Cretaceous?)","Poorly sorted, fine- to coarse-grained graywacke, sandstone, grit, and pebble- to cobble conglomerate composed chiefly of volcanic rock and chert detritus in the Medfra and Ophir quadrangles (Patton and others, 1980; Chapman and others, 1985)).  Contains locally abundant large Inoceramus, brachiopods, and worm tubes.  Includes massive volcanic conglomerate mapped as part of unit Kgs of Patton (1966) in the northwesternmost Kateel River quadrangle.  This conglomerate is probably gradational with coarse breccia and agglomerate of unit Kve","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2182","Kgc","Volcanic graywacke and conglomerate","Early Cretaceous?","Poorly sorted fine- to coarse-grained graywacke sandstone, grit, and pebble to cobble conglomerate composed chiefly of volcanic rock and chert detritus. Interbedded dark mudstone.   Unit is tentatively assigned an Early Cretaceous age. It locally contains abundant shell prisms thought to have been derived from large- shelled Early Cretaceous species of Inoceramus
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2210","Krd","Rhyolite, dacite, and trachyte lava flows and volcaniclastic rocks","Late Cretaceous","Rhyolite, dacite, and trachyte flows and crystal and lithic tuffs, felsic ash-fall tuffs, tuffaceous graywacke, and volcanic conglomerate.   One K/Ar isotopic determination from this unit gave a cooling age of 87 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2260","Kvl","Volcanic rocks","Late Cretaceous","Largely dacite, andesite, and basalt and subordinate andesitic to basaltic subvolcanic rocks.  Ranges from flows, including agglomerate, to tuff and also dikes and sills; all are variably hydrothermally(?) altered.  Subvolcanic rocks are chiefly found in the southwestern part of the map area, but are also sparsely distributed in the Healy quadrangle.  In the Iditarod quadrangle these rocks were mapped as part of two units, the Kuskokwim Group and part of the Iditarod Volcanics.  Distinction between unit TKvi of this map, which also includes the Iditarod Volcanics, is on the basis of the contact relation between these rocks and the underlying or interfingering Kuskokwim Group sedimentary rocks.  This map unit consists of those rocks where the interfingering relationship is most apparent","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2320","Ktg","Tuff, volcanic graywacke, and mudstone","Early Cretaceous","Chiefly crystal and lithic tuffs and volcanic graywacke interbedded with laminated mudstone.   Tuffs and graywacke characterized by abundant potassium feldspar crystals and potassium-rich volcanic rocks fragments.  Unit contains rare mafic and intermediate lava flows.  Unit contains dinoflagellates of late Early Cretaceous (Hauterivian,  Barremian, and possibly Aptian) age.  Unit conformably overlies and is transitional into unit Kv
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2330","Kv","Andesite and basalt lava flows and volcaniclastic rocks","Early Cretaceous","Flows of andesite and basalt, interbedded with tuff, tuff breccia, agglomerate, volcanic conglomerate, and volcanic graywacke.   Flows typically  have phenocrysts of  plagioclase and pyroxene set in a matrix of devitrified glass, altered plagioclase microlites, pyroxene, chlorite, and opaque oxides. Rhyolite and dacite flows are present locally.  Tuffs are composed chiefly of  fine-grained basalt and andesite clasts, plagioclase crystals, and mafic minerals in an altered matrix of devitrified glass. In upper part of the unit, the tuffs are highly calcareous and contain abundant shelly debris, including species of Buchia.  Tuffs commonly occur in cyclically repeated sequences that grade upward from coarse tuff breccia and lapilli tuff to very fine-grained cherty tuff  and blue-green radiolarian chert.  Massive agglomerate, breccia and volcanic conglomerate are present locally.   Unit contains abundant marine mollusks of early Early Cretaceous (Berriasian and Valanginian) age.  K/Ar isotopic cooling ages range from 137 to 120 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2335","Kbd","Spilitic basalt and diabase","Early Cretaceous","Fine-grained, amygdaloidal, spilitic pillow basalt flows and medium- to coarse-grained spilitic diabase intrusive rocks.  Contains subordinate andesitic and basaltic tuffs.  	Appears to overlie unit  Kv and to underlie unit Krd
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2336","Kft","Shoshonitic tuffs and lava flows","Early Cretaceous","Lithic tuffs, pillowed andesite flows, diabase, and volcanic conglomerate of shoshonitic composition, characterized chemically  by very high K20, Rb, and Ba contents and low TiO2 content.  Tuffs consists of coarse-grained volcanic rock fragments, crystals of plagioclase and clinopyroxene, and pumice.  Flows consist of plagioclase and clinopyroxene phenocrysts in a groundmass of plagioclase laths and devitrified glass.  The diabase is compositionally similar to the shoshonitic flows but has a diabasic texture. The conglomerate consists  of well-rounded cobbles of shoshonitic andesite porphyry in a tuffaceous matrix. Unit also locally includes fine-grained syenite intrusive rocks composed of 5 to 15 percent coarse-grained phenocrysts of twinned potassium feldspar in a groundmass of potassium feldspar laths and interstitial quartz.  Two K/Ar isotopic analyses from this unit gave cooling ages of 118 and 117 Ma for this unit","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2410","Kgu","Granitic rocks of uncertain affinities","Cretaceous?","Medium to coarse-grained granitic intrusive and hypabyssal rocks","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2420","Kgd","Granodiorite and granite","Late Cretaceous","Generally fine- to medium-grained equigranular, but locally porphyritic, hornblende-biotite granodiorite, and alaskitic biotite granite.   Locally includes tonalite and quartz monzodiorite.  K/Ar isotopic cooling ages range from 89 to 78 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2440","Kmum","Mafic and ultramafic rocks","Cretaceous","Gabbro, diorite, serpentinite, and mafic volcaniclastic rocks.  Ranges from small, structurally bounded, pervasively sheared, discordant bodies of serpentinized ultramafic rocks wholly enclosed in pelitic schist in the Anchorage quadrangle (Winkler (1992) to dikes and lense-like masses of dark-greenish gray, medium- to coarse-grained gabbro and massive, medium-gray, medium-grained diorite, including the gabbro of Mount Moffit of the Mount Hayes quadrangle and a correlative unit of gabbro, diorite, metagabbro, metadiabase, and amphibolite dikes sills and small plutons (units gbm and mgb, Nokleberg and others, 1992a).  Restricted to bands through the central part of the map area in the Tanana and Kantishna River, Anchorage, and the Big Delta and Mount Hayes quadrangles","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2450","Kgd","Granodiorite and granite","Late Cretaceous","Generally fine- to medium-grained equigranular, but locally porphyritic, hornblende-biotite granodiorite, and alaskitic biotite granite.   Locally includes tonalite and quartz monzodiorite.  K/Ar isotopic cooling ages range from 89 to 78 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2460","Ksm","Syenite and monzonite","Late Cretaceous","Consists chiefly of hornblende syenite, biotite-hornblende monzonite, and monzodiorite, and lesser amounts of biotite diorite and biotite quartz monzonite.  One K/Ar isotopic determination yielded a cooling age of 76 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2470","Kg","Granitic rocks","Cretaceous","Largely granitic, but range from tourmaline-bearing granite to diorite.  Intrusions range from dikes and sills, to small and large plutons.  Widely distributed includes granite plutons in the Mount Hayes quadrangle, and quartz monzonite and granodiorite plutons in the Anchorage, Fairbanks, Livengood, Tanana, and Melozitna quadrangles.  Radiometric ages are as old as 120 Ma and as young as 70 to 65 Ma, but typically range between 105 and 90 Ma.  Plutons yielding ages of 110 Ma or greater than are shown with a vertical crosshatch pattern, whereas those yielding ages of 85 Ma or less are shown with a horizontal crosshatch pattern","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2510","Kmum","Mafic and ultramafic rocks","Cretaceous","Gabbro, diorite, serpentinite, and mafic volcaniclastic rocks.  Ranges from small, structurally bounded, pervasively sheared, discordant bodies of serpentinized ultramafic rocks wholly enclosed in pelitic schist in the Anchorage quadrangle (Winkler (1992) to dikes and lense-like masses of dark-greenish gray, medium- to coarse-grained gabbro and massive, medium-gray, medium-grained diorite, including the gabbro of Mount Moffit of the Mount Hayes quadrangle and a correlative unit of gabbro, diorite, metagabbro, metadiabase, and amphibolite dikes sills and small plutons (units gbm and mgb, Nokleberg and others, 1992a).  Restricted to bands through the central part of the map area in the Tanana and Kantishna River, Anchorage, and the Big Delta and Mount Hayes quadrangles","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2515","Kgr","Granite and granodiorite","Early Cretaceous","Unit consists chiefly of biotite and muscovite-biotite granite and granodiorite.  K/Ar isotopic cooling  ages range from 112 to 96 Ma and two U/Pb zircon analyses give crystallization ages of 112 and 109 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2530","Kgr","Granite and granodiorite","Early Cretaceous","Unit consists chiefly of biotite and muscovite-biotite granite and granodiorite.  K/Ar isotopic cooling  ages range from 112 to 96 Ma and two U/Pb zircon analyses give crystallization ages of 112 and 109 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2535","Knsy","Syenite, monzonite, and nepheline syenite; nepheline syenite unit","Early Cretaceous","large bodies of nepheline syenite  and related rocks shown separately on the map","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2545","Ksy","Syenite, monzonite, and nepheline syenite","Early Cretaceous","Unit composed of syenite, monzonite, and subordinate quartz monzonite, monzodiorite, quartz syenite, and nepheline syenite and related mafic alkaline rocks including malignite, ijolite, shonkinite, and pyroxenite.  K/Ar isotopic cooling ages from units  Ksy and Knsy range from 113 to 99 Ma","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "2812","KJwc","Wilber Creek flysch and Wolverine quartzite, undivided","Early Cretaceous or Late Jurassic","Locally mapped unit consisting of units KJwc and Kwcf in the Tanana quadrangle","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2815","KJw","Wolverine quartzite","Early Cretaceous or Late Jurassic","Light- to dark-gray, very fine- to medium-grained, well-sorted, quartzite containing interbedded black to dark-gray shale and medium-light- to medium-gray siltstone.  Rare coquina-like beds contain poorly preserved fragments of Buchia and other fossils that provide limited age control.  Unit exposed in the Livengood, western Circle, and eastern Tanana quadrangles.  In the Tanana quadrangle, the Wolverine quartzite includes rocks mapped as the Vrain unit (KJvr) elsewhere (F.R. Weber, unpublished data, 1998","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2816","KJw","Wolverine quartzite","Early Cretaceous or Late Jurassic","Light- to dark-gray, very fine- to medium-grained, well-sorted, quartzite containing interbedded black to dark-gray shale and medium-light- to medium-gray siltstone.  Rare coquina-like beds contain poorly preserved fragments of Buchia and other fossils that provide limited age control.  Unit exposed in the Livengood, western Circle, and eastern Tanana quadrangles.  In the Tanana quadrangle, the Wolverine quartzite includes rocks mapped as the Vrain unit (KJvr) elsewhere (F.R. Weber, unpublished data, 1998","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "2817","KJw","Wolverine quartzite","Early Cretaceous or Late Jurassic","Light- to dark-gray, very fine- to medium-grained, well-sorted, quartzite containing interbedded black to dark-gray shale and medium-light- to medium-gray siltstone.  Rare coquina-like beds contain poorly preserved fragments of Buchia and other fossils that provide limited age control.  Unit exposed in the Livengood, western Circle, and eastern Tanana quadrangles.  In the Tanana quadrangle, the Wolverine quartzite includes rocks mapped as the Vrain unit (KJvr) elsewhere (F.R. Weber, unpublished data, 1998","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "3380","Jgt","Trondhjemite and tonalite","Late and Middle Jurassic","Trondhjemite, tonalite, and subordinate quartz diorite, diorite, and gabbro.  Trondhjemite consists of 50 to 60 percent plagioclase, 25 to  45 percent quartz, 4 to 8 percent mafic minerals (chiefly biotite and subordinate amphibole).  Tonalite has 50 to 55 percent plagioclase, about 20 percent quartz, 5 to 10 percent biotite, and 15 to 25 percent amphibole.  Diorite and gabbro have as much as 30 percent mafic minerals, usually amphibole cored by minor clinopyroxene. Much of the western part of the pluton has been metasomatized by potassium-rich fluids to a pink granite and granodiorite.  In these altered rocks potassium feldspar forms rims on plagioclase grains and occurs as patches or veins replacing plagioclase. The pluton locally has been cataclastically deformed.   Unit is unconformably overlain by andesitic volcaniclastic rocks of unit Kv.  K/Ar isotopic cooling ages range from 173 to 130 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "3496","MzPzum","Mafic-ultramfic complexes","Mesozoic and Paleozoic?","The complexes consist of: 1) a cumulate magmatic suite composed of interlayered dunite, wehrlite, olivine clinopyroxenite, and gabbro, 2) a mantle suite composed of harzburgite, dunite, and minor clinopyoxenite, and 3) a metamorphic sole consisting of a highly tectonized layer of amphibolite, garnet amphibolite, and pyroxene granulite.  The harzburgite in the mantle suite typically is partly to mostly serpentinized. Chromite is generally restricted to centimeter-scale layers in dunite and as an accessory mineral. The complexes are intruded by narrow dikes of fresh clinopyroxenite, hornblendite, gabbro, and gabbro pegmatite.   The complexes are believed to form the roots of the Koyukuk volcanic arc that appears to have been active from Jurassic to late Early Cretaceous  The protolith age of the mantle suite is uncertain and may be as old as Paleozoic. K/Ar isotopic cooling ages from the magmatic suite average 159 Ma and two 40Ar/39Ar determinations yielded a plateau age of 162 Ma.  K/Ar isotopic cooling ages from the metamorphic sole at the base of the complexes range from 172 to 155 Ma and one 40Ar /39Ar determination from the metamorphic sole yielded a plateau age of 161 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "3497","MzPzum","Mafic-ultramfic complexes","Mesozoic and Paleozoic?","The complexes consist of: 1) a cumulate magmatic suite composed of interlayered dunite, wehrlite, olivine clinopyroxenite, and gabbro, 2) a mantle suite composed of harzburgite, dunite, and minor clinopyoxenite, and 3) a metamorphic sole consisting of a highly tectonized layer of amphibolite, garnet amphibolite, and pyroxene granulite.  The harzburgite in the mantle suite typically is partly to mostly serpentinized. Chromite is generally restricted to centimeter-scale layers in dunite and as an accessory mineral. The complexes are intruded by narrow dikes of fresh clinopyroxenite, hornblendite, gabbro, and gabbro pegmatite.   The complexes are believed to form the roots of the Koyukuk volcanic arc that appears to have been active from Jurassic to late Early Cretaceous  The protolith age of the mantle suite is uncertain and may be as old as Paleozoic. K/Ar isotopic cooling ages from the magmatic suite average 159 Ma and two 40Ar/39Ar determinations yielded a plateau age of 162 Ma.  K/Ar isotopic cooling ages from the metamorphic sole at the base of the complexes range from 172 to 155 Ma and one 40Ar /39Ar determination from the metamorphic sole yielded a plateau age of 161 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "3498","MzPzum","Mafic-ultramfic complexes","Mesozoic and Paleozoic?","The complexes consist of: 1) a cumulate magmatic suite composed of interlayered dunite, wehrlite, olivine clinopyroxenite, and gabbro, 2) a mantle suite composed of harzburgite, dunite, and minor clinopyoxenite, and 3) a metamorphic sole consisting of a highly tectonized layer of amphibolite, garnet amphibolite, and pyroxene granulite.  The harzburgite in the mantle suite typically is partly to mostly serpentinized. Chromite is generally restricted to centimeter-scale layers in dunite and as an accessory mineral. The complexes are intruded by narrow dikes of fresh clinopyroxenite, hornblendite, gabbro, and gabbro pegmatite.   The complexes are believed to form the roots of the Koyukuk volcanic arc that appears to have been active from Jurassic to late Early Cretaceous  The protolith age of the mantle suite is uncertain and may be as old as Paleozoic. K/Ar isotopic cooling ages from the magmatic suite average 159 Ma and two 40Ar/39Ar determinations yielded a plateau age of 162 Ma.  K/Ar isotopic cooling ages from the metamorphic sole at the base of the complexes range from 172 to 155 Ma and one 40Ar /39Ar determination from the metamorphic sole yielded a plateau age of 161 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "3851","JMc","Chert, cherty tuff, argillite, crystal-lithic tuff, volcanic breccia, and conglomerate","Jurassic? to Mississippian","Chiefly banded radiolarian chert  interbedded with argillite, cherty  tuff, fine- to coarse-grained crystal and lithic tuff, and volcanic breccia and conglomerate.  Breccia and conglomerate are composed of poorly sorted clasts of mafic volcanic rocks and cherty tuff in a matrix of crystal and lithic tuff.  Unit also includes several small bodies of slightly recrystallized limestone and a few small intrusive bodies of gabbro and diabase.  Unit contains abundant radiolaria ranging in age from Mississippian to possibly as young as Jurassic","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "4032","Trs","Spiculite and sandy limestone","Late Triassic","Composed of quartz-carbonate sandstone and conglomerate in the lower part of unit and spiculitic chert in the upper part.  Sandstone and conglomerate consist of detrital carbonate, quartz, and chert clasts, and calcareous fossil debris.  Spiculite is composed of chert, fine quartz grains, and as much as 60 percent sponge spicules.  Unit contains marine mollusks of Late Triassic (Norian) age in the lower part and radiolaria of probable Triassic age in the upper part
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "4340","Trc","Carbonatite","Triassic","Intensely magnetic dolomite-calcite-magnetite-apatite-rich rock in two sill-like bodies in the southeastern Tanana quadrangle.  40Ar/39Ar age of about 200 Ma reported on contact metamorphic mica reported by Reifenstuhl and others (1998) and interpreted as an intrusion age","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "4880","Mzi","Intrusive rocks","Mesozoic?","Undated parts of the Alaska-Aleutian Range batholith in the Tyonek quadrangle.  Chiefly quartz diorite, diorite, and gabbro (Reed and Elliott, 1970)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5012","TrPs","Sedimentary rocks, undivided","Triassic to Permian","Dominantly dark gray, typically phyllitic, siliceous to carbonaceous argillite and shale, with subordinate but characteristic clast-supported chert-rich conglomerate, greenish-gray chert, tuffaceous volcaniclastic rocks, yellowish- to reddish-brown highly calcareous argillite or limestone, and minor intrusive rocks; locally may include older (Mississippian? or Devonian?) or younger (Cretaceous) rocks (Dover, unpublished data, 1997).  Mapped in Tanana quadrangle.  In Livengood quadrangle, equivalent rocks have been subdivided into two units, Trsc and Ps","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5020","TrMts","Tozitna assemblage (north):  Sedimentary rocks","Triassic to Mississippian","Chert, metachert, metatuff, quartzite, phyllite, and other associated incipiently metamorphosed sedimentary rocks; includes basalt and amygdaloidal pillow basalt in places.  Corresponds to the Rampart Group of Brosge and others (1969) in the Tanana quadrangle, the TRMra, TRMrb, TRMrs, and TRMrl units of Reifenstuhl and others (1997) in the Tanana B-1 quadrangle, and the TRMrs unit of Weber and others (1992) in the Livengood quadrangle and unit PaMc of Foster and others in the Circle quadrangle","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5021","TrMg","Graywacke, grit, and argillite","Triassic? to Mississippian?","Fine- to medium-grained, commonly calcareous graywacke and granule conglomerate, which contain clasts of chert, shale, argillite, and volcanic rocks.   Graywacke and conglomerate are interbedded with argillite.  Unit contains microfossils and bryozoan and echinoids fragments assigned to a Permian(?)  age in the Ruby quadrangle and assigned more generally to a late Paleozoic age in the Ophir quadrangle.  Unit appears to interfinger locally  with unit TrDc
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5112","TrMica","Innoko assemblage:  Chert, argillite, and volcaniclastic rocks","Triassic to Mississippian","Dominantly medium-dark- to dark-gray, thin-banded, bedded radiolarian-bearing chert having thin interbeds of slaty argillaceous rocks, including argillite, slate, and phyllite.  Also includes subordinate intermediate to basaltic volcanic and volcaniclastic rocks including lithic and waterlaid tuff, fossiliferous shallow-water limestone, grit, and arkosic sandstone lenses.  Age range based on radiolaria of Mississippian age, conodonts, and foraminifera of Mississippian age collected from unit in the Ruby and Medfra quadrangles (Chapman and Patton, 1979).  Latest Devonian radiolaria were collected in two localities in the southwestern Ruby quadrangle (Chapman and Patton, 1979) and are the only Devonian fossils known from unequivocal Innoko assemblage rocks; however Patton and others (1994a) report Devonian palynflora from the Wiseman and Christian quadrangles in the similar Angayucham assemblage.  A K-Ar age of 302+/-9 Ma on amphibole from tuff indicates a Pennsylvanian age (Miller and Bundtzen, 1994).  This unit originally described by Chapman and Patton (1979) and redefines part of the Cretaceous chert and argillite unit of Cass (1959, unit Kc).  Corresponds to the TRMc unit of Chapman and others (1985) in the Ophir quadrangle and Miller and Bundtzen (1994) in the Iditarod quadrangle.  Includes the PaMc unit of Patton and others (1980) in the Medfra quadrangle.  Corresponds to the informal MDc unit of Puchner (1984) in the western Ruby quadrangle","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5113","JPztm","Tozitna assemblage (south):  Mafic and ultramafic rocks, undivided","Jurassic? and/or Paleozoic?","Gabbro sills and subordinate quartz diorite, quartz monzonite, and pyroxenite.  Undated; age and assignment to the Tozitna assemblage based on lithologic associations and regional comparisons.  Corresponds to informal Pzmi unit of Puchner (1984) in western Ruby quadrangle","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5120","MzPzi","Intrusive and volcanic rocks, undivided","Mesozoic or Paleozoic","Granodiorite of Rainbow Mountain in the Mount Hayes quadrangle (unit grrm, Nokleberg and others, 1992a), diorite in the Circle and Bid Delta quadrangles (unit MzPzd, Foster and others, 1983; unit Pzd, Weber and others, 1978), and gabbro and quartz diorite in the Talkeetna, Tyonek, and McGrath quadrangles (unit MzPzg, Reed and Nelson, 1980; unit MzPzm, Magoon and others, 1976; unit MzPzi, Bundtzen and others, 1997a, T.K. Bundtzen, written commun., 1997).  Also dark-gray to greenish-gray dikes ranging from basalt to granodiorite in the Talkeetna quadrangle (unit MzPzi, Reed and Nelson, 1980) and volcanic rocks of unknown age in the Nulato and the Lime Hills quadrangles (unit vr, W.W. Patton, Jr., written commun., 1997; unit MzPzi, Reed and Gamble, 1988)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5130","JTrtmu","Tozitna assemblage (north):  Mafic and ultramafic rocks","Jurassic? to Triassic","Diabase, gabbro, leucogabbro, and greenstone; ultramafic rocks include serpentinized peridotite, harzburgite, and werhlite.  Locally, may include minor associated sedimentary rocks.  Tentative age range based on K-Ar age of 210+/-6 Ma reported by Brosge and others (1969; age recalculated using constants of Steiger and Jager, 1977) on gabbro in Rampart Group, and stratigraphic and/or intrusive relationship with rocks as young as Triassic.  Includes unit TRMrg in the Tanana B-1 quadrangle (Reifenstuhl and others, 1997), unit TRMrv in the Livengood quadrangle (Weber and others, 1992) (Foster and others, 1983)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5131","TrMbc","Pillow  basalt, chert, and minor agglomerate","Triassic? to Mississippian?","Altered aphanitic and porphyritic pillow basalt.  Phenocrysts in the porphyritic basalt are composed chiefly of olivine and pyroxene.  Basalt is interlayered with chert and subordinate beds of agglomerate containing clasts of basalt and chert.  Chert contains bryozoans and radiolari a of late Paleozoic and possibly Triassic age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5132","JMtru","Tozitna assemblage (north):  Greenstone, chert, and ultramafic rocks, undivided","Jurassic? to Mississippian?","Poorly dated spilitic basalt and diabase largely altered to greenstone.  Locally, includes minor sedimentary rocks, generally low metamorphic grade cataclastic assemblage of generally dark gray chert and siliceous argillite.  Also includes subordinate volcaniclastic rocks and minor Mississippian limestone.  Mafic, ultramafic, and associated metasedimentary rocks of the Tozitna terrane of Silberling and Jones (1984; see fig.2, herein) in the Tanana and Circle quadrangles are part of this unit.  Similar rocks occur on strike to the northeast in the Bettles quadrangle (Patton and Miller, 1973).  Includes unit TRPv in the Tanana (Chapman and others, 1975) quadrangle, unit TRMru in the Tanana quadrangle (Reifenstuhl and others, 1997), and unit MzPzc, the Circle Volcanics, in the Circle quadrangle (Foster and others, 1983).  The origin, original setting, and tectonic emplacement of these rocks are discussed by Churkin and others (1982), Coney and Jones (1985), Gemuts and others (1983), Dover (1994), Foster and others, 1994, and Patton and others, 1994a","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5133","JMtu","Tozitna assemblage (south):  Mafic, ultramafic, and sedimentary rocks, undivided","Jurassic to Mississippian","Basalt, gabbro, diabase, basaltic tuff, and chert.  May include minor ultramafic rocks and other associated low metamorphic grade metasedimentary rocks in the Nulato, Ophir, and Ruby quadrangles that resemble the Tozitna assemblage north of the Kaltag fault interpreted as an offset equivalent.  Poorly dated.  Corresponds to the eastern parts of unit TRMb of Patton (written commun., 1997) in the Nulato quadrangle, unit TrMb in the Ophir quadrangle (Chapman and others, 1985), and parts of units mc and mi in the Ruby quadrangle (Cass, 1959).  A large area in the northwest part of the Ruby quadrangle is shown as this unit; however, we believe on the basis of information from R.M. Chapman (oral commun., 1998) that unit JMtu primarily occurs capping ridges and that rocks of the Ruby metamorphic complex occur at lower elevations.  Further mapping will be necessary to resolve the geology of this area","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5140","JDv","Altered basalt, gabbro, chert, argillaceous rocks, tuff, graywacke, and carbonate rocks","Jurassic to Devonian","Variably altered and metamorphosed flows and shallow intrusives of basalt, diabase, and gabbro interbedded with varying proportions of chert, argillite, slate, phyllite, volcaniclastic rocks,  graywacke, and carbonate rocks. The basalt, diabase, and gabbro are weakly metamorphosed to prehnite-pumpellyite facies and generally increase in metamorphic grade structurally downward.  Greenschist facies metamorphism and locally high-pressure blueschist metamorphism, as indicated by the presence of glaucophane and lawsonite, occur near the base of the terrane where it strucurally overlies the Ruby terrane.  The chert includes both interpillow and bedded varieties and ranges from pure radiolarian and spiculitic chert to cherty tuff.  In the southeastern part of the Nulato quadrangle and adjoining parts of the Ruby quadrangle, the unit is characterized by sill-like bodies of diabase and gabbro, argillaceous rocks, fine-grained to conglomeritic graywacke, and chert.  Radiolaria from chert  in this unit range in age from Devonian to Jurassic.  Sparse megafossils from the carbonate rocks range in age from Devonian to Permian. The carbonate rocks in the lower part of the unit contain redeposited shallow-water conodont faunas that range in age from Ordovician to Late Mississippian
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5145","KJm","Melange","Early Cretaceous? and Jurassic","Melange consists of blocks of carbonate rocks, chert, metagraywacke, and altered mafic volcanic and intrusive rocks in a matrix of phyllite.  Within the melange unit the large blocks of carbonate rocks from units  |ca and |cr  and altered basalt, diabase, and gabbro from unit JDv are mapped separately.  Melange probably formed during time of tectonic emplacement of Angayucham-Tozitna terrane structurally above Arctic Alaska and Ruby terranes.
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5150","MzPzum","Mafic-ultramfic complexes","Mesozoic and Paleozoic?","The complexes consist of: 1) a cumulate magmatic suite composed of interlayered dunite, wehrlite, olivine clinopyroxenite, and gabbro, 2) a mantle suite composed of harzburgite, dunite, and minor clinopyoxenite, and 3) a metamorphic sole consisting of a highly tectonized layer of amphibolite, garnet amphibolite, and pyroxene granulite.  The harzburgite in the mantle suite typically is partly to mostly serpentinized. Chromite is generally restricted to centimeter-scale layers in dunite and as an accessory mineral. The complexes are intruded by narrow dikes of fresh clinopyroxenite, hornblendite, gabbro, and gabbro pegmatite.   The complexes are believed to form the roots of the Koyukuk volcanic arc that appears to have been active from Jurassic to late Early Cretaceous  The protolith age of the mantle suite is uncertain and may be as old as Paleozoic. K/Ar isotopic cooling ages from the magmatic suite average 159 Ma and two 40Ar/39Ar determinations yielded a plateau age of 162 Ma.  K/Ar isotopic cooling ages from the metamorphic sole at the base of the complexes range from 172 to 155 Ma and one 40Ar /39Ar determination from the metamorphic sole yielded a plateau age of 161 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5190","MzPzum","Mafic-ultramfic complexes","Mesozoic and Paleozoic?","The complexes consist of: 1) a cumulate magmatic suite composed of interlayered dunite, wehrlite, olivine clinopyroxenite, and gabbro, 2) a mantle suite composed of harzburgite, dunite, and minor clinopyoxenite, and 3) a metamorphic sole consisting of a highly tectonized layer of amphibolite, garnet amphibolite, and pyroxene granulite.  The harzburgite in the mantle suite typically is partly to mostly serpentinized. Chromite is generally restricted to centimeter-scale layers in dunite and as an accessory mineral. The complexes are intruded by narrow dikes of fresh clinopyroxenite, hornblendite, gabbro, and gabbro pegmatite.   The complexes are believed to form the roots of the Koyukuk volcanic arc that appears to have been active from Jurassic to late Early Cretaceous  The protolith age of the mantle suite is uncertain and may be as old as Paleozoic. K/Ar isotopic cooling ages from the magmatic suite average 159 Ma and two 40Ar/39Ar determinations yielded a plateau age of 162 Ma.  K/Ar isotopic cooling ages from the metamorphic sole at the base of the complexes range from 172 to 155 Ma and one 40Ar /39Ar determination from the metamorphic sole yielded a plateau age of 161 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5208","TPza","Amphibolite facies metamorphic rocks","Earliest Tertiary to Paleozoic","Dominantly medium- to medium-dark-gray garnetiferous quartz-mica schist and amphibolite, but includes slate and shale in the Livengood quadrangle.  Locally has gneissic texture.  Minor marble and very minor quartzite occur in unit in the Tanana quadrangle.  Unit outcrops as large fault slivers or ""lozenges"" along a strand of the Tintina-Kaltag fault system in the Livengood (Weber and others, 1992) and Tanana quadrangles (Reifenstuhl and others, 1997).  In the Tanana quadrangle, geophysical interpretation cited in Reifenstuhl and others (1997) and outcrop patterns suggest a steep northwest contact with rocks of the Tozitna assemblage and a moderately southeast dipping southeast contact.  Protolith age is unknown and although Reifenstuhl and others (1997) and Dusel-Bacon and others (1989) suggest a Ruby or Yukon-Tanana metamorphic complex origin, Weber and others (1992) suggest a possible protolith of Tozitna sedimentary rocks.  Includes the Raven Creek Hill unit of Weber and others (1992) and units pTam, pTas, pTaq of Reifenstuhl and others (1997)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5241","MzZma","Metabasite","Mesozoic? to Proterozoic?","Varies from thinly layered greenschist to more massively layered greenstone bodies representing altered mafic and intermediate volcanic and  shallow intrusive rocks. The characteristic mineral are chlorite, albite, actinolite, and epidote.  Unit may include rocks of several different ages.  Some of the bodies are interlayered with the Devonian felsic schist of unit Df and are part of a bimodal volcanic  assemblage.  Other bodies are interlayered with carbonate rocks (unit |ca) that contain fossils of probable Devonian and Mississippian age.  Still other bodies may represent tectonically emplaced  slices of unit JDv of the Angayucham-Tozitna terrane
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5242","MzZmr","Metabasite","Mesozoic? to Proterozoic?","Massive greenstone to thinly layered greenschist bodies that probably represent metamorphosed mafic to ultramafic intrusive rocks and mafic to intermediate flows and tuffs.  Unit  is intercalated with with units PzZsr Pzcr, and Dgnr.","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5243","MzZms","Metabasite","Mesozoic? to Proterozoic?","Greenstone and greenschist bodies representing altered mafic and intermediate volcanic and intrusive rocks","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5280","JDv","Altered basalt, gabbro, chert, argillaceous rocks, tuff, graywacke, and carbonate rocks","Jurassic to Devonian","Variably altered and metamorphosed flows and shallow intrusives of basalt, diabase, and gabbro interbedded with varying proportions of chert, argillite, slate, phyllite, volcaniclastic rocks,  graywacke, and carbonate rocks. The basalt, diabase, and gabbro are weakly metamorphosed to prehnite-pumpellyite facies and generally increase in metamorphic grade structurally downward.  Greenschist facies metamorphism and locally high-pressure blueschist metamorphism, as indicated by the presence of glaucophane and lawsonite, occur near the base of the terrane where it strucurally overlies the Ruby terrane.  The chert includes both interpillow and bedded varieties and ranges from pure radiolarian and spiculitic chert to cherty tuff.  In the southeastern part of the Nulato quadrangle and adjoining parts of the Ruby quadrangle, the unit is characterized by sill-like bodies of diabase and gabbro, argillaceous rocks, fine-grained to conglomeritic graywacke, and chert.  Radiolaria from chert  in this unit range in age from Devonian to Jurassic.  Sparse megafossils from the carbonate rocks range in age from Devonian to Permian. The carbonate rocks in the lower part of the unit contain redeposited shallow-water conodont faunas that range in age from Ordovician to Late Mississippian
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5285","Pzrmi","Ruby metamorphic complex -- Metamorphosed mafic igneous rocks","Paleozoic?","Metamorphosed mafic igneous rocks, ranging from metagabbro and metadiabase to greenstone, amphibolite, and garnet amphibolite.  Variable intensity of sheared within unit.  Unit Pzm of Dover (unpublished mapping, 1997), not mapped separately by Chapman and others (1982)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5295","MzZfm","Metabasite (MzZma) and felsic schist (Df), undivided ","Mesozoic? to Proterozoic?","Metabasite (MzZma) and felsic schist (Df), undivided ","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5310","DCd","East Fork Hills Formation","Devonian to Cambrian","Deep-water deposits of finely laminated limestone and dolomitic limestone.  Subordinate chert and siliceous siltstone.  Formation was originally assigned an Ordovician to Devonian age on the basis of a sparse conodont fauna (Dutro and Patton, 1982. More recent work, however, indicates that it also contains conodonts of Cambrian age (Dumoulin and others, 1997)
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5320","Pzcs","Carbonate rocks","Paleozoic","Chiefly massively bedded light gray to tan dolomitic and calcareous marble.  Locally interbedded black to dark gray calcareous marble and subordinate impure marble and calcareous schist.  Unit locally contains an abundant conodont fauna of Ordovician to Devonian age","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5321","PzZus","Pelitic schist, calc schist, and quartzite (PzZss) and carbonate rocks (Pzcs), undivided","Paleozoic and Proterozoic?","Scattered exposures along the western edge of the map area extending from the Norton Bay quadrangle to the southwestern part of the Selawik quadrangle",""
    "5322","PzZss","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic?","Quartz-muscovite-graphite schist, calc schist, quartzofeldspathic schist, phyllite, and quartzite.  Unit is locally interlayered with unit |cs and is therefore, at least in part, Paleozoic in age.  Some of the unit may be as old as Proterozoic.  Samples of the schist yielded a metamorphic mineral K/Ar isotopic cooling age of 124 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "5340","Pzcr","Carbonate rocks","Paleozoic","Gray to white, partly to wholly recrystallized limestone, marble, dark-gray dolomitic marble, and impure schistose limestone.  Unit occurs in layers as much as 25m thick intercalated with quartz-mica schist, mica schist, graphitic schist, metabasite, and quartzite.  Some contacts are gradational; others are sharp and may be faulted.  Unit contains conodonts of Middle Ordovician age in the Nulato quadrangle and  poorly preserved corals of Ordovician to Late Mississippian age in the Ruby quadrangle
","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5410","Pzvs","Volcanic and sedimentary rocks","late or middle Paleozoic","Dark-greenish-gray mafic volcanic rocks and interbeds of black phyllite, chert-pebble conglomerate, light-green tuff, and graywacke (Reed and Nelson, 1980).  Volcanic rocks include pillow basalt, breccia agglomerate, tuff, and massive basalt flows.  Distinguished from unit Trpb (this map, unit Pzbs, Reed and Nelson, 1980) by presence of massive basalt flows","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5521","MzZrc","Complex of the Reindeer Hills","Mesozoic to Proterozoic?","Undivided assemblage of interlayered impure marble, quartz-mica schist, and quartzite intruded by aplite  and amphibolite dikes.  Includes some ductily deformed metasomatized contact marble with biotite- and epidote-rich bands.  Field data are insufficient  to map separately  the complexly interrelated lithologic components of this assemblage.  Marble, schist, and quartzite probably are correlative with units |cs and |<ss exposed in northwestern part of Norton Bay quadrangle.  An aplite dike in the complex yielded a K/Ar isotopic cooling age of 120 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5525","Pzca","Carbonate rocks","Paleozoic","Ranges from light gray to white partly recrystallized limestone  to coarsely crystalline marble. Dark finely crystalline dolomitic marble.  Interbedded calc schist, chloritic schist, and quartzite in subordinate amounts.  Unit ranges in age from Ordovician to Mississippian and may  locally include  rocks as old as Cambrian. Contains scattered fossils, chiefly conodonts, from map area and from exposures of the unit in contiguous parts of the Arctic Alaska terrane north of the map area
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5542","MzPzq","Quartzite, grit, argillite, and quartz-mica schist","early Paleozoic and Proterozoic?","Mixed assemblage of laminated fine-to coarse-grained quartzite, grit, and argillite grading upward into very fine-grained quartzite, argillite, phyllite, and chert.  In southeast corner of Medfra quadrangle unit is metamorphosed to greenschist facies composed of sheared and foliated grit, quartzite, quartz-muscovite schist, and subordinate thin carbonate rocks and metachert.  No fossils found in this unit in the Medfra quadrangle, but to the east in the adjoining Mt. McKinley quadrangle it contains fossils of Silurian and Devonian age (Dumoulin and others, 1997).  In the southeastern part of the Medfra quadrangle the unit is interlayered with mafic igneous rocks that yielded a K/Ar isotopic cooling age of 421 Ma.  Unit may include rocks as old as Proterozoic
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5560","Pzpa","Phyllite and subordinate metagraywacke","Paleozoic?","Dark phyllite and minor metagraywacke that have a penetrative fabric ranging from slaty cleavage to weakly schistose.  Unit locally contains slices of little deformed shallow-water Devonian carbonate rocks that are enveloped in basalt flows and debris-flow(?) breccias composed of blocks of vesicular basalt in a matrix of volcanic and carbonate debris.  Age of unit is probably middle or late Paleozoic.  Correlative with |pr unit in the Ruby terrane
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5561","Pzpr","Phyllite","Paleozoic?","Phyllite and subordinate fine-grained metagraywacke cut by abundant vein quartz.  The phyllite and metagraywacke are overprinted by a low-grade penetrative metamorphic fabric, but turbidite features, such as sole marks and graded bedding, are locally discernible.  Age of unit is uncertain,  probably Devonian or late Paleozoic.  Correlative with unit Pzpa in the Arctic Alaska terrane","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5565","Pzg","Metagraywacke and subordinate phyllite","Paleozoic?","Fine- to medium-grained metagraywacke and metasiltstone  composed chiefly of quartz and chert clasts, but in places containing a significant component of volcanic rock and feldspar clasts.  Overprinted by low-grade penetrative metamorphic fabric, but turbidite features, such as graded bedding and sole marks, are locally discernible.  Interbedded with subordinate amounts of phyllite","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5615","PDms","Sedimentary rocks","Permian? to Devonian?","Indeterminate or poorly identified units in Livengood quadrangle.  Black and greenish-gray siliceous slate, thinly interbedded gray chert, shaly chert, and minor breccia, siliceous, locally sandy siltstone displaying turbiditic sedimentary structures, red and greenish-gray, or dark-gray, locally calcareous shale, phyllite, minor quartz- sandstone, argillite, greenstone, lime mudstone to packstone, and limestone debris flows.  Conodonts from a limestone clast in one debris flow indicate a Late Devonian (Famennian) age (Weber and others, 1992).  Includes units PDms and Pzs in the Livengood quadrangle (Weber and others, 1992)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "5740","Ps","Sanstone, sandy limestone, and conglomerate","Permian","Fine- to coarse-grained sandstone, limy sandstone, sandy limestone, siltstone and shale.  Sandstone ranges from clean quartz arenite to a lithic arenite containing as much as 25 percent muscovite and metamorphic rock fragments.   Where unit unconformably overlies units Pzs and Pzc, it contains a basal conglomerate that has large clasts of calc schist, quartz-mica schist, and chlorite schist in a micaceous and sandy matrix.  Unit locally contains an abundant Permian brachiopod fauna.","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "5745","TrMg","Graywacke, grit, and argillite ","Triassic? to Mississippian?","Fine- to medium-grained, commonly calcareous graywacke and granule conglomerate, which contain clasts of chert, shale, argillite, and volcanic rocks.   Graywacke and conglomerate are interbedded with argillite.  Unit contains microfossils and bryozoan and echinoid fragments assigned to a Permian(?)  age in the Ruby quadrangle and assigned more generally to a late Paleozoic age in the Ophir quadrangle.  Unit appears to interfinger locally  with unit TrDc
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6080","TrDc","Chert, argillite, and limestone","Triassic? to Devonian","Varicolored radiolarian chert, lenticular beds of fossiliferous limestone and interbedded argillite.  Subordinate beds of sandy limestone, grit, and arkosic sandstone.  Unit contains abundant radiolaria, condonts, and foraminifera that range in age from latest Devonian to possibly as young as Triassic
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6522","Dgnr","Granitic gneiss","Devonian","Strongly foliated quartzofeldspathic gneiss.  Consists of a coarse- to medium-grained porphyroclastic biotite-quartz-feldsparmuscovite mylonite gneiss containing resistant augen of K-feldspar in a ductile matrix of mica, quartz, and feldspar.   A U/Pb zircon determination from unit in the Tanana quadrangle yielded  a crystallization  age of 390 Ma, which suggests that it is approximately the same age as unit Dgna in the Arctic Alaska terrane
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6523","Dgna","Granitic gneiss","Devonian","Foliated gneissic granite composed of albite, potassium feldspar, quartz, muscovite, and biotite.  Intruded by aplite dikes.  Pluton yielded a probable Devonian U/Pb zircon crystallization age.  Correlative in age with unit Dgnr in the Ruby terrane
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6530","Mgq","Globe quartzite","Mississippian","Light gray, massive or thinly laminated quartzite and medium- to dark-gray slate, phyllite, and laminated claystone.  Unfossiliferous; age inferred on the basis of intrusion by Triassic rocks and by lithologic and stratigraphic similarity with the Keno Hill quartzite of Yukon Territory, Canada (Dover, 1994).  Associated with gabbroic dikes and sills.  Occurs in the White Mountains and Schwatka stratigraphic belts in Livengood and Tanana quadrangles and has limited exposure in the Circle quadrangle (F.R. Weber, unpublished mapping, 1998)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "6620","DSp","Paradise Fork Formation","Early Devonian and Silurian","Deep-water turbiditic and hemipelagic deposits of dark, thin-bedded, fissile to laminated limestone, limy shale, and siltstone.  The formation has an abundant graptolite, conodont, and ostracod fauna.  It was originally assigned an Early to Late Silurian age by Dutro and Patton (1982), but subsequent investigations by Dumoulin and others (1997) indicate that it ranges from Silurian to Early Devonian","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6680","SZa","Amy Creek unit","Silurian to Late Proterozoic","In Livengood quadrangle were described by Weber and others (1992), consists chiefly of medium-grained gray dolostone, and light-gray, yellow-gray, or buff dolomitic mudstone, packstone, and wackestone.  Coarser-grained rocks show abundant peloids and crossbedding; laminations present in mudstone; solution breccia and algal coatings present.  Other interbedded rock types include chert, black argillite, lime mudstone, basaltic greenstone, tuff, tuffaceous siltstone, shale, and minor volcaniclastic graywacke (Weber and others, 1992).  In the Tanana quadrangle, consists of white, massive, locally laminated cherty dolostone having gray limestone at top and bottom of section (Dover, unpublished mapping, 1997).  In the Circle quadrangle, consists of yellow-gray dolomite and gray to dark-gray and black argillite, shale, and siltstone, interlayered with light- and dark-gray chert, gray marble, and gray, fine-grained quartzite (Foster and others, 1983).  Age poorly constrained; age range given here is from Weber and others (1992).  Must be older than the fossiliferous Middle Devonian strata that overlie it, and at least in part Cambrian or younger because it has yielded sponge spicules and unidentifiable radiolaria","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "6910","Dtr","Troublesome unit and possibly correlative rocks","Devonian?","Rhythmically interbedded dark-gray to black cherty argillite to chert, and thin beds of black to gray, siliceous slate as mapped in the Livengood quadrangle.  Associated with extensive mafic intrusive and extrusive rocks.  Unidentified radiolaria are only reported fossils (Weber and others, 1992).  Depositionally overlain by Frasnian carbonate buildups at base of Quail unit, hence Middle Devonian or older.  Also includes unit Pzc in the Circle quadrangle, which consists of chert interlayered with argillite, and rare marble and quartzite, intruded by diorite and gabbro (Foster and others, 1983).  Radiolaria from unit Pzc are not age-diagnostic but reported as ""possibly of Mississippian age (Foster and others, 1983)""; this constraint is, however, less compelling than the pre-Frasnian age for the Troublesome unit in its type area.  May correlate with the McCann Hill Chert of the Charley River quadrangle (Brabb and Churkin, 1969","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "6956","Pzlsl","Schist, phyllite, limestone, and greenstone","Early Paleozoic","Light- to medium-green chloritic schist, light- to medium-gray with silvery sheen phyllite, light- to medium-gray and greenish-gray, sandy in part, largely recrystallized limestone, and light- to medium-green greenstone.  Schist and phyllite are partly calcareous, intensely folded and interbedded with thin limestone beds.  Greenstone is basaltic, less common than other rock types.  Unfossiliferous; probably older than the adjacent Frasnian limestone (unit DSl).  Mapped only in the western Kantishna River quadrangle (Chapman and others, 1975","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "6960","DSw","Whirlwind Creek Formation","Devonian and late Silurian","Shallow-water deposits consisting of several repeated cycles.  In the lower part of the formation the cycles grade from algal laminated dolomite into pelletoidal limestone and then into silty limestone and siltstone.  In the upper part  the cycles grade from thick-bedded reefy limestone into thin-bedded limestone.  The formation contains an abundant Late Silurian and Devonian  conodont, brachiopod, coral, and ostracod fauna","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "6966","DSt","Tolovana Limestone","Middle Devonian to Early Silurian","Lower part of alternating green and maroon lime mudstone, succeeded by yellowish-brown weathering, silty to shaly lime mudstone and wackestone, and a main, upper part of light-weathering peloid- and ooid-rich lime packstone and grainstone and rare dolostone in the White Mountains of east-central Livengood quadrangle.  Conodonts, brachiopods, and corals indicate an Early Silurian age.  In the same strike belt in southeastern Livengood quadrangle, a somewhat younger (Middle Devonian) unit of lime mudstone and wackestone has also been assigned to the Tolovana Limestone; this subunit continues into the Fairbanks and Kantishna River quadrangles.  Rocks formerly assigned to the Tolovana Limestone in northwesternmost Circle quadrangle are herein assigned to the Schwatka unit (unit Ds); rocks formerly assigned to the Tolovana Limestone in north-central and northeastern Circle quadrangle are herein to unit DSl.  Depositional environment interpreted as shallow marine","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "7261","Df","Felsic schist","Devonian","Schistose felsic volcanic rocks, including flows, tuffs, and porphyritic hypabyssal? rocks, interlayered with metasedimentary rocks belonging to units  |<sa and |ca.  An important component of this unit is the widely recognized ""button schist"" -a porphyritic rhyolite composed of quartz megacrysts and albite porphyroblasts in a groundmass of quartz, potassium feldspar, and muscovite.  Unit yielded Devonian U/Pb and Pb/Pb zircon crystallization ages and is interlayered with carbonate rocks containing fossils of probable middle Paleozoic age
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7350","Dcs","Calcareous schist","Devonian","Light-brown weathering calcareous schist interbedded with gray quartz-mica schist and marble.  Brooks Range schist belt.","Patton, W.W., Jr., and Miller, T.P., 1973, Bedrock geologic map of Bettles and southern part of Wiseman quadrangles, Alaska:  U.S. Geological Survey Miscellaneous Field Studies Map MF-492, scale 1:250,000."
    "7450","PzZua","Pelitic schist, calc schist, and quartzite (|<sa) and carbonate rocks (|ca), undivided","Paleozoic and Proterozoic","","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7451","PzZsa","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic","Quartz-mica schist and lesser amounts of calc schist, quartzite, graphitic  schist, chlorite schist, and quarto-feldspathic schist. Polydeformed greenschist-blueschist-facies characterized by quartz-muscovite-chlorite-albiteglaucophane   assemblages. A relict epidote-amphibolite metamorphic assemblage suggests that, at locally, the unit underwent a pre-mid Devonian metamorphic event.  Unit is interbedded with carbonate rocks of unit |ca and therefore is, in part, Paleozoic in age.  However, in the Baird Mountains quadrangle, unit is intruded by Proterozoic granitic rocks of unit PzZi, and therefore is locally as old as Proterozoic. K/Ar isotopic analyses of the schist yielded Early Cretaceous metamorphic mineral cooling ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7453","PzZsa","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic","Quartz-mica schist and lesser amounts of calc schist, quartzite, graphitic  schist, chlorite schist, and quarto-feldspathic schist. Polydeformed greenschist-blueschist-facies characterized by quartz-muscovite-chlorite-albiteglaucophane   assemblages. A relict epidote-amphibolite metamorphic assemblage suggests that, at locally, the unit underwent a pre-mid Devonian metamorphic event.  Unit is interbedded with carbonate rocks of unit |ca and therefore is, in part, Paleozoic in age.  However, in the Baird Mountains quadrangle, unit is intruded by Proterozoic granitic rocks of unit PzZi, and therefore is locally as old as Proterozoic. K/Ar isotopic analyses of the schist yielded Early Cretaceous metamorphic mineral cooling ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7454","PzZsa","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic","Quartz-mica schist and lesser amounts of calc schist, quartzite, graphitic  schist, chlorite schist, and quarto-feldspathic schist. Polydeformed greenschist-blueschist-facies characterized by quartz-muscovite-chlorite-albiteglaucophane   assemblages. A relict epidote-amphibolite metamorphic assemblage suggests that, at locally, the unit underwent a pre-mid Devonian metamorphic event.  Unit is interbedded with carbonate rocks of unit |ca and therefore is, in part, Paleozoic in age.  However, in the Baird Mountains quadrangle, unit is intruded by Proterozoic granitic rocks of unit PzZi, and therefore is locally as old as Proterozoic. K/Ar isotopic analyses of the schist yielded Early Cretaceous metamorphic mineral cooling ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7455","PzZsa","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic","Quartz-mica schist and lesser amounts of calc schist, quartzite, graphitic  schist, chlorite schist, and quarto-feldspathic schist. Polydeformed greenschist-blueschist-facies characterized by quartz-muscovite-chlorite-albiteglaucophane   assemblages. A relict epidote-amphibolite metamorphic assemblage suggests that, at locally, the unit underwent a pre-mid Devonian metamorphic event.  Unit is interbedded with carbonate rocks of unit |ca and therefore is, in part, Paleozoic in age.  However, in the Baird Mountains quadrangle, unit is intruded by Proterozoic granitic rocks of unit PzZi, and therefore is locally as old as Proterozoic. K/Ar isotopic analyses of the schist yielded Early Cretaceous metamorphic mineral cooling ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7520","Ont","Novi Mountain and Telsitna Formations, undivided","Ordovician","Novi Mountain Formation: Shallow water deposits.  Predominately calcareous siltstone and shale in lower part.  Upper part characterized by cycles beginning with massive limestone commonly containing flat carbonate pebbles at the base and grading upward through thin irregularly bedded shaly limestone into calcareous siltstone or shale at the top.  The formation contains a sparse Early Ordovician conodont fauna. 
Telsitna Formation: Chiefly shallow water limestone and dolomite.  The lower part dominated by highly fossiliferous thin-bedded fine-grained limestone containing silty interbeds.  Middle part consists chiefly of nonfossiliferous dolomite.  The upper part is composed mainly of limestone that ranges from thick bedded and fine-grained to thin-bedded and silty.  Stringers and nodules of black chert occur near the top.  The upper part locally is characterized by platy dark limestone containing conodonts indicative of deep-water deposition.   The formation contains an abundant conodont, brachiopod, and coral fauna.  It was  originally assigned a Middle and Late Ordovician age by Dutro and Patton (1982), but subsequent investigations by Dumoulin and others (1997) indicate that it ranges from Early to Late Ordovician
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7581","Oc","Chert and argillite","Ordovician","Banded chert, argillite, fine-grained thin-bedded limestone, and silty dolomite.  Beds separated by carbonaceous partings.  Unit interpreted to be a deep-water sequence composed of turbiditic and hemipelagic deposits.   Unit locally contains conodonts and graptolites of Early and Middle Ordovician age in the Medfra quadrangle and east of the map area in adjoining parts of the Mt. McKinley quadrangle
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "7610","Ofc","Fossil Creek Volcanics","Ordovician","Two members, one largely volcanic, one largely sedimentary.  Volcanic member consists of alkali basalt, agglomerate, and volcaniclastic conglomerate.  Agglomerate and conglomerate contain well-rounded clasts of basalt, granite, quartzite, limestone, chert, and phyllite.  Sedimentary member consists of shale, chert, and limestone which are intruded by gabbro.  Late Ordovician brachiopods, trilobites, gastropods, and conodonts have been recovered from sedimentary rocks in the volcanic member; Early Ordovician conodonts and trilobites have been recovered from the sedimentary member (Weber and others, 1992).  Mapped in the White Mountains stratigraphic belt of Livengood, Circle, and Tanana quadrangles (Dover, 1994).  Laterally equivalent to Livengood Dome Chert","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "7710","Olc","Chert","Ordovician","Dark gray and black chert, siliceous slate, argillite, and less abundant greenstone, impure limestone, and dolostone.  Age assigned on basis of graptolites.  Includes the Livengood Dome Chert in the Livengood, Circle, and Tanana quadrangles, unit Pzlc in Tanana quadrangle (Dover, unpublished mapping, 1997), the Nilkoka Group in Fairbanks quadrangle (Pewe and others, 1966), and unit DOc in Mount McKinley and Kantishna River quadrangles (Bela Csejtey, Jr., written commun., 1993; Chapman and others, 1975)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "7711","Ocl","Limestone","Paleozoic?","Distinctive marker bed of lime mudstone within chert unit, locally characterized by coated ooids.  Thickness varies from 10 to several ten's of meters, probably in part due structural thickening and repetition.  Only mapped locally.  Corresponds to unit Pzl, in part, of Chapman and others (1982) in the Tanana quadrangle ","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "8300","PzZq","Quartzite, grit, argillite, and quartz-mica schist","early Paleozoic and Proterozoic?","Mixed assemblage of laminated fine-to coarse-grained quartzite, grit, and argillite grading upward into very fine-grained quartzite, argillite, phyllite, and chert.  In southeast corner of Medfra quadrangle unit is metamorphosed to greenschist facies composed of sheared and foliated grit, quartzite, quartz-muscovite schist, and subordinate thin carbonate rocks and metachert.  	No fossils found in this unit in the Medfra quadrangle, but to the east in the adjoining Mt. McKinley quadrangle it contains fossils of Silurian and Devonian age (Dumoulin and others, 1997).  In the southeastern part of the Medfra quadrangle the unit is interlayered with mafic igneous rocks that yielded a K/Ar isotopic cooling age of 421 Ma.  Unit may include rocks as old as Proterozoic
","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "8310","CZwa","Wickersham grit, Argillaceous upper unit","Cambrian? and Late Proterozoic","Dominantly argillaceous, containing distinctive tan-weathering gray calcareous siltstone and fine-grained sandstone, subordinate quartzite and chert, and locally, a few black clastic limestone interbeds.  Corresponds to the CZwa unit of Weber and others (1992) in the Livengood quadrangle, unit ng of Pewe and others (1966) in the Fairbanks quadrangle, and the PzpCa unit of Foster and others (1983) in the Circle quadrangle","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "8500","PzZi","Granitic gneiss","Paleozoic? and Proterozoic","Granite, granodiorite, diorite, and gabbro that have  a slight to moderate gneissic fabric.  The northwesternmost of the two bodies is Proterozoic  and has yielded a U/Pb zircon crystallization  age of 705 Ma.   The southeasternmost body is of uncertain age.  It may also be Proterozoic or it may be Devonian and correlative with unit Dgna","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8601","PzZsr","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic?","Quartz-mica schist, chlorite schist, quartzofeldspathic schist, quartzite, and micaeous and graphitic schist.  Regionally metamorphosed to greenschist-facies, but also locally includes high-pressure greenschist-blueschist-facies (distinguished by the presence of glaucophane) and amphibolite-facies (distinguished by the presence of sillimanite and kyanite).  Andalusite-cordierite hornfels and contact schist occur in broad bands around Cretaceous granitic bodies of units Kgr and Ksy.   Unit locally is interlayered with carbonate rocks of unit |cr and therefore is, at least in part, Paleozoic in age.  However, some of the unit may be as old as Proterozoic.  The regional metamorphism clearly pre-dates the widespread intrusion of the Early Cretaceous granitic bodies of units Kgr and Ksy.  Metamorphic minerals in this unit in the Nulato quadrangle yielded  K/Ar isotopic cooling ages of 134 and 136 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8602","PzZsa","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic","Quartz-mica schist and lesser amounts of calc schist, quartzite, graphitic  schist, chlorite schist, and quarto-feldspathic schist. Polydeformed greenschist-blueschist-facies characterized by quartz-muscovite-chlorite-albiteglaucophane   assemblages. A relict epidote-amphibolite metamorphic assemblage suggests that, at locally, the unit underwent a pre-mid Devonian metamorphic event.  Unit is interbedded with carbonate rocks of unit |ca and therefore is, in part, Paleozoic in age.  However, in the Baird Mountains quadrangle, unit is intruded by Proterozoic granitic rocks of unit PzZi, and therefore is locally as old as Proterozoic. K/Ar isotopic analyses of the schist yielded Early Cretaceous metamorphic mineral cooling ages
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8605","PzZua","Pelitic schist, calc schist, and quartzite (|<sa) and carbonate rocks (|ca), undivided","Paleozoic and Proterozoic","","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8606","PzZss","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic?","Quartz-muscovite-graphite schist, calc schist, quartzofeldspathic schist, phyllite, and quartzite.  Unit is locally interlayered with unit |cs and is therefore, at least in part, Paleozoic in age.  Some of the unit may be as old as Proterozoic.  Samples of the schist yielded a metamorphic mineral K/Ar isotopic cooling age of 124 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000"
    "8610","Zc","Calc schist, quartz-mica schist, and greenstone","Proterozoic","Calc schist, thin bedded schistose impure marble, and fine-grained massive sandy marble.  Contains subordinate quartz-mica schist and small bodies of greenstone.  Unit underlies unit Ont and gradationally overlies unit Zs","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8625","PzZsr","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic?","Quartz-mica schist, chlorite schist, quartzofeldspathic schist, quartzite, and micaeous and graphitic schist.  Regionally metamorphosed to greenschist-facies, but also locally includes high-pressure greenschist-blueschist-facies (distinguished by the presence of glaucophane) and amphibolite-facies (distinguished by the presence of sillimanite and kyanite).  Andalusite-cordierite hornfels and contact schist occur in broad bands around Cretaceous granitic bodies of units Kgr and Ksy.   Unit locally is interlayered with carbonate rocks of unit |cr and therefore is, at least in part, Paleozoic in age.  However, some of the unit may be as old as Proterozoic.  The regional metamorphism clearly pre-dates the widespread intrusion of the Early Cretaceous granitic bodies of units Kgr and Ksy.  Metamorphic minerals in this unit in the Nulato quadrangle yielded  K/Ar isotopic cooling ages of 134 and 136 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8640","Zs","Pelitic schist, quartzite, quartzo-feldspathic gneiss, and greenstone","Proterozoic","Chiefly pelitic and quartzose metasedimentary rocks of greenschist metamorphic facies.  Micaeous quartzite and quartz-chlorite schist grade into quartz-muscovite-biotite-garnet     schist.  Subordinate calc schist and marble.  Unit locally includes small bodies of greenstone and greenschist metabasite,  granitic gneiss,  and metamorphosed quartz porphyry.  Zircon fractions from two samples of metamorphosed quartz porphyry indicate a crystallization age of 1,26550 Ma.  Metamorphic minerals from the schist yield K/Ar isotopic cooling ages that range from 921 to 296 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8641","Zs","Pelitic schist, quartzite, quartzo-feldspathic gneiss, and greenstone","Proterozoic","Chiefly pelitic and quartzose metasedimentary rocks of greenschist metamorphic facies.  Micaeous quartzite and quartz-chlorite schist grade into quartz-muscovite-biotite-garnet     schist.  Subordinate calc schist and marble.  Unit locally includes small bodies of greenstone and greenschist metabasite,  granitic gneiss,  and metamorphosed quartz porphyry.  Zircon fractions from two samples of metamorphosed quartz porphyry indicate a crystallization age of 1,26550 Ma.  Metamorphic minerals from the schist yield K/Ar isotopic cooling ages that range from 921 to 296 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8700","Zv","Metavolcanic rocks","Late Proterozoic","Banded, fine-grained, foliated,  felsic volcanic  rocks. Chiefly porphyry composed of large phenocrysts of embayed quartz and plagioclase in a very fine-grained quartzo-feldspathic groundmass that has a distinct micaceous overprint.  Subordinate fine-grained quartzo-feldspathic rocks which probably represent recrystallized felsic flows and tuffs.  Zircon fractions from two samples of a foliated quartz porphyry flow give a crystallization age of approximately 850 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "8710","Ynqd","Metamorphic basement rocks of the Nixon Fork sequence, Meta-quartz diorite","middle Proterozoic?","Sheared metamorphosed porphyritic quartz diorite.  Contains biotite phenocrysts as large as 1 cm and numerous micro-veinlets of quartz (Silberman and others, 1979).  K-Ar age on biotite yielded an age of 921+/-25 Ma and muscovite from mylonite along border yielded 663+/-20 Ma (Silberman and others, 1979).  Intrudes quartz-mica schist of unit ZYnm in the southwest Ruby quadrangle.  Corresponds to unit pCm of Silberman and others (1979)","Wilson, F.H., Dover, J.H., Bradley, D.C., Weber, F.R., Bundtzen, T.K., and Haeussler, P.J., 1998, Geologic map of Central (Interior) Alaska:  U.S. Geological Survey Open-File Report 98-133, 3 sheets, scale 1:500,000, 63 p. pamphlet, 13 p. appendix."
    "8801","MzZkc","Complex of the Kokrines Hills ","Mesozoic to Proterozoic?","Undivided assemblage of: 1) biotite granite and  granite gneiss including augen gneiss, 2) quartzofeldspathic schist, quartzite, pelitic schist and amphibolite metamorphosed to upper amphibolite to lower granulite facies, and 3) marble and calc-silicate  rocks.   Field data are insufficient  to map separately  the complexly interrelated lithologic components of this unit.  The granite and granite  gneiss yielded a Cretaceous U/Pb isotopic zircon crystallization age of 118 Ma and Cretaceous K/Ar isotopic cooling ages of 110 to 120 Ma.  The schist, quartzite, and carbonate rocks probably are correlative with units PzZsr and Pzcr of Paleozoic and Proterozoic(?) age
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."
    "9325","PzZsr","Pelitic schist, calc schist, and quartzite","Paleozoic and Proterozoic?","Quartz-mica schist, chlorite schist, quartzofeldspathic schist, quartzite, and micaeous and graphitic schist.  Regionally metamorphosed to greenschist-facies, but also locally includes high-pressure greenschist-blueschist-facies (distinguished by the presence of glaucophane) and amphibolite-facies (distinguished by the presence of sillimanite and kyanite).  Andalusite-cordierite hornfels and contact schist occur in broad bands around Cretaceous granitic bodies of units Kgr and Ksy.   Unit locally is interlayered with carbonate rocks of unit |cr and therefore is, at least in part, Paleozoic in age.  However, some of the unit may be as old as Proterozoic.  The regional metamorphism clearly pre-dates the widespread intrusion of the Early Cretaceous granitic bodies of units Kgr and Ksy.  Metamorphic minerals in this unit in the Nulato quadrangle yielded  K/Ar isotopic cooling ages of 134 and 136 Ma
","Patton, W.W., Jr., Wilson, F.H., Labay, K.A., and Shew, Nora, in prep., Reconnaissance geologic map and digital data for the Yukon-Koyukuk basin, Alaska - (Integrated digital geologic map databases of the United States):  U.S. Geological Survey Scientific Investigations Series Map SIM-XXXX, scale 1:500,000."