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More detatied geologic mapping, stratigraphic In the central pnrt of the eastern Crazy Mounwork, and fossil collecting must be done before tire tains, radiolarian chert occurs in e 1.5-km-wide puzzling stratigraphy and structure me unraveled, but easterly trending band that lies north of acenite, argila start has been made in deciphering the complex geo- lite, and black arenaceous limestone of Cambrian(?) logic relations in the Crazy Mountains. age (fig. 38, area A). Although black chert appears to be the domlnant rock type in this band, the radiolar- REFERENCES CmD lans are found in intertayered gray chert. Locally the chert is finely banded, light and medium gray and Brabb, E. E., 1967, Stratigraphy of the Cambrian and black; gray arglllite occurs in at least one locality. At Ordovician racks of east-eentral Alaska: U.S. the westernmost radiolarlan locality (80AWr91C) in Geological Survey Professional Paper 559-A, p. this band, the fossils are Albaillella sp. (an undescribed AI-A30. Late Mimisippian species) and ParonaeUa impella Churhc, Michael, Jr., and Brabb, E. E., 1965, Occur- Ormiston and Lane, which are considered Late Missisrence and stratigraphic significance of Oldhamia, sippian. At a second locality to the east (80~~r272) a Cambrian trace fossil, in east-central Alaska, the chert contains tFipongodiscaceid gen. nov. (tetrain Geological Survey research 1965: U.S. Geo- hedral)" (LToldsworth and Jones, 1980), which is con- Kgical Survey Professional Paper 525-D, p. sidered to be latest Late Mississippian or Urly Pem- D120-D124. sylvdan. Two other localities (80~Fr2084, Mertie, J. B., Jr., 1937, The Yukod-Tanana region, 80~~~279A) in this band yield very poorly preserved Alaska: U.S. Geological Survey Bulletin 872, 276 Spumellmiina, the age of which is uncertain, but may P. be Carboniferous. These rediolarians help define this Oliver, W. A., Jr., Merrfam, C. W., and Churkin, band of Carboniferous(?) chert, which appears to lie Michael, Jr., 1975, Ordovician, Silurian, end beyond the south boundary of mafic intrusive and vol- Devonian corals of Alaska: U.S. Ueologicd canic mks comprising the Circle Volcanics. Because Survey Professional Paper 823-8, p. 13-44. of poor expasures and covered contacts, the relation of these chert units to the Clrcle Volcanics to the north Late 1s and eatb Ywmie rad,O- ~ not known, although they may be part of the Circle Volcanics. A thrust fault is postulated to separate this Csrele qdmngle, ewit-adral Alaska Carboniferous(?) chert unit from the lower Paleozoic sedimentary rocks farther to €he south. By FIeh L. Poster, Grant W. Ctlshtrrg, Plotedce R To the north of the band of Carboniferous(?) Weber9 David D. Home L- Mw* Cbea rocks just described, chart is found in contact with gabbro and basalt (Circle Volcanics). The radiolarians in these rocks (lacs. 7, 8, fig. 38, Area A) are not yet Late Paleozoic and early Mesozoic radiolarims described but are recognized as Late Triassic. have been found in slightly metamorphosed chert north In the Little Crazy Mountains, basalt and gabbro of the Tintina fault system in the Circle quadrangle similar to that of the eastern Crazy Mountains has (area 8, fig. 23). During the course of reconnaissance minor amounts of chert in contact with it. Most of the geologic mapping, 32 chert samples were collected. chert layers ere thin and discontinuous. The color fs Subsequently processed to determine their radiolarian donr~tly gay, but red and black chert also are content, 11 samples yielded radiolarians whose age found; the gray chert commonly weathers white or could be determined, and 16 other samples contained very light gray. In the eastern part of the Little Crazy radiolarians that were either nondiegnostic or too Mountains, rediolarians were found in a saquence of poorly preserved for identification. Most of the gray and bleached white ribbon chert, wlth layers of samples containing identified radiolariana, which were chert ranging From 2 to 18 cm in thickness but averfrom areas mapped as the Ckcle Volcdcs (Mertie, aging about 5 crn. A section of about 2.5 m of chert is 1937) in the northern part of the eastern Crazy and exposed here, and the outcrop is about 170 m long, the Little Crazy Mountains, Indicate that these rocks largest outcrop of chert seen in the Little Crazy include chert of two distinct ages-Late Mississippian Mountains. Chert collected from the top of the or Early Pennyslvanian, and Middle and Late Triassic. sequence (Ioc. 9, sample number 01APr223D) contains Thus, the age of the Cirole VolcaniCS is here Paronaella impella Ormiston and Lane, Albaillella sp., considered to be late Paleozoic and Triassic. and Spon otri us sp; the chert at the base of the Radiolarlars were identified from chert sam~la sequence 2.6 m below Ooc. 9, sample number assaciated with mafic igneous rocks included in the 81AFr223E) contains Paronadla Impella Ormiston and Circle Volcanics (Mertie, 1937). These ~Eimples are Lane. These radiolarians indicate that chert of this from several localities on the Yukon River, in the outcrop is most likely Late Mississippian. eastern Craay Mountains, and in the Little Crazy A chert outcrop (loc. 10) about A kjlorneter West Mountains (fig. 38). Along the east bank of the Yukon of loc&tg 9 (fig. 38, Area A) contains Ca nodoce sp. River in the Circle C-1 quadrangle (locs. 1, 2, fig. 38, aff. C, anapetes DeWever, Capnodoce sp., + . Canopturn Area A), the radiohian chert is interlayered with sp., and Quasipetasesp,. which indicate a Late Triasfinegrained basalt. Underlying the basalt and chert is sic (late Karnien to Middle Norim) age. Chert jn the a sequence of layered gabbro wlth alternating plegio- eastern part of the Little Crazy Mountains 12 krn to clase-rich and plegioclase-poor layers. The ohert con- the east Qoc. 81 AFr 2280) contains ? Archaeospongotained wSpongodlscaceid gen. nov. (tetrahedral)" prunum iaponicurn Nabaseko and N ishirnur a, Triasso- (Holdsworth and Jones, 1980) md "Parahagiastriids" campe sp., and other undescribed spurnellariinids. A (Holdsworth and Jones, 19801, which indicate a latest Middle Magsic (Ladhian) and kite 'l'rimic (early Mississippian or Early Pennsylvanian age. Karnian) age is indicated for this chert. 62
EXF'lANATIOW 66600' Contan-Apprnimnmty bFatd 85.45' 145'30' 145@00' S~~HFCI daparn - A* - - Fauft rocks -L--L-L Thn~si lault . Sawleofh on qppn @ate Praomrc~ und,n*sntlatsd Western Crazy Mountains bole locallty - A- - Eastern Crazy Moutains SurCil cbposltf II~SIW am s~ttrmn LBCIUrrt WITH ~AbloURlANS 1. 80AFr 20698 7. BOAFr 242 2.80AFr 2070A 8. 80AFr 172 3, 80AWr 9lC 9. 81AFf 2230,E 4.80AWr 272 10. B1AR 211 5. BOAR 2084 11.0lAR 2288 6. BOAWr 2791 12. (IIAWf 236C R 13.81AFr 2960 fW&taru pmml In chsn. but nor drapnosfrc a mrfy prasewed Circle quadrangle Figure 38.--Geologic maps showing radlolarian-chert localities in two areas In northern part of the Cirde quadrangle. 'Thus, the Crazy Mountains and the Little Crazy Mounldns have chert bearing both MtssIsstppian and Triassic radiolarians. The chert units of both ages me similar in appearance and in thefr relation to the basalt and gabbro with which they are associated; end the igneous rocks, though as yet little studied, do not display any easily observable lithologic differences, and radiometric-age determinations lor them are unavailable. At present, the two chert units and releted mafic igneous rocks within the Circle Volcanics are not separately mappable. Nondiagnostic radiolerians were found in the ~brt in the Circle C-4 quadrangle south of the Crazy antains (lm. 12, sample number 81AWr236C, fig. , Area B). The common occurrence of some of the ?scribed spurnellariinids in this sample in MIssisslp- ,-XI chert suggests a Mississippian age for these. A second locality (loc. 13, sample number 81AFr296D) 2 km to the southwest of locality 12 has only nondlag- nostic poorly preserved spumellmiinids. ?Ais chert is also associated with rnafic igneous rock and 8 complex section of sedimentary rocks (Poster and others, 1983). Radiolarim that are either nondlagnostjc or too poorly Qprserved to identHy are aka found In three localities in the southern part of the eastern Crazy Mountains, at five localities in the western Cmzy Mountalns, and at two locallties in the Clrcle D-6 quadrangle. Because of the sawcity of fmih in the Circle quadrangle, identification of radiolarians from chert is of major significance in deciphering the geologic rela- tlons and history, pwtjcular1y of the Crazy Mounlains and LitUe Crazy Mountains areas. The radiolariens from the CIrcle Volcanics along the Yukon River and in the tittle Crazy Mountalns Indicate a terrane that Lncludes at least two widely separated times of chert deposition-late Mississippian or Early Pennsylvdan, and Middle and Late Triassic. Because these two groups af chert units within the Circle Volcanics and thelr associated igneous rocks cannot presently be d is tingutshed from each other in the field and the relation of the Carbonlferoua(?) chert unit to the south is not known, the geology and history of this terrane require addit lonal study. REFERENCES CITED Poster, H. L., Weber, F. R., and Dutro, J. T., Jr., 1983, Paleozoic Limeslones of the Crazy Moun- tolns and vicinity, Circle quadrangle,
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n Alas Accompli: ' I.S. GE OLOGI CA
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I CONTENTS Page A bst raet ........
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-- --A I ALASEU i nued rral expluru
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........ igure .JB. ;5~ercn map ox
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. , ".,k a. ,.e ,\a 1 y U11 IIIUUII
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THE UNITED STATES GEOLOGICAL SURVEY
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~ t I r n t S i m ~ ~ Alarr a ~ man
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I -1977, RelImlnary documentat!on l
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I I MaCenn, W. R., Perez, 0. J., an
Page 21 and 22: were deslgned to impMve the accurac
Page 23 and 24: Noatak Sandstom and is overlaln con
Page 25 and 26: I (Nilsen and others, 1981a); (2) f
Page 27 and 28: I that contains the Upper Devonian
Page 29 and 30: who found Westeqaardodina sp., posb
Page 31 and 32: Table 2 lists the means rtnd for th
Page 33 and 34: ' Noatak Vdley (fig. 129. This ice
Page 35 and 36: 3 EUMN OF MAP UNITS WAmWARY OUAERNA
Page 37 and 38: -om displacement of the cc tween th
Page 39 and 40: I US I Surlicial dcnrrua,ts [~dater
Page 41 and 42: I Plafker, George, Hudson, Travis,
Page 43 and 44: !omlensed iring vapors generated by
Page 45 and 46: and the thinning. -upward cycles .,
Page 47 and 48: Kellum, L. B., Devless, S. N., and
Page 49 and 50: 1912 sample (a mediumwey pumice blo
Page 51 and 52: various Utholagic units present Thu
Page 53 and 54: fault, and Its depositional basemen
Page 55 and 56: suggested by coplanar foUaticm and
Page 57 and 58: 1 slgnlficarrtly more umnlum (73&1,
Page 59 and 60: ecrSigtallized catadastic matrix of
Page 61 and 62: analyzed to determine whether Immob
Page 63 and 64: are tgplcd of both ocean-floor basa
Page 65 and 66: & Fclsic in~rutirt rucks 0 Eio~ite
Page 67 and 68: are Lrdlcated by coexisting @&ite+q
Page 69 and 70: (Mg3.09 pe2+ 0.69 pe 0.~1~0.01~~0.9
Page 71: westward into a narrow band that ex
Page 75 and 76: ! few fold closures are preserved.
Page 77 and 78: even thickness and conform to irreg
Page 79 and 80: (Alnus ap.), heaths (Ericaceae, + E
Page 81 and 82: terrane extends at least 300 krn to
Page 83 and 84: Table 19.--6tneral petrography of M
Page 85 and 86: were measured on 8 12-in. mass spec
Page 87 and 88: Thin lenses of cabonate packtone to
Page 89 and 90: The cantwell(?) Pormation south of
Page 91 and 92: in the 18 lava flows b thermoremane
Page 93 and 94: Upper Cretaceous shale in contact w
Page 95 and 96: Gran tz, Arthur, 1960, Generalized
Page 97 and 98: at 15 to 20 percent. Primary Inolus
Page 99 and 100: addition, this factor generally def
Page 101 and 102: Joreskog, K. G., Klovan, J. E., and
Page 103 and 104: Mineral qItWation end r ~ k t k W e
Page 105 and 106: 1 "~_liO-/ 200 1000 B roo C E % A B
Page 107 and 108: Smaller placer mines ere active on
Page 109 and 110: Figme 62.-Plant fassils from the co
Page 111 and 112: Hallam, Anthony, 1975, Alfred Wegen
Page 113 and 114: u ALASKA Figure 65.--Sketch map of
Page 115 and 116: F ' i a?.-Intertidal bluffs compose
Page 117 and 118: C-s - - Figure 70.-Products of eros
Page 119 and 120: curve is based indicates that 6.1 c
Page 121 and 122: sampled is related to widespread ma
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marble is alsa locally present In t
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Bedding in the conglomerate ranges
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1 purpose of this study wes to dete
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The secona k~~-~ri?tation mmes that
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epizonb'l granitic Miss, mixed with
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40 40 Forbes, R. B., and Engels, J.
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foliated and inequigranular end con
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I I thy euheclra. Sphene anhedra an
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Quartz Alkali feldspar Plagioclase
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F'@m 85.--Sketch map of Juneau area
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HoUister, L. 8, 1966, Garnet zoning
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! ~ bI8oO, (IN PERMIL) ~lqp~e 87.-8
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Figure 90.-Offshore ereas discussed
Page 149 and 150:
Preliminerg analpsis of miemfauna f
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Survey tn Alaekai AccompUshments hh
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Gecllogical Survey Open-File Report
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I provenance, and tectonia sIgnific
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Keith, T. E. C, Barnes, Ivan, afrd
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Open-Flle Report 8P811C, 19 p. + 2
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United States Qeological Survey in
Page 163 and 164:
, ,. nldslra poblisbe!d by Prior, D
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60, Alaska: Offshore Technology Con
Page 167:
Author Index [Page number underscor
Page 170 and 171:
Parks. Bruce ......................
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