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EXPLANATION Cretaceous and Jurassic sedimentary rocks hmq Triasslc, Permian, and Carboniferous sedimentary mcks 1 Dhk I Upper Devonian sedimentary rocks-Hunt Fork Shale and Kanayut Conglomerate 1-1 ..... Devonian sedimentary rocks older than the Hunt Fork Shale Ordovlclan or Cambrian sedimentary mckr Volcanic rocks PI Mount Doonerak Ouartz-mica and calcareous schists ml Granite Contact -I--L Thrust fault; dotted where inferred F9gma 9.-43eneraHzed geologic and structuntt map of Mount Daonera~; r, ralsooh Mountain; SS, Woyuk Doonerak anticlinorium and adjacent areas. X, synclinorium; W, Wiseman; WL, Wild Lake (from Dutro loeation of trilobite bedst A, Anaktuvuk Pass; C, end others, 1976, fig. 1). Chandler Leke; DA, axis of Doonerak anticllnoriurn; Dl
who found Westeqaardodina sp., posble hyouthids, and undetermined accotretid brachiopods. Other samples, from two localities in the gray mwble bodleg, contain microfossils that, according to Repetski, elso include Westergaarddlna sp., a paraconodont which ranges in age fmm Middle Cambrian into Early Ordovician in many parts of the world. It is now clear why we were unable to flnd gap- tolites in this sequence: it is probably entirely Cambrian. The marble bodies and asscxlIated beds provide a key to the geologic mapplng of these old rocks. The brown Limestone and gray marble are found as far west as Tobh Creek, on the west-plunging nape of the anti- clinorlurn, where they are fsocllnatly folded within the clastic sequence and intrudd by greenstone dikes. Thus, part of the mystery of Doonerak has been solved. Its Cambrian rmks can be correlated with those of the northeastern Brooks Range (Dutro and others, lQ72) and may be related to the Arctic Cam- brian sequences in Siberia, Hllesmerehd, North Greenland, and other parts of the North Atlantic Caledonides. These are the oldest fmiliferous rocks thus far dkcovered in the central or western Brooks Range. Further sesrch in the probable southwestward exten- I sion of this structural trend should turn up additional discoveries. The search goes on. REFERENCES CITED Brosg6,W. P. and Reiser, H. N., 1971, Prellmjnary bed- rock geologic map, Wiseman and eastern Survey Pass quadrangles, Alaska: O.S. Geological Survey open-file map, scale 1:250,000, 2 sheets. Dutro, J. T., Jr., BmsgC,W. P., and Reiser, H. N., 1972, Significance of recently discovered Cambrian fossils and rehterpretation of NeruoQuk Porma- tion, northeastern Aleska: American Association of Petroleum Geologists Bulletin, v. 56, no. 4, p. 808-815. Dutro, J. T., Jr., Brosg6, W. P., Lanphere, M. A., and Reiser, H. N., 1976, Geologic significance of Doonerak structural high, central books Renge, Alaska: Amerlcan Association of Petroleum Geologists Bulletin, v. 60, no. 6, p. 952-961. Rdser, H. N., hg6, W. P., Dutro, J. T., Jr., and Detterman, R. L., 1971, Preltminary geologic map, M t. Michelson quadrangle, Alaska: U.S. Geological Survey open-file map, scale lr200,000, 2 sheets. Reiser, H. N., Brosgd, W. P., Dutro, J. T., Jr., and Dettermm, R L., 1980, Geologic map of the Demarcation Point quadrangle, Alaska: U. S. Geological Survey Miscellaneous Investigation Series Map 1-1133, scale 1:250,000. Geothermal studies in Alaslra: Ccmditlomr at Prudboe sas roents in Alaska as opportunities wlse in holes drilled for other purposes. Ow objective L a htter under standing of the tectonics and geothermaknecgy resources, and of the geothermal regime of permafrost. This year, we completed e study of the thermal reglrne in the Prudhoe Bay area on the coast of the Beaufort Sea (area 5 of fig. 51, on the basis of temperature measurements through permafrost In the Rudhoe Bay oilfield that we obtained through the cooperation of BP Alaska, Inc., and the Atlantic Richfield Oil Co. An analysh of these data, and of thermalconductivity measuremenis on samples of drill cuttings and frozen core, leads to the following concIusions (~achenbruch and Marshall, 18771 Lachenbruch and others, 1983): 1. The heat flow from the Earth% inbrio5 is 1.33.2 heat-flow units (HPU) (55k8 mW/m 1, a value Wta of stable eontlnental regions, similar to the values measured at Cape Thompson (Lachenbruch and others, 1966) and estimated at Barrow (Lachenbruch and &ewer, 1950). 2. me permafrost on land near Prudhoe Bay extends to a depth of 630+ m, 50 to 100 percent deeper than permafrost in the mow area. This greater depth is caused by the high thermal conductivity of the coarse ice-rich siliceous sediment in the Prudhoe Bey area; only a small thermal gradient is required to transport the heat flowing from the Earth's interior throwh such conductive material. As 8t other sites along the Arctic Alaskan the mean annual temperature of the Wth's surfaoe has Increased sharply in the pest hundred years. In the Prudhoe Bay area, we estimate that this increase averages about 1.8'~ (from -10.9' to -9.1'~) and that it is aesoeiated with a net accumulation of 5 to 6 kcal/cm by the Earth's surfaoe during this perid. Rlsing sea levfil (Hopkins, 1983) and thawing seacuffs (Barnes and others, 1977) pmbably caused the shoreline to advance tern of kilometers in the past 20,000 years, so that a part of the Continental Shell Ulat is presently the target of intensive oil exploration was inundated. A simple heat-conduction mbdel suggests that the warm seabed wlll cause the base of Icerich permafrost to rise about 10 m (from 600f m) during the first 2,000 years efter inundation, and thereafter it will rise about 15 m per 1,000 years. Accordingly, this recently Inundated region k probably underlain by near-melting Lcerich permafrost to depths of 300 to 500 m; its presence is important to seismic interpretations in oil exploration and to engheering considerations in 011 production. With confirmation of the permafrost configuration by offshore drilling, conduction models can yield reliable new Wor mation on the chronology of Arctic shorelines. REFBFLENCES CITED Bg Arthur a- Lacbedmlch, John H. Sasq R Vtulghn MmhaU, 'lhornas H. M-, Jr., Robett J. Munroe,and Barnes, Peter, Reirnnitz, Erk, Smith, Oreg, and m e P. Smith Melchior, John, 1977, Bathymetric and shoreline changes, northwestern Prudhoe Bay, Alaska: The U.S. Geological Survey% Geothermal Studies U.S. Geological Survey Open-Pile Report 77-161, Project is contfnuing to obtafn heat-flow measure- 10 p. -
Page 1 and 2: n Alas Accompli: ' I.S. GE OLOGI CA
Page 3 and 4: I CONTENTS Page A bst raet ........
Page 5 and 6: -- --A I ALASEU i nued rral expluru
Page 7 and 8: ........ igure .JB. ;5~ercn map ox
Page 9 and 10: . , ".,k a. ,.e ,\a 1 y U11 IIIUUII
Page 11: THE UNITED STATES GEOLOGICAL SURVEY
Page 15 and 16: ~ t I r n t S i m ~ ~ Alarr a ~ man
Page 17 and 18: I -1977, RelImlnary documentat!on l
Page 19 and 20: 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: I that contains the Upper Devonian
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 and 72: westward into a narrow band that ex
Page 73 and 74: EXF'lANATIOW 66600' Contan-Apprnimn
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
Page 123 and 124:
marble is alsa locally present In t
Page 125 and 126:
Bedding in the conglomerate ranges
Page 127 and 128:
1 purpose of this study wes to dete
Page 129 and 130:
The secona k~~-~ri?tation mmes that
Page 131 and 132:
epizonb'l granitic Miss, mixed with
Page 133 and 134:
40 40 Forbes, R. B., and Engels, J.
Page 135 and 136:
foliated and inequigranular end con
Page 137 and 138:
I I thy euheclra. Sphene anhedra an
Page 139 and 140:
Quartz Alkali feldspar Plagioclase
Page 141 and 142:
F'@m 85.--Sketch map of Juneau area
Page 143 and 144:
HoUister, L. 8, 1966, Garnet zoning
Page 145 and 146:
! ~ bI8oO, (IN PERMIL) ~lqp~e 87.-8
Page 147 and 148:
Figure 90.-Offshore ereas discussed
Page 149 and 150:
Preliminerg analpsis of miemfauna f
Page 151 and 152:
Survey tn Alaekai AccompUshments hh
Page 153 and 154:
Gecllogical Survey Open-File Report
Page 155 and 156:
I provenance, and tectonia sIgnific
Page 157 and 158:
Keith, T. E. C, Barnes, Ivan, afrd
Page 159 and 160:
Open-Flle Report 8P811C, 19 p. + 2
Page 161 and 162:
United States Qeological Survey in
Page 163 and 164:
, ,. nldslra poblisbe!d by Prior, D
Page 165 and 166:
60, Alaska: Offshore Technology Con
Page 167:
Author Index [Page number underscor
Page 170 and 171:
Parks. Bruce ......................
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