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feldspar that developed in quartz-mka schist and gneiss near the contacts of the two ban& of atgen gneiss (pashed lines, lw. 2) might represent the begi~ing stages of the same phenomenon. The association of those clots with the narrow bands considered to be sills may indicate that intrusion of the augen gneiss sills, formation of porphyroblasts, and cataclasis were all closely related in tlme The perfect eye shape of most augen could be evidence Chat growth of porphyroblasts and modification of their shape by cataclasis was contemporaneous. Petrographic examination of the fine-grained augen gneiss in question, as well as study of the metamorphic textures of the catactasized rocks in the upland h general, indicate8 that cataclasis and neocrystallieatlon were closely linked. However, because the timing of regional roetamorphism and cetaclasis subsequent to intrusion of the augen gneiss (about 350 m.y. B.P. for the large body of augen gneiss) is still uncertain wit1 .lin about a 150-m.y. F i i 29.--Slabs of augen gnek from localities in Big Delta C-2 quadrangle. 4 ZXtt~oaugen gnelsq from thick sill at locality 1 (fig, 28). Note fracturing and cataclastic deformation of originally idiomorphic megamysts, and apparent rotation of some smaller megacrysts. Largest auge is 12 cm long. B Enigmatic fine-grained augen gneiss from locality 3Tlfig. 28). In outcrop, augen are more evenly spaced than in this sample. Diagonal-stacking alincment of augen, which h common in coarse-grained orthoaugen gnelss, may be evidence for porphyritic-sill protolith. Largest auge is 1.25 cm long. L-. interval (Aleinikoff and others, 19811, a genetia relation between intrusion of the augen gneiss prote lith and possible porphyroblastic formation of other augen gneiss layers is only speculative. The various layers at the localities described are examples of the textural end members in the por phyroclastic to possibly porphyroblastic origin of augen gneiss in the upland. The silt of augcn meiss, which is the first such inkusive layer that we have recognized, may be similar to other layers of augen gneiss whoso interlayering with metesedimentary mcks was pre- viously Interpreted to suggest a sedirrlentary proto- llth. The incipient clots of feldspar in pelitic rnetased- imentary rocks near the narruw bands of augen gneiss are evidence that the formation of feldspar porphyroblasts in metasedimentary rocks may be a plausible explanation for same augen gneiss layers, and the augen gneiss layer at the last locality described is n good example of the equivoeel textures of the I1grey" area between the two end members. REFERENCES Cl"l'%D Aleinikoff, J. N., Dusel-Bacon, Cynthia, Foster, H. F., and Futa, Kiyoto, 1981, Proterozofc zircon from rtugen gneiss, Yukon-Tanana Upland, east-central Alaska: Geology, v. 9, no. 10, p. 469473. Duel-Bacon, Cynthia, and Aleinikoff, J. N., 1980, Pro- terozoic cataclastic augen gneiss in ?he southeastern part of the Big Delta qua&angle, Yukon-Tanma Upland, east+enbal Alaska [abs.]: Geological Society of America Abstracts with Programs, v. 12, no. 3, p. 104-105. Holdaway, M. J., 1971, Stability of andalusite and the aluminum silicate phase dlagram: American Journalof Science, v. 271, no. 2, p. 97-131. Raceelemeot evidence fat tbe tectonic aZIhrfties of some amphibolites from the Pnbn-'I'anana Upland, eest+entral BLaslce Bg Cynthia -1-&eon Amphibolite occurs throughout the Yukon- Tanana Upland, interlayered with metasedim entary and metaigneous rocks of Precambrian(?) and Paleozolc age. There has been considerable speculation as to the orlgins of the various nmphibolite layers and their geologic significance. Amphibolite may result from: (I) Metamorphism of basic igneous rocks, (21 metamorphism of calcareous or dolomitic shele, or (3) metasomatism involving the exchange of significant amounts of nonvolatlIe constituents (Preto, 1970). On the bnsis of traceelement evidence obtained in the preliminary study reported here, basaltic protoliths are indic~ted for amphibolite of the Yukon-Tenana Uplmd. In the amphibolite-grade terrane of the southeastern part of the Big Delta quadrangle (area 7, fig. 231, amphalite is corn rnonly interlayered with quarl-zofeldspathic gneiss and schist that are near the margins of, and probably wallrock for, a batholith-size body of orthoaugen gneiss of Late Devonian-Early Mississippian age (Aleinikoff and others, 1981). Samples from amphibolite layers at thee different localities around the augen gneiss pluton were cllernicdy
analyzed to determine whether Immobile minor- and trace-element cantents might be diagrrostic of the origin of these layers. Table 10 lists locations and modal analyses of the three arnphibolite and two as* elated gneiss aarnples, and table 11 lists major-, minor- , and tmce-element deta. PeatrlPes aharacteristic of metasomattc amphlboUte (OrvUle, 1969, p. 84) are absent at the three localities sampled, and a metasotnatlc origin Is c6nsidered highly unlikely. Lithologic Illterlayerlng at the first locallty (sample 40176) suggests a volcanic origin for the arnphiboute layer. The sample is from a LO-m-thick Lager of amphibolite with mbor interlayered plagioelase-rich bands. Thin biotlte-rich layers occur at several levels in the amphibolite outcrop; these layers might represent thin sedimentary laminae deposited between hyeH of mafic tuff. Zircon uranium-lead systematics that indicate an inherited older (sedimentary?) component in thfs amphibolite sample (J. N. Aleinlkoff, written commm., 1981) are also compatible with a bedded-tuff pprotolith. A 10-mthick layer of homogeneous biotite-hornblende felsic gneiss (sample 4019A) containing flattened lenses of e more mafic composition overlies the amphibolite. Lenses, with 6 flattening ratio of about l:20, make up as much as 50 percent of the exposure In some layers but generally constitute only about 5 percent. The lenses appear to be monolithologic and may have originated as mdic Inclusions in a sillcic lav~ flow. A total of 1 rn of eugen gnetss (sample 4017C) of probable igneous orIgln is exposed beneath the sampled amphblite. The other two arnphlbollte amples were collected about 30 km northwest of sample 4017. Sample 40243 is from a concordant band of amphibolite, several tens of meters thick, that aecurs within an area of quartzofeldspathic gneiss and garnetif erous quaTtZ-mice schist near the north Contact of a large arthoaugen gneiss body. Sample 4026B was collected from an adjacent parallel ridge 2.5 krn to the south- west at a 1- to 2-m-thlck outcrop of amphiboute con- Wing 8 Pew thin Interlayered feldspathio bands. Pelitlc schist and biotite gneiss, as well as a thin layer of marble, crop out nearby on the ridge. Similm amphibolite occurs mound the margd'lns of a small foliated serpentbite body 2.5 and 3.5 km west of the localities of samples 4026B and 40245, respectively. Leake (1964, p. 247) stated that high Cr contents (about 250 ppm) are excessive for pellte4olomlte mixtures but are appropriate for orthoamphihlite. Thus, the 311-ppm Cr aontent of sample 40268 probably indicates m igneous origln. The Cr contents of the other two samples (195 and 180 ppm) are well within the range of values for basalt but are also within the highest part of the range of possible shalecarbonete mixtures (Evans and Leake, 1980, p. 357) and me, therefore, nondiagnostia. The TiOZ contents of We amphfbolites fall in the uppermost range for pellte-carbonate mixtures but low in the range for basalt (Evans and Leake, 1960, p. 356; Nockolds, 1954, p. 1021). Althaugh some peUte has Ti0 contents as high as about 2 weight percent, pellte gen&elly is appreciably poorer In Ti0 (avg 0.82 weight percent) (Evans and Leake, 1980). %an peUte Is diluted by rnfxture with dolomite, which is very poor in no2, the resultant mixture will be lower in no2. Thus, if the amphlhlite were of sedhnentary parentage,thesedlmentwasunusu titaniferous. The NiggU k value (Barth, 193, based primarily on the ratlo of K 0 to K20+Na20, wm considered by Evans and Leake h960, p. 356) to be greater then 0.50 In amphibolite derived from the metamorphism of mixtures of cky and dolomite. Although the k values for the am Mbollte samples of this study are considerably lower f 0.09, 0.14, and 0.18 for samples 40245, 40268, and 40178, respectively) and thus might be used as Table 10.--Mdal anal ses of a hibollte and associated nelss sa les from the 9 - 4 e ~ t + e ~ u k o n - 1ana.a &EFT--- CAI 1 modes Ih volme percent, based on 1.500 data potnts. Sample 4417A was inclusion free. tr, trace1 Amphibol t te Gnel ss $amptea-------- ---- L---=-- 402Q 40268 40178 401 7A 401 7C lat. N-------------------- 64'23' 11" 64'22'34" M008'40" 64°08'40" 64'08'40" Long. W------------------- 144'37'52" 144'41 '18" 144'26 '30' 144'26 '30" 144'26'30" Quartz--.mz------=-------- Pl agfoc~as~--------i----- K-fe) dspar-----. ------ ---- BfOtj-te ---- =. --------- ---- Wh{te mfca-a--~--------a.-nctfnol ltse hornblende---- Chlorite--.--------------- Epldot*--c--------------.. cl {nozoisite ---- ---------- Cltnopyroxenc------------ Sphene-----------.---.---A Apatfte-----l--cd--------- A\lan
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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 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: ecrSigtallized catadastic matrix of
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
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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
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epizonb'l granitic Miss, mixed with
Page 133 and 134:
40 40 Forbes, R. B., and Engels, J.
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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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