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Cretaceous time. Similarly, the wport of low palsolatitudes (approx 20') from the Nutzoth Mountains sequence of the Gravina-Nuteotin belt (Packer 'and Stone, 1974; Stone and others, 1982) dews the wibility that these terranm did not accrete to North America until post-&ly Cretaceous time. However, this conclusion is contrary to the interpretation of Hillhouse and ~romm6(l980) besed on a more complete paleornagnetic study of the Hound Island Volcanics. l'heir daEa suggest that the Alexander terrane has not moved northwad rehtive to cratonal North America slnoa before Late Triassic time. This conflict could be resolved by accepting the reversed (Southern Hemisphere) polarity of the Hound Island Volcanics as the correct magnetic direction (Stone and others, 1982). Table 20.--?alemagnetic data of selected Gravina-Nutzotln belt rocks on Marsh Island [Sratlgraphlc declination (0) and inclination (1) of vector corrected for tllt of bedding, in degrees. A.F., peak a1 ternattng-f ield intensf ty'J Bed Stmtfgraphlc Dema9nei1za'i0n A.F. D I temperature ('C) lrnT) ,mu/cm3) Intensf ty (lo-b Comments 500 -- 2.26 --- 450 - - 4.17 --- 500 - - 4.33 --- 450 -- 8 .Ol --- 450 -- 4.15 ..-- 450 -- 10.1 --- 450 - - 9.66 .-- 500 -- 5.25 --- 400 -- 2.92 --- 500 -- 7.41 --- 500 -- 3.13 --- 500 -- 2.47 --- 550 -- 26.5 Remagneti zed by dtke. 600 -- 2.02 --- 506 -- 3.09 --- --- 10 5.35 --- --- 10 4.78 --- - - - 20 4.05 --- --- 5 7.91 --- --- lo 5.73 - -- --- lo 6.01 --- --- 10 7.18 --- --- 30 5 -09 - -- - -- 10 8.00 --- --- 10 6.49 --- Table 21.--~paleomagnetic data on four Gravlna-Nutotln belt beds on Marsh Island [Geographic dectlnatlon ID) and lncllnatian (1) of onslte vector directfon with respect to present north and horizontal. Stratlgraphlc declinatfon (0) and fncl Ination (I) of vector corrected for tllt of beddlng. K, Fisher's prectston parameter; a , radius of 95-percent-conffdence clrcle; VG~, virtual geomagnetk pole. All d??ectional and VGP values In degrees) Nmber hographi Strattgraphfc VGP Bed of samples D I Long- leti- D l - '95 ltvde tude - a95 - - 3 4 129 71 54 16 260.4 4.3 344 26 775.9 2.5 4 2 113 63 61 9 79.1 11.1 340 20 84.1 10.8 Mean of 4 beds-- 143 70 56 20 04.9 10.5 342 28 86.5 7.5
The secona k~~-~ri?tation mmes that the mean Stone, D. B., Pmuska, B. C., and Packer, D. R., 2982, magnetic vector obtained from the Mash Island Palmlatitude versus time for southern aka: samples represents thermal remanent megnetizatIon Journal of Geophysical Research, v. 87, no. 5, p. acquired during an unknown postdeposltlond thermal 3897-3707. event. Unpublished paleornegnetic data (C. S. ~romrnd and J. W. Hillhouse, oral commun., 1982) from northern Prince of Wales Island, Etolin khd, and the lBe mrihem Gxiat m-etsrnme mmpw I Screen Islands, indicate mwetic vectors, uncorrected for tectonic tilt, that point steeply downward to the southeast, similar to the Marsh Island directions. The important points are that: (1) The localities which Grommb and Hillhouse sampled surround the Marsh bland locality (fig. 781, and (2) rocks of different ages and varying bedding attitudes aU show the same anomalous magnetic direction. When corrected for tectonic tilt, the Marsh Lsland, Prince of Wales Ishnd, Etolin Island, and Screen Islands vectors diverge from their common down-to-thesoutheast orlentatlon and thus, taken together, fail the fold test. The obvious conclusion k that a regional post-Albian w- Abka and mxth~e~tem MtS8h Columbia SJI David & mDd Artb~W Ford INTRODUCTION The northern Caast plutonicmetamorphic complex is but one Segment of an 8,000-km-long batholithic complex that extee the length of the North American Cordillera from Baja Californit3 to the Aleutian Wands. As described here, the northern Coast plutonic-metamorphi complex (area 1, fig. .72) remagnetization affected all the above sample sites. lies between lat 55O and 60 N. The adjacent segment I However, the steep down-to-thesoutheast direction to the north has been described only in reparts 1 does not correspond to any known or suspected post- concerned with regional gmlw (Kindle, 1953; Muller, I Abian geomagnetic field, assuming that the sample 1954, 1967; Christie, 1957; Wheeler, 1861, 1963; sites have been in their present orientation and at Campbell and Dcdds, 1975, 1878, 1979); the adjacent their present latitude since Alblan time. Therefore, if segment to the south was described by Hutchison post-Albian regional remagnetization in southeastern (1970) and Wick and Hutchison (1974) as well as .- Alaska is to be assumed, additional depicted on various regional geologic maps. postremagnetization regional tilting, rotation, and (or) Different segments of the Cordilleran batholithic translation is required to establish the necessary complex have significantly different festlwrr. 7bb correspondence between known geomagnetic-field report documents the main cheracteristlcs and directions and the measured sample directions. inferred evolutionary history of the northern Coast In summary, our data indicate that the dikes that plutonic-metamorphic complex that should facilitate cut the Narsh Island section of the Gravlna-Nutzotin comparisons between segments. belt did not remagnetize these beda, and 60 the beds The Coast plut onicmetamorphic complex is pess the baked-contact test. Nonetheleas, we cannot defined here more or less according to the usage of 1 rule out the possibility of regional remagnetization. Douglas end others (1970) and Brew (1981) but not that Further mmplfng is required to distinguish between the of Brew and Ford (1978). Thus, the northern Coast two interpretations for the origin of the magnetization plutonic-metamorphic complex includes not only the I described above. dominantly granitic and gneissic rocks of the Coast Mountains, bui also the mebrnorphic rooks adjacent to REFERENCES CTTBD both sides This definition poses no problems so far as the northeast limlt of the complex is concerned Berg, H. C., Jones, D. L, and Richter, D. H., 1972, because there the outer contact of the low-pressure Gravina-Nutzotin belt-tectonic significanoe of facles-serles metamorphic rocks adjoining the an Upper Mesozoic sedimentary and volcanic northeasternmost plutbns is relatively clear. sequence in southern and southeastern Alaska, The southwest Iimit of the northern Coast Geological Survey resesrch 1972: U.S. plutonic-metamorphic complex, however, is difficult Geological Survey Professional Paper 800-D, p. to place because the mediumgressure f'aciesseries Dl-D24. metamorphic rocks that contact the granitic and Hillhouse, J. W., and ~rornrni, C. S., 1980, gnelssic rmks of the northern Coast plutonic- Paleornagnetism of the Wassic Hound lshd metamorphic complex decrease in grade to the Volcanics, Alexander terrane, southeastern southwest and appear to form a single wide Alaska: Journal of Geophysical Research, v. 85, metamorphic and deformation belt. As noted below, no. B5, p. 2594-2602. there may, instead, be two bells of different ages side Irving, Bdward, and R.tliaiah, Ountur, 1976, Reversals by slde. Figure 79 shows this wide area of medium- of the geomagnetic field, rnagnetostratigraphy, pressure low- to medium-temperature rnetarnorphlsm and relative magnitude of paleosecular varfatian a9 the informally named western metamorphic zone; it in the Phanemzoic: Earth-Science Reviews, v. haa as its southwest Emit the southwesternmost 12, no. 1, p. 35-64. contacts of flysch units within the U per Jurassic(?) to McBUinny, M. W., 1913, P&eornmetism and plate middle Cretctcecus Oravina belt &erg and others, tectonics: London, Cambridge Unjversity Presf, 1978). The reason for selecting thb boundary is 358 p. twofold: (1) The generally low grade metamorphism in Packer, D. R, and Stone, D. B., 1974, Paleornegnetism these units appears to grade northeastward into the of Jurassic rocks from southern Alaska and their higher grade metamorphism in the granitic and tectonic implications: Canadian Journal of earth gneissic rocks of the northern Coast plutonic- Science, v. 11, no. 7, p. 976-997. metamorpMc complex; and (2) the deformational 120 8 ,
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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
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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
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were deslgned to impMve the accurac
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Noatak Sandstom and is overlaln con
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I (Nilsen and others, 1981a); (2) f
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I that contains the Upper Devonian
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who found Westeqaardodina sp., posb
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Table 2 lists the means rtnd for th
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' Noatak Vdley (fig. 129. This ice
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3 EUMN OF MAP UNITS WAmWARY OUAERNA
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-om displacement of the cc tween th
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I US I Surlicial dcnrrua,ts [~dater
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I Plafker, George, Hudson, Travis,
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!omlensed iring vapors generated by
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and the thinning. -upward cycles .,
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Kellum, L. B., Devless, S. N., and
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1912 sample (a mediumwey pumice blo
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various Utholagic units present Thu
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fault, and Its depositional basemen
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suggested by coplanar foUaticm and
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1 slgnlficarrtly more umnlum (73&1,
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ecrSigtallized catadastic matrix of
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analyzed to determine whether Immob
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are tgplcd of both ocean-floor basa
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& Fclsic in~rutirt rucks 0 Eio~ite
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are Lrdlcated by coexisting @&ite+q
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(Mg3.09 pe2+ 0.69 pe 0.~1~0.01~~0.9
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westward into a narrow band that ex
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EXF'lANATIOW 66600' Contan-Apprnimn
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! 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: 1 purpose of this study wes to dete
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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