n Alas - Alaska Division of Geological & Geophysical Surveys - State ...

More documents

Recommendations

Info

Figwe 68.-Planar and convoluted bedding in sedlment exposed in intertidal bluff. Dashed lines are along discontinuities within contorted sequence. deformed deposits neer Anchorage, however, extend I into the active tidal zone, where ice loading does not I OCCLIT. Swift silt-laden high-dendty currents and rapidly changing water levels in a macrotidal environment, such AS the regimc of upper Cook Inlet, may create frictional drag on the cohesive but saturated surface sediment and cause Liquefaction and soft-sediment deformation. The resulting features have been docu- mented in other macrotidal settings (Bay of Fundy; Delrymple, 19791, but they ere on n smaller scale and have e l qer proportion of undisturbed sequences than those observed neor Anchorage. P w 69.-Planar-bedded sequence truncating an underlying convoluted sequence. Channel undercutting can result in landsliding and slumping of unsupported deposits and creation of bluffs like those under study. Charnel development could cause an increase in the surface slope of the deposit that may, in turn, cause instabiUty In the saturated sediment and "creepn of the sediment channelward, with the attendant develop~nent of con- tor ted bedding. Small-scnled convoluted beds, similar to those seen nenr Anchorage, have been observed ad- jaoent to channels in the present-dny Intertidal silt at Portage, about 80 km southeast of the study area (fig. 66.9, but we were unAble to detect the presence of channels in the deposits at Anchorage or Portage. The channels may be destroyed by slumping. REFERENCES CiTED Dalrymple, R. W., 1979, Wave induced liquefuction; a modern example from the Bay of Fundy: Sedi- mentology, v. 26, no. 6, p. 835-844. Hansen, W. R., 1966, Effects of the earthquake of March 27, 1984, at Anchorage, Alaska: U.S. Geological Survey Professional Paper 542-A, p. A3-A68. Rymer, M. J., and Sirns, J. D., 1976, Preliminary survey of modern glaciolacustrine sediments for earthquake-induced deformat ional structures, south-central Alaska: U.S. Geologicnl Survey Open-Pile Report 76-379, 20 p. Sims, J. D., 1973, EwthqufiKe-induced structures in sediments of Van Norman Lake, Snn Fernando, California: Science, v. 182, no. 4108, p. 162-163.
C-s - - Figure 70.-Products of erosion of intertidal bluffs. Slump flat-lying saturated cohesive mud and sand, as lnrgo as appmximatelv 2 m In maximum dimension. & muaoaus and peatbalk, as large es ebout 15 cm in diameter, eroded from con requences.
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 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 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: F ' i a?.-Intertidal bluffs compose
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 ......................
show all

n Alas - Alaska Division of Geological & Geophysical Surveys - State ...

Create successful ePaper yourself

Delete template?

Save as template?