SEISMIC-REFRACTION MEASUREMENTS WITHIN THE PENINSULAR TERRANE, SOUTH CENTRAL ALASKA

被引:3
作者
AMBOS, EL [1 ]
MOONEY, WD [1 ]
FUIS, GS [1 ]
机构
[1] US GEOL SURVEY, MENLO PK, CA 94025 USA
基金
英国经济与社会研究理事会; 英国工程与自然科学研究理事会;
关键词
D O I
10.1029/94JB02621
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
We present an interpretation of crustal seismic refraction data from the Peninsular terrane, one of the many exotic terranes that have been accreted to the continental margin of southern Alaska in the past 200 m.y. A seismic refraction line was collected along the Glenn Highway in the Copper River Basin of south central Alaska in 1984 and 1985, as part of the U.S. Geological Survey Trans-Alaska Crustal Transect (TACT) program. P wave velocities of 2.7-3.5 km/s and thicknesses of 1-2 km characterize post-lower Jurassic sedimentary rocks that underlie most of the seismic refraction line. An average crustal velocity structure includes the following five velocity divisions. Beneath the sedimentary rocks lie 1-2 km of 4.0-4.6 km/s materials, correlating with andesitic volcaniclastic sedimentary rocks and lava flows of the Lower Jurassic Talkeetna Formation. Below these rocks, seismic velocity increases rapidly, from 5.0 to 6.1 km/s, in 2-3 km. At 7-8 km depth, velocity jumps to 6.3 km/s and increments to 6.6 km/s by 10-12 km depth. Velocities increase from 6.8 to 7.0 km/s between 12 to 20 km depth. At about 22 km depth, a jump in velocity from 7.0 to 7.4 km/s is inferred but is poorly resolved. Depth to the Moho discontinuity could not be determined from our data. The absence of clear PmP reflections may indicate that Moho is deeper than 40 km. Data from two offset shotpoints northeast of the line and within the Wrangellia terrane constrain the deep structure transition between Peninsular and Wrangellia terranes. The 6.3-6.6 km/s material thickens to the northeast, toward the suture between Peninsular and Wrangellia terranes, but southwest of its mapped trace at the West Fork fault. Peninsular terrane crustal structure appears dissimilar to that of continental interiors. It is similar to velocity structures determined for accreted island are fragments in California, such as the basement of the Great Valley and the Klamath Mountains.
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收藏
页码:4079 / 4095
页数:17
相关论文
共 87 条
[1]  
ANDREASON EG, 1964, US GEOL SURV PROF PA, V316, P135
[2]  
BEAUDOIN BC, 1992, J GEOPHYS RES-SOL EA, V97, P1921, DOI 10.1029/91JB02881
[3]   CRUSTAL STRUCTURE IN ALASKA [J].
BERG, E .
TECTONOPHYSICS, 1973, 20 (1-4) :165-182
[4]   THE VELOCITY OF COMPRESSIONAL WAVES IN ROCKS TO 10-KILOBARS .1. [J].
BIRCH, F .
JOURNAL OF GEOPHYSICAL RESEARCH, 1960, 65 (04) :1083-1102
[5]  
BLANK HR, 1979, 259 US GEOL SURV SAU
[6]  
BLUNDELL DJ, 1984, WORKSHOP P INTERPRET, P177
[7]   OVERPRINT MAGNETIZATIONS IN SUPPORT OF NORTHWARD DISPLACEMENT OF THE CHUGACH-PRINCE-WILLIAM-TERRANE, ALASKA [J].
BOL, AJ .
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH, 1993, 98 (B12) :22389-22400
[8]   GUIDE TO INTERPRETATION OF CRUSTAL REFRACTION PROFILES [J].
BRAILE, LW ;
SMITH, RB .
GEOPHYSICAL JOURNAL OF THE ROYAL ASTRONOMICAL SOCIETY, 1975, 40 (02) :145-176
[9]   THE BORDER RANGES ULTRAMAFIC AND MAFIC COMPLEX, SOUTH-CENTRAL ALASKA - CUMULATE FRACTIONATES OF ISLAND-ARC VOLCANICS [J].
BURNS, LE .
CANADIAN JOURNAL OF EARTH SCIENCES, 1985, 22 (07) :1020-1038
[10]  
BURNS LE, 1982, 82460 US GEOL SURV O