1984 Results of trans-Alaska crustal transect in Chugach Mountains and Copper River Basin, Alaska
Conference
·
· Am. Assoc. Pet. Geol., Bull.; (United States)
OSTI ID:5854694
The Trans-Alaska Crustal Transect (TACT) program, a multidisciplinary investigation of the continental crust and its evolution along the Trans-Alaska pipeline corridor was started by the USGS during 1984. Preliminary results of geologic, geophysical, and wide-angle reflection/refraction data obtained across the Chugach terrane (CGT) and the composite Wrangellia/Peninsular terrane (WRT/PET) suggest the following: (a) the CGT is composed of accretionary sequences that include, from south to north, Late Cretaceous schistose flysch, uppermost Jurassic to Early Cretaceous sheared melange, and Early(.) Jurassic blueschist/greenschist. (b) The CGT accretionary sequences have local broad, low-amplitude magnetic or gravity anomalies. (c) Seismic data show that the CGT along latitude 61/sup 0/N, by alternating high- (6.9-8.0. km/sec) and low-velocity layers is suggestive of multiple thin slices of subducted oceanic crust and upper mantle. (d) Mafic and ultramafic cumulate rocks along the south margin of the WRT/PET have strong magnetic and gravity signatures and are interpreted as the uplifted root of a Jurassic magmatic arc superimposed on a late Paleozoic volcanic arc. Magnetic data suggest that comparable rocks underlie most of the PET. (e) The Northdipping border Ranges fault (BRF) marks the suture along which the northern margin of the CGT was relatively underthrust at least 40 km beneath the WRT/PET. (f) Beneath the northern CGT and southern WRT/PET, a prominent seismic reflector (v = 7.7 km/sec), suggestive of oceanic upper mantle rocks, dips about 3/sup 0/N and extends from a depth of 12 km beneath the Tasnuna River to 16 km beneath the BRF, where the dip appears to steepen to about 15/sup 0/ beneath the southern margin of the PET.
- Research Organization:
- Geological Survey, Menlo Park, CA
- OSTI ID:
- 5854694
- Report Number(s):
- CONF-8505215-
- Conference Information:
- Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 69:4
- Country of Publication:
- United States
- Language:
- English
Similar Records
Accretion and subduction tectonics in the Chugach Mountains and Copper River Basin, Alaska: initial results of the Trans-Alaska Crustal Transect
Accretion, subduction, and underplating along the southern Alaska continental margin
Geochemistry of siliciclastic rocks in the Peninsular, Chugach, and Prince William terranes: Implications for the tectonic evolution of south central Alaska
Journal Article
·
Sun Jun 01 00:00:00 EDT 1986
· Geology; (United States)
·
OSTI ID:5549495
Accretion, subduction, and underplating along the southern Alaska continental margin
Conference
·
Mon Dec 31 23:00:00 EST 1984
· Geol. Soc. Am., Abstr. Programs; (United States)
·
OSTI ID:6319653
Geochemistry of siliciclastic rocks in the Peninsular, Chugach, and Prince William terranes: Implications for the tectonic evolution of south central Alaska
Conference
·
Tue Dec 31 23:00:00 EST 1991
· Geological Society of America, Abstracts with Programs; (United States)
·
OSTI ID:5588306