Deep-crustal structure of the continental margin adjacent to the eastern Aleutian trench

Conference · Fri Jun 01 04:00:00 EDT 1990 · AAPG Bulletin (American Association of Petroleum Geologists); (USA)

OSTI ID:6317179

Fisher, M A; Brocher, T M; Bruns, T R; Geist, E L ^[1]

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1. Geological Survey, Menlo Park, CA (USA)

Onshore and marine seismic-reflection data obtained near the Trans-Alaskan Crustal Transect (TACT), in the region of the eastern Aleutian trench and lower Cook Inlet, reveal highly reflective midcrustal layering that begins at a depth of 10-15 km within the upper plate of the Aleutian subduction zone. Beneath the continental shelf, midcrustal reflections were recorded over broad areas and occur in subhorizontal bands that are 1 to 3 s thick. The reflections extend beneath complexly deformed late Mesozoic and early Cenozoic accreted rocks that are exposed at the surface. Preliminary interpretation of seismic refraction data indicates that under the shelf the top of the reflections corresponds in depth with a sharp increase in rock velocity, from 5.9 km/s to 6.6 km/s. North and northwest of the shelf, beneath the Chugach and Kenai mountains, midcrustal features dip 20{degree}-30{degree} north or northwest, and below the Chugach Mountains, the top of the reflections corresponds to a velocity decrease from 6.5 to 5.7 km/s. The cause of the midcrustal reflections may vary geographically and could include underplated Eocene deep-sea fan deposits, the top of the subducted Yakutat terrane, a midcrustal decollement, or a transition from brittle to ductile deformation regimes.

• OSTI ID: 6317179
• Report Number(s): CONF-900702--
• Conference Information: Journal Name: AAPG Bulletin (American Association of Petroleum Geologists); (USA) Journal Volume: 74:6
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALASKA
ALEUTIAN ISLANDS
ALLUVIAL DEPOSITS
CENOZOIC ERA
CONTINENTAL MARGIN
FEDERAL REGION X
GEOLOGIC AGES
GEOLOGIC DEPOSITS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
ISLANDS
NORTH AMERICA
OFFSHORE SITES
PACIFIC OCEAN
SEAS
SEISMIC SURVEYS
SURFACE WATERS
SURVEYS
TERTIARY PERIOD
USA