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Title: Impact origin of the Avak structure, Arctic Alaska, and genesis of the Barrow gas fields

Conference · · AAPG Bulletin (American Association of Petroleum Geologists); (USA)
OSTI ID:6983867
;  [1]
  1. Geological Survey, Menlo Park, CA (USA)

Geophysical and subsurface geologic data confirm that the Avak structure, which underlies the coastal plain 12 km southeast of Barrow, is an impact crater. The structure is a roughly circular area of chaotically deformed Upper Triassic to Lower Cretaceous sedimentary rocks 8 km in diameter bounded by a ring of anastomozing, inwardly dipping, listric normal faults. Beyond the ring, these rocks are almost flat. Basement is strongly deformed Ordovician and Silurian argillite. Strong density and seismic velocity contrast between the argillite and the overlying strata produce gravity and seismic reflection signatures that define ring anticlines around the disturbed zone and a structural high at its center. The Mesozoic strata are about 760 m thick in the adjacent Barrow gas fields, where the Neocomian pebble shale unit and the gas-producing Lower Jurassic Barrow sandstone lie at average subsea depths of 438 m and 670 m, respectively. In the Avak well, drilled on the central high, the pebble shale unit and Barrow sandstone lie near the surface, documenting more than 500 m of uplift at the high. The cores in this well also show steep dips (30-90{degree}), abundant tectonic breccia with argillite clasts 90 m above basement, fractured quartz grains, and shatter cones resembling those found in well-documented meteorite craters. Stratigraphic data suggest that the Avak meteorite struck a late Early Cretaceous marine shelf, produced peripheral highs that trapped gas in the Barrow fields, and triggered massive landslides on the adjacent outer shelf. The age of the landslides dates the impact at about 105 Ma.

OSTI ID:
6983867
Report Number(s):
CONF-900605-; CODEN: AABUD
Journal Information:
AAPG Bulletin (American Association of Petroleum Geologists); (USA), Vol. 74:5; Conference: Annual convention and exposition of the American Association of Petroleum Geologists, San Francisco, CA (USA), 3-6 Jun 1990; ISSN 0149-1423
Country of Publication:
United States
Language:
English