Abstract: Oceanic Bolide Impacts: Deformation Characteristics and Petroleum Potential

Wylie C. Poag, David S. Powars, Scott Bruce

Two Eocene bolide impact structures, one on the New Jersey Outer Continental Shelf, the other beneath Chesapeake Bay, display reservoir, sealing, and trapping characteristics essential to hydrocarbon systems. The potential reservoirs consist of 200-to 2,000(?)-m-thick, instantaneously deposited breccias, mainly of autochthonous sedimentary intraclasts, which fill the deep central depressions and spread laterally around them for 10-40 km. In three dimension, the breccia bed resembles an inverted sombrero, whose broad brim fills a relatively flat-floored, subcircular excavation, encircling a central depression. The breccia is seismically expressed as a zone of chaotic or disrupted reflections. The breccia is believed to have been created by fracturing during the initial hypervelocity im act, by hydraulic sea-floor excavation and redeposition during post-impact collapse of a 500-to 1,000-m water column, and by subsequent turbulence from a super tsunami.

The relatively high porosity and broad distribution of the breccia, which, in the case of the Chesapeake Bay structure, covers approximately 6,400 sq km, make it a potentially superb hydrocarbon reservoir. The breccia at both sites is capped by a relatively thin (60-100 m) bathyal clay, which seals the reservoir. Subsequent burial and compaction faulting have created numerous structural traps within the breccia. Under appropriate source-rock and geothermal regimes, analogous bolide structures could provide significant targets for hydrocarbon exploration.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994