--> ABSTRACT: Abnormal Processes as Major Influences on Deepwater Seafloor Morphology and Deposition, by Frank Peel, Erik Scott, and Neil Evans; #90906(2001)

Datapages, Inc.Print this page

Frank Peel1, Erik Scott1, Neil Evans2

(1) BHP Petroleum Americas, Houston, TX
(2) BHP Petroleum, London, England

ABSTRACT: Abnormal Processes as Major Influences on Deepwater Seafloor Morphology and Deposition

Mapping of the seabed and the near-surface interval on 3D data in deepwater areas reveals evidence of significant seafloor-sculpting processes that fall outside the normal range of sediment gravity flow and ocean current features. These abnormal processes include episodic ocean currents, slope failure related to salt movement, and pockmark eruption.

Some of these processes redistribute sediment across the sea floor; others create major bathymetric features that influence sediment transport by "normal" processes. In many deepwater areas, these abnormal processes are the dominant control on the near-surface sediment architecture, but they are probably under-recognized in the subsurface.

In the deepwater Gulf of Mexico, regional seabed furrow arrays demonstrate that strong, episodic ocean currents redistribute sediment over >100 miles, locally causing deep erosion. Subsurface expression of these erosion surfaces and depositional dumps can resemble canyons and turbidite fans.

Large-scale slide-block trails at the foot of the Sigsbee Scarp show evidence that some slide blocks moved at high speed, some bouncing over the sea floor before settling in to a steady slide. Some giant-scale slide trails identified in the subsurface resemble incised channels.

Seafloor pockmark fields are common features of the West African margin. In some areas, the pockmarks form self-organizing arrays that have some similarity to erosional canyons. In other areas, near-surface faulting controls the pockmark arrays. Pockmark arrays form sediment conduits that could control turbidity current flow. Major pockmark eruption episodes remobilize large volumes of sediment down the slope.

All these processes are poorly understood, and their influence may be under-recognized.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado