D. C. Twichell¹, A. K. Cooper²
(1) U. S. Geological Survey, Woods Hole, MA
(2) U. S. Geological Survey, Menlo Park, CA

Abstract: Relation between seafloor failures and gas hydrates in the Gulf of Mexico: A regional comparison

An association of slope failures with gas hydrates has been observed on some continental slopes. However, in the Gulf of Mexico, this potential relationship is masked by a complex seafloor morphology, deformation of the shallow stratigraphy by salt, and an incomplete understanding of hydrate distribution. To define this relationship better, multibeam bathymetry and GLORIA sidescan sonar imagery have been integrated to map the regional distributions of gas hydrates and slope failures that are exposed on the seafloor. Gas hydrates have been observed on the seafloor mostly on the tops of salt structures, and these locations consistently coincide with distinctive high-backscatter patches on the sidescan imagery. The regional mapping suggests many more seafloor exposures of hydrates, and most occurrences coincide with the crests and flanks of salt structures. The headwall scarps of most failures originate on the flanks of bathymetric highs where gradients exceed 10 degrees, and the deposits derived from the failures partially or completely cover the adjacent basin floors. A detailed study of one basin, downslope of a potential hydrate area, showed the floor to be covered by several overlapping deposits showing that slope failure was a multi-staged process rather than a single event. The regional comparison shows that slope failures commonly, although not always, occur downslope of hydrate exposures. The widespread spatial proximity of many of the slope failures and seafloor hydrate deposits suggests that the two are linked, and that these features result from subsurface processes that are only partly revealed in the surficial geology.

AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana