ABSTRACT: Physical Aspects of Salt-Sediment Interaction and the Evolution of Minibasins

Heaney, Richard J.¹ 
(1) ConocoPhillips, Houston, TX

ABSTRACT: Physical Aspects of Salt-Sediment Interaction and the Evolution of Minibasins

It has long been recognized that passive downbuilding of minibasins into the salt is responsible for the bulk of salt-sediment interaction. However, the actual process of passive downbuilding has not been studied in a systematic way, starting from physical principles and rock properties. A simple mathematical analogue for salt-sediment interaction has been used to investigate the development of minibasins in the Gulf of Mexico. The equations governing the interaction allow calculation of the topographic relief of the minibasin/salt wall system at various stages in minibasin evolution, which is an important factor controlling turbidite deposition. Determination of parameters used in the mathematical modeling, reveals the unexpected result that overall minibasin density can be less than salt density, even when the minibasin is 12,000 feet thick. The equations also indicate that, if the top of the minibasin is not covered by salt, it will continue to float on top of the salt, in some cases until it grounds out. Thus, we would expect that most Gulf of Mexico minibasins of shallow to moderate depth, and even some of the very thick ones, are floating on the underlying salt. The floating minibasin concept allows us to better predict how the overall salt-sediment system evolves. A consequence of the floating minibasin concept is that minibasins can be carried along in the net flow of salt towards the toe of the overall salt-sediment system. Interactions between these “migrating” minibasins and grounded minibasins can lead to unexpected age relationships between suprasalt and subsalt minibasins.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.