ABSTRACT: Mitra and Karam

Authors:
Shankar Mitra and Pierre Karam
ConocoPhillips School of Geology and Geophysics, University of Oklahoma, Sarkeys Energy Center, Ste. 710, 100 E. Boyd St., Norman, Oklahoma 73019

Controls of the Geometry and Evolution of Salt Diapirs: Louann Salt, East Texas

Session:
Salt Tectonics—Gulf of Mexico and the World (GRBCC, Room 310ABC)
Monday, September 21, 2015, 9:00 am

Abstract:
Experimental models show that the shapes and evolution of the salt diapirs are controlled by the rate of sedimentation, the sediments load and density, and the original thickness of the salt layer. An adequate balance between these factors initiates movement, and also dictates the growth mechanism and the shapes of diapirs. With sufficient sediment load and below a critical sedimentation rate, the diapirs taper when the rate of sedimentation (Vs) exceeds the rate of salt movement (Vr), and flares when Vs in less than Vr. Furthermore, the rate of sedimentation directly controls the rate of salt movement, except when the salt supply is reduced due to the thickness of the salt layer. The evolution of complex diapirs in salt basins can be better understood using these principles. The Louann Salt in the East Texas Basin evolved into fully or partially developed salt structures. Variations in diapir geometry and shape can be directly related to changes in the rates of sedimentation in the basin. The sedimentation rate decreased from the Lower to the Upper Cretaceous and Paleocene, and then increased again during the Eocene. These changes led to a number cylindrical and flared diapirs formed primarily by a passive mechanism followed by a rapid tapering and occlusion during the Eocene. Earlier occlusion and tapering in some diapirs can be explained as due to a reduced salt supply, resulting in a decrease in the rate of salt flow.