--> ABSTRACT: Mechanical Stability of Carbonate Platform Margins, by Juan Contreras and Max Suter; #90906(2001)

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Juan Contreras1, Max Suter2

(1) CICESE, Ensenada, BC, Mexico
(2) Universidad Nacional Autonoma de Mexico, Hermosillo, Son, Mexico

ABSTRACT: Mechanical Stability of Carbonate Platform Margins

It has been documented in several fold-and-thrust belts that carbonated banks deform in a dual manner to compressive deviatoric stress. A clear example of this is the Valles-San Luis Potosi carbonate bank in east-central Mexico in which the deformation is concentrated along the platform margin in the form of thrust faults, while the interior of the bank deforms by parallel folding. To understand why the margins of carbonate platforms become unstable, we carried out a finite element modeling of the deformation of these geological structures. We used a simple linear elastic rheology and prescribed displacements as boundary conditions. We calculated the unstable areas and potential fracture planes using the Mohr-Coulomb fracturing criterion. With this finite element model we also explore if the high primary porosity in the foreslope region could also have played a role in this phenomenon, i.e., the high pore pressure could have helped to the development of fractures at the edge of the platform. Our modeling predicts that the platform margin remains stable when no pore pressure is considered. By contrast, the margin becomes unstable when pore pressure is considered. Also the modeling predicts the formation of an intra-bank detachment with a ramp-flat-ramp geometry. This detachment is a boundary effect controlled by the complicated geometry of these structures. This last prediction is in agreement with geological observations at the Valles-San Luis Potosi carbonate platform.

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