Effect of carbonate platform morphology on syndepositional deformation: Insights from numerical modeling

Abstract

We use finite element numerical modeling to show that carbonate platform morphology is a control on syndepositional deformation in steep-walled carbonate platforms. We simulate gravity application on three end-member carbonate platform margin morphologies: (1) a mixed planar-concave up shaped shelf margin from Tobacco Cay, Belize, (2) a concave up shaped system representing the Capitan Profile, Guadalupe Mountains West Texas, and (3) a sigmoidal, Jurassic Amellago ramp. We model the platform material with a brittle failure criteria that captures tensile and shear failure. We show that the presence of a vertical reef wall and, thereby, lack of lateral confining stress seaward leads to a tensile stress state in the middle of the shelf and the shelf edge, promoting the development of opening-mode (Mode I) tensile fractures. Fractures occur in the absence of additional loading or burial, indicating that their formation is consistent with a syndepositional setting. Overall, our results demonstrate that carbonate platforms with a near vertical reef wall are routinely modified by syndepositional deformation and failure in the absence of compaction. We show that zones of high tensile stress can result in brittle, tensile failure and confirm that tensile failure is a critical element of building and may contribute to maintaining steep-walled carbonate platform systems.