Evaporite deformation in the Sierra Madre Oriental, northeastern Mexico: Décollement kinematics in an evaporite-detached thin-skinned fold belt

Gareth Cross

The University of Texas at Austin, Department of Geological Sciences

Austin, TX 78705

[email protected]

Evaporite-detached folds and thrusts are a common tectonic element in thin-skinned orogenic belts and in gravity-driven contractional systems. Structures preserved within evaporite décollements have important implications for fold-thrust kinematics in such settings. However, the kinematics of structural development within evaporite décollements has been little studied. This project will examine the structures preserved within the décollement of the Laramide-aged Sierra Madre Oriental fold-thrust belt of northeastern Mexico, in order to deduce the kinematic evolution of detachment folds in the overburden. The deformation style in the central Sierra Madre Oriental is characterized by kilometer-scale detachment folds developed above Upper Jurassic evaporites. Décollement exposures, uplifted by a late-stage basement-involved anticline, preserve a diverse suite of well-exposed structures. Therefore, I will carry out fieldwork that will comprise lithologic and structural mapping, together with strain measurement of mesoscopic kinematic indicators. Fundamental to the fieldwork will be comparison between mesoscopic structures developed in different structural domains in the décollement (relative to macroscopic folds in the overburden), and the variation in strain magnitude and structural style with stratigraphic position. Microstructural analysis of representative samples will furnish further information on the strain and kinematics represented by each structure type, and the cross-cutting relationships between structures. The anticipated product of the investigation is a geometric description of the suite of structures developed in the décollement, together with a kinematic model that describes the development of these structures. This model will improve understanding of the tectonic development of evaporite-detached orogenic belts, and will be applicable to other such belts worldwide.

AAPG Search and Discovery Article #90060©2006 AAPG Foundation Grants-in-Aid