Analogue Models of Contractional Thrust Wedges—The Dynamic Effects of Syntectonic Sedimentation and Syntectonic Erosion

Abstract

Critically tapered Coulomb thrust wedges are characteristically formed in deepwater fold and thrust belts such as in delta systems on passive margins such as the Niger delta as well as in contractional terranes such as offshore NW Borneo. These fold and thrust belts display dynamic interactions with both syntectonic sedimentation as well as syntectonic erosion. Scaled analogue sandbox models have proved to be a powerful tool to simulate and analyse the progressive evolution, geometries and kinematics of these fold and thrust belts. In particular the use of digital image correlation techniques (DIC) has permitted the quantitative determinations of strains, displacements and rotations within 2D analogue models of thrust wedges. High-resolution digital photography and animations permit the determination of thrust sequences, thrust fault activities and the progressive evolution of thrust-related folds in these analogue models. The models show that critically-tapered thrust wedges rapidly form from the early stages of contraction achieving a dynamic stable taper angle controlled by the rheology of the basal detachment. Thrusts nucleate in sequence towards the front of the wedge and DIC analyses show simultaneous displacements on several of thrusts throughout the deformation history. Syntectonic erosion and sedimentation change the wedge taper which then responded by internally re-adjusting the thrust geometries and activities to return to a dynamic equilibrium state. The results of these detailed models are compared to 2D seismic sections across deepwater fold and thrust belts in the Niger delta as well as for the contractional fold and thrust belt offshore Sabah.

AAPG Datapages/Search and Discovery Article #90217 © 2015 International Conference & Exhibition, Melbourne, Australia, September 13-16, 2015