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4-D Evolution of Deepwater Fold and Thrust Belts: Dynamic Interactions with Syntectonic Sedimentation and Erosion

Jonny E. Wu and Ken R. McClay
Fault Dynamics Research Group, Royal Holloway, University of London, Egham, United Kingdom

Fold and thrust belts developing in the deepwater environment are generally subject to less erosion and more deposition relative to other environments (i.e. subaerial or shallow marine). Furthermore, the styles of syn-kinematic deposition and erosion are unique as they encompass hyperpycnal flow, hemipelagic deposition and mass transport processes.

Previous (sandbox) analogue model studies of fold and thrust systems show that they respond dramatically to changes in syn-kinematic erosion and deposition. Therefore, the evolution of deepwater fold and thrust belts may be influenced by the unique erosional and depositional conditions that operate in the deepwater environment.

In this study, we compare the effects of differing styles of deepwater syn-kinematic sedimentation on two-dimensional doubly-vergent thrust wedges constructed from thin horizontal sand packs. Syn-kinematic sedimentation was added in a variety of styles including underfilling, deposition to a graded “healed-slope” profile, and slope bypass with deposition on the basin floor.

All models produced a 2D doubly-vergent critically Previous HittaperedTop Coulomb wedge system with a prowedge characterised by low taper wedges with dominant pro-vergent thrust faults and associated backthrusts. Dramatic changes were induced in the pro-wedge geometries - notably with an increase in the spacing of pro-vergent thrusts, a decrease in the number of thrusts, irregular thrust spacing, thrust re-activation, a decrease in backthrusting and adjustments to the angle of thrust faults. Sequential fill in piggyback basins produced variable stratigraphies and different basin infills similar to natural deepwater fold and thrust systems.

 

AAPG Search and Discover Article #90078©2008 AAPG Annual Convention, San Antonio, Texas