Growth Faults at the Prodelta to Delta-Front Transition, Cretaceous Ferron Sandstone, Utah
J. P. Bhattacharya1 and R. K. Davies2
1University of Texas at Dallas, Richardson, TX
2Rock Deformation Research, USA Inc, McKinney, TX
Cliff exposures of synsedimentary growth faults at the base of the Cretaceous Ferron sandstone in central Utah represent outcrop analogs to subsurface growth faulted reservoirs. Delta front sands prograded over and deformed less dense prodelta muds of the underlying Tununk Shale. Growth faulting is initiated by deposition of crossbedded distributary channel and mouth bar sandstones that reach 9m thick in the hanging walls of the faults. Cross-bed sets decrease from meter to decimeter scale suggesting decreasing flow velocity away from the faults.
The most proximal and most distal fault sets were the earliest active faults. Curvature of the beds in the hanging walls of the faults nucleates smaller conjugate fault sets. Detailed fault patterns and associated facies changes demonstrate a complex fault history and style for growth fault development rather than a simple progressive development of faults from nearshore to farshore. This likely results from complex shifts in depositional loci, including upstream and downstream accretion of mouth bar sands.
AAPG Search and Discovery Article #90905©2001 AAPG Southwest Section Meeting, Dallas, Texas