Sedimentology and Kinematic Restoration of Growth-Faulted Sand Bodies in the Cretaceous Ferron Notom Delta, Utah

Jarratt Kelso
University of Houston, Department of Earth and Atmospheric Sciences Houston, Texas

Superb cliff-side exposures of growth-faulted sand bodies in the fluvio-deltaic Cretaceous Ferron Sandstone provide excellent outcrop analogs for subsurface reservoir compartments created by growth faulting. The field area is approximately fifteen miles by road northwest of the town of Hanksville, Utah, in the area of Coal Mine Wash, and this study is part of an ongoing regional sequence stratigraphic interpretation of the informally named Ferron Notom Delta. The purpose of this study is to investigate the relationship between sedimentary facies and growth faulting, and to elucidate the style and degree of deformation of underlying pre-growth prodelta mudstones and siltstones. The cliff-side exposures are approximately fifty meters high and require the use of ropes to record detailed measured sections. Eight detailed measured sections through the pre-growth, growth, and post-growth strata reveal a highly river-dominated deltaic setting during the deposition of these rocks. A low abundance and diversity of ichnofossils, inverse to normal grading of prodelta mudstones and siltstones, and mantle and swirl structures indicate hyperpycnal conditions at the time of deposition. Accommodation for the five meter thick wedges of growth-faulted sandstones is restricted to the uppermost few meters of the prodelta siltstones; with non-penetrating diapir structures composed of brittly deformed siltstones located between adjacent growth-faulted sand bodies. Photomosaics of the outcrop allow structural restoration of the beds to pre-growth conditions and provide a link between sedimentation and growth faulting.

AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid