Reconstructing the Paleo-Hydraulics of Channelized Turbidity Currents From the Submarine Channel Deposits of the Brushy Canyon Formation, West Texas

Abstract

Interpretations of submarine channel deposits are often over-shadowed by a few basic questions: Were turbidity currents contained within the channel? What were their concentrations? What were their velocities? How thick were they? These parameters are necessary inputs in many computational models. We will present estimates of the hydraulic characteristics of paleo-flows responsible for sediment sorting within the Brushy Canyon Formation channel deposits, on the upper-slope and basin floor of the Paleozoic Delaware Basin. The depositional facies on the upper slope fall into two broad classes: A) open-channel facies associated with bypass of sediment to deeper water; and B) channel-filling facies associated with bed aggradation and significant loss of channel relief. Deposits accumulating during bypass are interpreted to be eddy bars located in bank-attached zones of flow separation. These deposits are characterized by packages of steeply inclined beds composed of planar-stratified, trough cross-stratified or sub- to super-critically climbing rippled deposits (D50=110μm). The channel-filling deposits form thick-bedded, sometimes gravel-rich, sandstone bodies which are structureless or which display stratification associated with migrating dunes and intra-channel barforms (D50=156μm). On the proximal basin floor, the channel-filling sandstones (D50=110μm) are dominated by stratification associated with trains of dunes climbing at sub- to super-critical angles, indicating high rates of deposition from suspension. We use modified sediment transport relationships, originally developed for fluvial environments, to characterize the bulk properties of paleo-flows that constructed turbidite strata in the Brushy Canyon channels. Bed geometries, sedimentary structures and grain-size data, used with these relationships, show that the studied channel strata were constructed from turbidity currents that were dilute (concentrations less than 5%), had depth-averaged velocities between 0.96–1.56m/s and were at least 15m thick.

AAPG Datapages/Search and Discovery Article #90216 ©2015 AAPG Annual Convention and Exhibition, Denver, CO., May 31 - June 3, 2015