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Slope and Basinal Deposits Shed from a Late Wolfcampian Tectonically-Active Carbonate Ramp Margin

By

PLAYTON, TED E.

Bureau of Economic Geology, John A. and Katherine G. Jackson School of Geosciences, The University of Texas at Austin, Austin, TX

 

Outcrops in the Victorio Flexure area, Sierra Diablo, west Texas, demonstrate that Ouachita-related tectonism was active into the Permian and that channelized, deep-water carbonate processes occur at the channel-complex scale. The Victorio Flexure is a major fault-zone that was active in the western Permian Basin during late Paleozoic deformation. In early Permian (Wolfcampian) time, uplifted strata along the Victorio Flexure was eroded and sourced terrestrial clastic alluvial and fluvial systems. A marine transgression flooded the landscape and initiated carbonate production as clastic influx waned. Outer shelf wackestones and packstones were initially laid down, followed by the deposition of platform packstones as sea level stabilized. Platform progradational extent was controlled by subtle topography associated with the Victorio Flexure, and a structurally-modified ramp existed.

In latest Wolfcampian time, significant movement along the Victorio Flexure increased slope height and gradient, and large volumes of platform- and upper slope-derived material were mobilized downslope. This allochthonous debris formed a slope-centered apron consisting of coalesced, amalgamated and non-amalgamated components. Amalgamated components are primarily mud-rich breccias and are interpreted to be stacked debris flows. Non-amalgamated components consist of allochem-rich to allochem-poor wackestones and packstones, and are interpreted to be lower-density sediment gravity flow packages or periplatform, hemipelagic drapes. Debris flow stacks display a hierarchy of compensational architectural elements where complex-scale packages are composed of bed- or bedset-scale units. The stacking geometries of these complexes imply focused flow conditions (channelization) and updip point sources. This slope apron defines the top of a third-order Wolfcampian sequence.