Abstract

Sedimentologic data and regional correlation based on seismic and field data constrain depositional models for basinally restricted siliciclastics of the Brushy Canyon Formation and sandstones of the immediately overlying Cherry Canyon Tongue. In the Guadalupe Mountains, the Brushy Canyon thins at the basin margin, from 300m to pinchout, by onlap onto a basinward sloping submarine unconformity. The onlapping wedge contains numerous basinward-trending channels (up to 50m deep and 1 km wide). Laminated siltstones comprise interchannel areas and occur in channels as draping units of constant thickness. Sandstones (rippled, parallel laminated, and massive beds) are restricted to channels and onlap channel walls. Concentration of sandstones in vertically stacked, 20-50m deep channels suggests sands were point-sourced into the basin. Increasing proportions of high energy deposits in successive sandstone channel fills indicate progradation of the Brushy Canyon wedge. Correlation of the Brushy Canyon unconformity shelfward to an interpreted disconformity within the San Andres Formation suggests that the shelf was subaerially exposed. Allochthonous fossils in the Brushy Canyon indicate existing submerged, shallow, upper slope areas were normal marine. The internal geometries and facies of the Brushy Canyon, and regional constraints suggest that the density-driven currents which deposited these siliciclastic rocks were turbidity currents rather than saline density currents sourced by hypersaline shelf waters.