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ABSTRACT: Regional Basinal Sandstone depositional Patterns During the Guadalupian (Late Permian), Delaware Basin, West Texas--New Mexico

Jonathan H. Geisen, Peter A. Scholle

Examination of well logs from more than 300 Delaware basin wells penetrating the Bell Canyon and Brushy Canyon formations has allowed definition of regional depositional patterns during the Late Permian

(Guadalupian). Characteristic gamma-ray hot-kicks mark thin but widespread calcareous shales or limestones representing starved basin sedimentation during sea level highstands. Correlation of such markers along three strike and ten dip lines permitted isopaching of intervening lowstand clastic wedges.

The low-stand wedges typically thin significantly from basin margin to basin center and are marked by a prominent linearity oriented perpendicular to the margin. These lineations probably represent channelized turbidite and grain-flow deposits. Most intervals show dozens of such lineations indicating multiple input points for terrigenous detritus rather than just a few major point sources of debris. The resulting deposits appear to be more apron-like than fan-like and coalesce into broad, sheet-like deposits toward the basin center. Isopach thicks vary in position through time, but terrigenous sediment transport is predominantly from northerly directions throughout the analyzed interval. Thus, the filling of the Midland basin at the close of Cherry Canyon deposition did not result in major new source of terrigenous debris from the east (Central Basin platform).

The well-sorted nature of the basinal sands, their widely distributed input points, apron-like geometry, and other factors argue for migration of eolian dunes to the shelf margin during sea level lowstands. Transport of these well-sorted, unconsolidated sands into the basin was not, however, mainly by direct eolian processes as has been proposed recently, but must have involved submarine current mechanisms.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990