--> ABSTRACT: Post-Cretaceous Geomorphic Modification of Wichita Paleoplain: a Study in Character and Development of an Unconformity, by Chris Barker; #91038 (2010)

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Post-Cretaceous Geomorphic Modification of Wichita Paleoplain: a Study in Character and Development of an Unconformity

Chris Barker

Cretaceous rocks of northwest Texas were deposited over a landscape of Paleozoic strata, thus forming a major unconformity. That ancient landscape, the Wichita paleoplain, has been exhumed by erosion of the Cretaceous cover, thereby exposing an unconformity surface in various stages of modification.

Streams ancestral to today's drainage began to form as Cretaceous seas retreated. Cretaceous dendritic drainage was gradually lowered onto a series of west-dipping Paleozoic strike ridges. Consequent trunk streams were relatively unaffected by this process, but tributaries were realigned into trellis drainage within subsequent shale valleys. High-gradient streams on the newly re-exposed paleoplain eroded headward into the Cretaceous cover. Relief on the exhumed landscape increased, and accordant summits within the Paleozoic migrated to the west by homoclinal shifting. Neogene deposits temporarily buried parts of the paleoplain and still form its western boundary. Salt dissolution and collapse contributed to beheading of several rivers that drain the Paleozoic outcrop belt. Stream capt res within the paleoplain reorganized western tributaries of the Brazos into prominent right-angle bends. Present drainage is creating several sites of imminent stream capture within and around the perimeter of the Wichita paleoplain.

This problem in regional geomorphology has importance in explaining aspects of subaerial unconformities and their relationship to applied geology, as in the exploration for oil and gas along unconformity surfaces.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.