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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 67 (1983)

Issue: 3. (March)

First Page: 517

Last Page: 518

Title: The Geomorphic Evolution of the Taylor Black Prairie Between the Trinity and Colorado Rivers: ABSTRACT

Author(s): James A. Montgomery

Article Type: Meeting abstract


The Taylor Black Prairie is an interesting and complex area that has been, heretofore, relatively ignored as a distinct geomorphic unit. Therefore, the purpose of this study is to describe the region as it exists at the present time and to speculate on its overall evolutionary development.

Based on descriptive geomorphic variables including geology, landform morphology, soil type and distribution, surface gravure, vegetation type and distribution, and land use, the Taylor Black Prairie may be subdivided into three north-to-south trending geomorphic areas. These are, from west to east, the Lower Taylor Prairie, the Wolfe City scarp, and the Upper Taylor Prairie. There is also present, in the southern region of the study area, a relatively distinct small exposure of high gravels located between Little River and Brushy Creek. Because these gravels are geographically restricted within the study area, and because they are dissimilar petrologically from the Cretaceous strata upon which the north-to-south prairies are developed, they constitute a distinct geomorphic area.

The dominant active processes in the Taylor Black Prairie are soil erosion and mass wasting. These are acting under present climatic conditions to shape and modify and topography of this region.

The geomorphic evolution of the Taylor Black Prairie is related to the deposition of Tertiary Uvalde Gravel in the central Texas region. These sediments were carried by major rivers from the edge of the southern High Plains eastward through valleys entrenched in Paleozoic and Comanchean rocks. The less-resistant Gulfian and Tertiary rocks allowed valley widening, thus forming braided alluvial streams that deposited humid alluvial fans.

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Topographic development was further enhanced by changes in climate and fluvial response during glacial and interglacial periods. Glacial periods were characterized by increased rainfall which resulted in downcutting and erosion of the divides by major rivers. Interglacial periods were characterized by a rise in regional base level accompanied by fluvial aggradation. The net effect has been a reversal of topography in which the Uvalde Gravel, which occupied the bottom of river valleys at the time of deposition, now caps the highest divides. Studies of modern erosion rates indicate that man's activities, mainly agricultural, have greatly increased the rate of landscape evolution.

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