Stratigraphy of Glen Rose Formation, Gulf coastal plain

Strata of the Glen Rose Formation and equivalent units crop out in a continuous band across the Edwards Plateau, the area of outcrop skirting the Llano uplift, the Lampasas cut plain, north-central Texas, southeastern Oklahoma, and southwestern Arkansas. These rocks dip into the subsurface of the Gulf coastal plain. Although the Glen Rose interval has been studied on outcrop and in the subsurface in these areas through numerous investigations of local scale and several regional review papers, a synthesis integrating subsurface with outcrop across the broad region and a more detailed lithostratigraphic framework are needed. On outcrop on the Edwards Plateau, the Glen Rose is divided into upper and lower members by the Corbula bed, a thin but widespread accumulation of the minute clam Carycorbula matinae. In this region, the Corbula bed lies beneath anhydrite and gypsum beds (dissolution zones on outcrop), which may be traced through laterally equivalent limestones in the subsurface around the Llano uplift to thin anhydrite stringers above the Ferry Lake Anhydrite in northeastern Texas. These stringers may be traced to the lower part of the Thorp Springs Member of the Glen Rose din the subsurface and outcrop area of north-central Texas. In the Paluxy Rivermore » Valley, the Corbula bed occurs beneath the Thorp Springs. This specific correlation allows clear demarcation between beds of the upper and lower Glen Rose members in the region. Correlation of this type within the Glen Rose interval allows a detailed understanding of the depositional history of this sequence and provides a more explicitly defined lithostratigraphic framework into which future studies may be integrated.« less