| Abstract | The San Marcos Arch is a subsurface feature of Central Texas that is thought to have been an active high during portions of the Cretaceous, affecting the depositional patterns of the sediments deposited during that period. While typically referred to as the San Marcos Arch, some articles refer to the same structure as the San Marcos Platform, indicating a structure with no apex. Understanding the structure of the San Marcos Arch/Platform and identifying its location in the subsurface is significant for exploration geologists operating in Central Texas. Among the affected strata is the Eagle Ford Group, a mudrock known for its abundant hydrocarbon content that is a major unconventional reservoir. Thinning of the Eagle Ford over the top of the San Marcos Arch has been observed for many years and directly affects hydrocarbon exploration in the area. To better understand the nature of the structural feature, formation tops were used to build isopach and structure maps for Cretaceous strata including the Eagle Ford Shale, the Buda Limestone, and the Del Rio Shale; these tops were picked on raster well logs. From these methods it is interpreted that "San Marcos Platform" may be a more accurate name for the Central Texas structure. |
