ABSTRACT This field trip examines exposures of transgressive and highstand marine deposits of the Sabinetown transgression that forms the upper part of the Calvert Bluff Formation of the Wilcox Group in the outcrop belt. The horizon of maximum flood in the Sabinetown transgression at Bastrop contains molluscs and diverse vertebrate fossils characteristic of open marine environments. The highstand deposits coarsen upward and are capped with a well-developed paleosol. These deposits are dated as early Eocene.

Abstract: An integrated palynological and sedimentological study of Wilcox/Carrizo outcrops in and near Tahitian Village, Bastrop County, Texas, has led to a reevaluation of their chronostratigraphic significance and depositional environments. Strata at the well-known Pine Forest Golf Course and nearby Red Bluff outcrops, together with lesser-known outcrops in the vicinity, are important for source-to-sink linkages with coeval downdip Wilcox Group strata in the deep-water Gulf of Mexico (GOM). This updip succession is fragmentary, with erosional breaks between lithologic units. It represents nearshore shallow-marine to coastal environments throughout, with widespread evidence of tidal influence. Shallow-marine trace fossils are present, and although these are generally sporadic in sandstones, the Calvert Bluff Formation includes extensive Ophiomorpha galleries. Sabinetown Formation parasequences are mostly mud-dominated tidalites with locally common marine trace fossils in more arenaceous intervals. A bioturbated siltstone immediately above the Sabinetown Formation yielded the first Texas record of common to abundant Apectodinium, an acme potentially indicating the Paleocene–Eocene Thermal Maximum (PETM), and thereby providing a correlation with PETM intervals in GOM wells. At all locations, the base of the Carrizo Formation is a marine Glossifungites surface. Siltstone rip-up clasts draped on sigmoidal cross-beds and robust Ophiomorpha indicate the Carrizo Formation probably represents a tidal delta, not fluvial channels.

Abstract Coal deposits in the Wilcox Group of central Texas have been regarded as the richest coal resources in the Gulf Coastal Plain. Although minable coal beds appear to be less numerous and generally higher in sulfur content (1 percent average, as-received basis; table 1 ) than Wilcox coal deposits in the Northeast Texas and Louisiana Sabine assessment areas (0.5 and 0.6 percent sulfur, respectively; table 1 ), net coal thickness in coal zones in central Texas is up to 32 ft thick and more persistent along strike (up to 15 mi) at or near the surface than coals of any other Gulf Coast assessment area. The rank of the coal beds in central Texas is generally lignite (table 1 ), but some coal ranks as great as subbituminousC have been reported (Mukhopadhyay, 1989). The outcrop of the Wilcox Group in central Texas strikesnortheast, extends for approximately 140 mi between the Trinity and Colorado Rivers, and covers parts of Bastrop, Falls, Freestone, Lee, Leon, Limestone, Milam, Navarro, Robertson, andWilliamson Counties (Figure 1 ). Three formations, in ascending order, the Hooper, Simsboro, and Calvert Bluff, are recognized in central Texas (Figure 2 ). The Wilcox Group is underlain conformably by the Midway Group, a mudstone-dominated marine sequence, and is overlain and scoured locally by the Carrizo Sand, a fluvial unit at the base of the Claiborne Group.

ABSTRACT This trip follows part of the route taken by E.T. Dumble, R.A.F. Penrose, Jr. (later president of and great benefactor to the Geological Society of America), and R.T. Hill as they surveyed the geology from the vantage point of the Colorado River between Austin and La Grange during the Geological Survey of the State of Texas in April of 1889. This year has particular significance because it is the same year that Penrose joined the Geological Society of America. The river has changed in flow regime, and many outcrops have weathered or been flooded. This trip passes through the primarily Claiborne (middle Eocene) geologic section between Bastrop and Smithville, Texas, and illustrates the difficulties to be faced when retracing historic geological surveys. The group will be using and testing a mobile application developed specifically for this field trip theme.