On Little Stave Creek, a tributary to Tombigbee River, Alabama, within a distance of less than 3 miles, an early Tertiary section of clays, sands, marls, and limestones totaling 400 feet is exposed. The oldest units are referred to the middle Eocene Tallahatta formation, the youngest to the Mint Spring marl member of the Oligocene Marianna limestone. The faunas are dominantly molluscan, including oyster reefs and, at some levels, a prolific growth of corals. It is believed that the faunas lived on or in mud or sands under continental-shelf or estuarine waters that were as warm as, or warmer than, those of the northern Gulf of Mexico today. Average depths were 40 fathoms or less. Most of the assemblages are somewhat mixed and contain shells that were brought in by bottom currents. There is no strong evidence of reworking except at important contacts such as that between the Lisbon formation and the Gosport sand.

The molluscan faunas north of the Rio Grande and those of theTampico Embayment have been fairly well known for many years. The intermediate faunas between the Rio Grande and the Rio Conchos were untouched until the interest in petroleum investigations was focused on northeastern Mexico. The report is a systematic study of molluscan collections made in the course of the geological field work. Old species are discussed, and new species from the Eocene, Oligocene, and Miocene series are described and figured. An attempt is made to relate them to the faunas of known areas. A few introductory paragraphs have been written on the historical development of the area and on the stratigraphic background.