This paper presents a discussion of the Lower Claiborne of East Texas to show the different divisions of this group, old names of formations being re-defined and such new names being added as have been found necessary to meet present-day thought.

Mount Sylvan salt dome is in the western part of Smith County, Texas. The existence of a dome was verified by the seismograph, and later detail surface work has likewise shown the presence of a dome in this area, although no drilling has been done to date.

The writers discuss the structural features accompanying the formation of this dome, which are believed to be the result of salt movement into the core. Similar conditions have been observed in other domes in the East Texas district. It is probable that the original salt bed is more than 1,000 feet in thickness and 10,000 feet or more below the surface. It is believed that the salt movement originated along points of weakness. This initiating movement, plus isostatic pressure, and the downward push of a settling basin, causes the upward movement of the plastic salt. The domes occur in local synclinal areas in the East Texas geosyncline, and are commonly flanked by well-developed rim synclines. The rim synclines are probably caused by settling, influenced by a thinning of the original alt series by movement into the stock.