Since the days of R. T. Hill (1901) two Upper Cretaceous lithic units have been used as formations but have remained unnamed. These two units have usually been called the "Lower Taylor Marl” and the “Upper Taylor Marl.” If Taylor is used as a group, both of these formations belong in the Taylor Group.

In the past 100 years, more than 100 names have been used to designate parts or all of the outcropping Midway and Wilcox rocks in the Gulf Coastal Plain; less than half of these names are used currently by Coastal Plain geologists, and the validity of some of the remaining named rock units has been questioned in certain recent studies. A compilation of these names shows the development of present-day terminology.

Minerals play a vital role in the economy of an industrial State. In Texas, where annual production of minerals currently amounts to more than $4. 5 billion--twice the value of agricultural products, equal the value of manufactured products, and equal to half the value of all retail trade--mineral production is the principal part of the State's economic foundation. Analyses of past production trends and economic factors allow predictions of future trends in this vital and important segment of the Texas economy.

At five places along the outcrop of the Wellborn Formation in Lee and Burleson counties, Texas, anomalously high gamma radiation is associated with concentrations of heavy minerals. The most abundant heavy minerals are ilmenite, magnetite, and zircon. The radiation is emitted by some radioactive element in zircon. The intensity of the radiation and the areal extent of the radiation anomalies were measured by a scintillation counter.