Paper No. 8
Presentation Time: 9:00 AM-6:30 PM


CEPEDA, Joseph C., Department of Life, Earth and Environmental Sciences, West Texas State Univ, PO Box 60162, Canyon, TX 79016-0001,

The concept of a geologic formation forms the basis for most of what is taught in a Field Geology course. Geologic formations also provide the most useful framework for stitching together the myriad concepts discussed during the course. The concept of formations as stratigraphic units is also an integral part of a field course because formations are the common thread for all the major projects of the course – measured sections, geologic mapping, and regional geologic reconnaissance. Although most of the ideas described below can be applied to all types of formations, the principal focus is on sedimentary rock units.

A comprehensive study of a geologic formation includes looking at, and describing the formation in the field as well as library or internet research on the unit. This provides the student the opportunity to learn or review rock types and lithologies and how formations may change lithologies along strike or down dip. The formation name provides information about the geographical nomenclature of the region. Review of the geologic literature gives information on the geologist(s) that first described the unit and the relative ages of geologic exploration. For example, most geologic formations in the Texas Panhandle were described in the 1890’s or early 1900’s. However, in the Four Corners region, and in most of the American West the first comprehensive geologic surveys occurred in the late 1860’s or 1870’s.

Additional concepts to be discovered by an in-depth study of a formation are the areal distribution of the unit and an understanding of the paleogeography during deposition as interpreted from the fossil assemblage, sedimentary structures and changes in lithology,

Formations also provide the opportunity to introduce the use of other geologic techniques, including paleomagnetism, radiometric dating, and ore deposits. An example of the latter is the widespread mines and prospect pits dug into the Chinle Formation of the Four Corners area during the periodic uranium booms in the region.

The study of individual formations in the field and in the geologic literature provide a thorough review and test of an undergraduate geologic education and an appropriate teaching tool for all aspects of field geology.