Dating techniques in fault investigations
Determining the time of most recent fault movement is an important part of assessing a possible site for a nuclear power plant. The purpose of this paper is not to present research information but to provide a practical guide to some of the dating techniques available to the engineering geologist working on nuclear power plant siting. Emphasis is placed on the practical aspects, such as usable minerals, conditions necessary for them to yield correct dates, degree of accuracy, sample collection, sample size, and sample packaging.
In this paper, we have taken for granted the usual geologic field techniques—such as those used in stratigraphy, paleontology, and structural analysis—for assessing fault history. We discuss laboratory techniques used in conjunction with or supplemental to field methods. The specific radiometric methods discussed are 14C (carbon-14), fission track, K-Ar (potassium-argon), thermoluminescense, Rb-Sr (rubidium-strontium), and U-Th (uranium-thorium). Racemization of amino acids, paleomagnetism, and fluid-inclusion techniques are the nonra-diometric methods that are discussed. Our experiences with some of these techniques are described as well.
Figures & Tables
During the “great decade” of siting and construction of nuclear power plants that ended in 1975, the nuclear industry mustered the largest geologic task force in this country’s history, resulting in rapid advances in geologic technologies. Many of the advances are discussed in this volume, a major contribution to engineering geology. Subjects treated are the regulatory, siting, and licensing processes; seismicity of the central and western U.S., with a consumer’s guide to instrumental methods for determination of hypocenters; and techniques, such as remote-sensing, microfacies analysis, dating techniques in faults, trenching as an exploratory method, borehole geophysics, and ground-water studies. Includes a useful glossary.