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 nonradiometric methods that are discussed. Our experiences with some of these techniques are described as well