Dating Methods Applicable to Quaternary Geologic Studies in the Western United States

Miscellaneous Publication 89-7, 1989, 80 pages, $6.75

Radiocarbon dating of terrestrial organic material, S.L. Forman and G.H. Miller
Using dendrochronology to date late Holocene geologic events, D.K. Yamaguchi
Use of soils in estimating ages of Quaternary deposits and faults, P.W. Birkeland
Slope-morphometric dating, M.N. Machette
Thermoluminescence dating of Quaternary sediments, S.L. Forman
Tephrostratigraphy and tephrochronology, R.C. Walter
Applications of K/Ar and 40Ar/39Ar dating to Quaternary geology, R.C. Walter
Amino acid geochronology and paleothermometry: resolution and limitations in carbonate fossils, G.H. Miller

Introduction

A persistent problem in Quaternary studies is determining the timing of climatic, tectonic, volcanic or anthropogenic events as recorded in terrestrial records. The ability to understand regional mechanisms of environmental change is severely limited if an independent chronology cannot be established for disjunct areas. Without a secure geochronology it is not possible to address the causal relationship between changes in the hydrologic, tectonic, climatic and anthropogenic systems.

During the past decade there has been significant advances in geochronology, with the refinement of (e.g., thermoluminescence dating, tephrostratigraphy) and the development of (e.g. accelerator mass spectrometry radiocarbon dating) of many techniques. Many of these methods are currently used to constrain the timing of geological events. However, often the application of these methods and interpretation of results is not straightforward. It is becoming necessary for the field geologist to have a basic understanding of the limitations and requirements of potential dating methods, initially to collect optimal samples for each technique, and subsequently for the judicious interpretation of the results.

The emphasis of this special paper is on the application and limitations of dating methods, concentrating on field aspects pertinent to geologic studies. This miscellaneous paper is a refined text used for a two-day short course in May, 1989 on Quaternary Dating Methods for the Utah Geological and Mineral Survey. Topics covered include: conventional and accelerator mass spectrometry radiocarbon dating techniques, thermoluminescence dating, dendrochronology, amino acid racemization, fission track and K/Ar methods, soil morphology and slope morphometric techniques. These dating techniques are most often used or have the greatest potential for constraining the timing of geologic events in the Basin and Range Province.

Techniques not mentioned in this contribution, but show promise, such as U/Th series dating applied to secondary carbonate, cosmogenic radionuclides, and cation exchange ratio are developmental and not readily available to most geologists.

These papers provide a basic understanding of the principles, potential, problems and limitations of various techniques and will serve as a guidebook into the dynamic world of geochronology.