Late Quaternary geology of small basaltic volcanic centers, SW USA: Disparity among dating methods and implications for volcanic and geomorphic studies
Journal Article
·
· Geological Society of America, Abstracts with Programs
OSTI ID:140009
- Univ. of California, Riverside, CA (United States). Dept. of Earth Sciences
- Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Geology
- Ohio State Univ., Columbus, OH (United States). Byrd Polar Research Center
- Los Alamos National Lab., NM (United States)
Evaluation of volcanic hazards near the proposed high-level radioactive waste repository at Yucca Mountain provides the impetus for a series of detailed field and geochronologic studies of selected small late Quaternary basaltic scoria cones and lava flows in Nevada and California. Two of the most significant results of these studies are: the presence of chronostratigraphic units which indicate multiple eruptions with significant intervals of no activity between events (polycyclic volcanism); and a marked difference between conventional, numerical ages derived from K-Ar and Ar-40/Ar-39 methods and numerical, calibrated, and relative ages derived from thermoluminescence, cosmogenic He-3, the degree of soil development, and geomorphology of these volcanic landforms. Soil-bounded unconformities and buried stone pavements define the boundaries of chronostratigraphic units within these small volume basaltic centers. Volcanic centers displaying this type of stratigraphy may appear morphological simple but cannot be considered mongenetic. Recent studies by Perry and Crowe demonstrate that geochemical variations within a single basaltic volcanic center in NV are consistent with several magma batches forming a complex polycyclic volcano. The K-Ar and Ar-40/Ar-39 ages are 1--2 orders of magnitude older than either TL or cosmogenic He-3 and appear to have insufficient precision to constrain the ages of chronostratigraphic units within polycyclic volcanoes. In contrast, preliminary data indicate the TL and cosmogenic He-3 dating methods have the ability to resolve the late Quaternary volcanic stratigraphy, and results from these dating methods are consistent with the degree of soil development and geomorphic modification of the volcanic units. K-Ar and Ar-40/Ar-39 dates from these small basaltic volcanic centers have been used to calibrate new Quaternary dating methods, e.g. rock varnish, which in turn have been used to interpret landscape evolution in the SW US.
- OSTI ID:
- 140009
- Report Number(s):
- CONF-921058--
- Journal Information:
- Geological Society of America, Abstracts with Programs, Journal Name: Geological Society of America, Abstracts with Programs Journal Issue: 7 Vol. 24; ISSN 0016-7592; ISSN GAAPBC
- Country of Publication:
- United States
- Language:
- English
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