Petrography of the coarse-grained facies of the Miocene-Pliocene Ringold Formation, south-central Washington State
- Western Washington Univ., Bellingham, WA (United States). Geology Dept.
- Westinghouse Hanford Co., Richland, WA (United States)
The Miocene-Pliocene Ringold Formation in the Pasco Basin of south-central Washington is thought to have been deposited by two major river systems, the ancestral Columbia and the ancestral Salmon-Clearwater. This study was performed to determine the petrographic characteristics of coarse-grained deposits from these two rivers. Sand samples were collected from conglomerates across the Pasco Basin, artificially consolidated with epoxy, thin sectioned, and stained for ease of K-spar and plagioclase identification. Three hundred points were counted per slide using Gazzi-Dickinson point-count methods. Preliminary results indicate that these two ancestral river systems can be differentiated on the basis of plagioclase/total-feldspar (P/F) ratios and to a lesser extent heavy mineral assemblages. P/F ratio for the Columbia River is 0.77 and for the Salmon-Clearwater River 0.53. Heavy mineral assemblages comprise a total of 9% for the Columbia River and 7% for the Salmon-Clearwater. The variety of heavy mineral types within Columbia River samples is consistently greater. QFL and lithic percentages are less diagnostic. QFL mean percentages for ancestral Columbia River samples are 46-31-23 compared to 39-39-22 for the Salmon-Clearwater River. Lithic counts are dominated by mafic volcanics with subordinate sedimentary and metamorphic lithologies.
- OSTI ID:
- 5128874
- Report Number(s):
- CONF-9305259-; CODEN: GAAPBC
- Journal Information:
- Geological Society of America, Abstracts with Programs; (United States), Vol. 25:5; Conference: 89. annual meeting of the Cordilleran Section and the 46th annual meeting of the Rocky Mountain Section of the Geological Society of America (GSA), Reno, NV (United States), 19-21 May 1993; ISSN 0016-7592
- Country of Publication:
- United States
- Language:
- English
Similar Records
Provenance analysis of muddy sandstones
New insights into the origin of late Neogene sediments in the Umatilla Basin, north-central Oregon and south-central Washington