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New approach to time correlation in Proterozoic rocks: sequence boundaries in the Brigham Group, Utah

Conference · · Geol. Soc. Am., Abstr. Programs; (United States)
OSTI ID:6614662
The concepts of depositional sequence analysis, derived from seismic stratigraphy, have been applied to the Upper Proterozoic and Lower Cambrian Brigham Group, an apparently conformable succession of fluvial to shallow-marine quartzite, conglomerate, mudstone, and subordinate volcanic rocks, as much as 5000 m thick, and cropping out in western Utah and southeastern Idaho. Detailed stratigraphic logs and facies mapping in the Wasatch, Sheeprock, Drum, and Canyon Ranges suggest the presence of 4 or perhaps 5 regional unconformities or sequence boundaries. Stratigraphic relations such as onlap and truncation tend to be subtle, and in most places they are distinguished with difficulty from faulted contacts. Most of the sequence boundaries identified correspond with formation contacts, because sequence boundaries cannot be readily detected when underlying and overlying facies are the same; other formation contacts, defined by arbitrary cut-off between laterally intertonguing facies or by gradational changes in the lithology of quartzite, are not a sequence boundaries. The results from the Brigham Group are significant because they suggest a new way of establishing time correlation in unfossiliferous siliciclastic rocks of Proterozoic age. Several samples of felsic tuff have been collected form the Inkom Formation for U-Pb dating of zircon, but the analyses have not yet been completed.
Research Organization:
Columbia Univ., Palisades, NY (USA)
OSTI ID:
6614662
Report Number(s):
CONF-8510489-
Conference Information:
Journal Name: Geol. Soc. Am., Abstr. Programs; (United States) Journal Volume: 17
Country of Publication:
United States
Language:
English