Lower Cambrian sedimentary Grand Cycle A in northwestern Canada and southern Nevada-southeastern California
- Geological Survey of Canada, Ottawa, Ontario (Canada)
Grand Cycle A is herein restricted by raising the base to a level just above the base of the Sekwi Formation. In ascending order, Grand Cycle A shares the following features in northwestern Canada and southern Nevada-southeastern California: (1) an initial transgression with reduced clastic size, lack of appreciable limestone, and an abrupt faunal change at the Fallotaspis-Nevadella Zone boundary, (2) gradual increase of limestone that is platy and deposited below wave base, (3) biotherms with archaeocyathids or algal buildups, (4) thick succession of shallow water limestone, (5) an abrupt termination of Grand Cycle A at the top of the thick limestone succession. The boundary between the Nevadella Zone and the Bonnia-Olenellus Zone may be at the top of Grand Cycle A or a short distance above in the basal clastics of Grand Cycle B. Grand Cycle A is not considered to be a typical grand cycle, but rather a hybrid that straddles a thermal change. Below are the large, cold water cycles of the Windermere Supergroup. There the clastic half-cycles represent transgression and the carbonate half-cycles regression. Above Grand Cycle A, are warm water, true grand cycles where clastic half-cycles represent regression and the carbonate half-cycles transgression. In Grand Cycle A, both halves represent transgression, with the upper half being a typical warm water limestone.
- OSTI ID:
- 5129861
- 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
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