Lower Cambrian bioherms in central Nevada and eastern California
- Univ. of Nevada, Las Vegas, NV (United States). Dept. of Geoscience
The Lower Cambrian stratigraphic sequence in the Ravenswood area of central Nevada, consisting of mixed siliciclastic-carbonate sediments, was formed in a shallow marine and storm-dominated environment. The limestone facies records deposition on a shallow subtidal, open shelf on which developed small isolated patch reefs constructed by archaeocyaths and microorganisms. These patch reefs, generally 5--10 m high and 10--25 m wide in outcrop, grew up on the foundation of bioclastic (brachiopod shells) layer or siltstone, differentiated into boundstone facies and flanked packstone facies, and are surrounded by siliciclastic facies. The Montenegro bioherms in the White-Inyo Mountains of eastern California, 6--8 m high and 25 m wide in the outcrop, consist of many kalyptrae which were stacked together to form a compound reef-like buildup. The bioherms are underlain by a silty, crossbedded argillite and interfingered with siliciclastic facies laterally. Most of the kalyptrae forming the bioherms were built by archaeocyaths bound by calcibionts. Closer inspection shows that each kalyptra (50 cm [times] 20 cm in dimension) is composed of many small lenses which were stacked together and filled by argillite. Both the Ravenswood patch reefs and the Montenegro bioherms represent the earliest preserved archaeocyathid-cyanobacteria carbonate buildups in the western Great Basin. These roughly coeval Lower Cambrian bioherms share many common features. On the other hand, they show some differences in structure, paleoecology, and taxonomic composition of archaeocyaths which evidently reflect the variation of environment from place to place.
- OSTI ID:
- 5098500
- 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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