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Masters Thesis

Characterization of the Indian Springs formation in east-central California

Study of Mississippian-Pennsylvanian boundary strata in east-central California has confirmed that they should be assigned to the Indian Springs Formation, a distinctive unit well studied in southern Nevada. The formation in east-central California comprises cyclic intervals of mixed and unmixed carbonate and terrigenous-derived strata, in addition to phosphate-bearing units, and can be correlated to the Upper Mississippian Indian Springs Formation in southwestern Nevada based on similarities in age, lithology, and stratigraphic position. The stratigraphic sequence comprises platform margin fades that represent deposition near or at the platform edge. The formation rests unconformably on the Visean-age carbonate platform edge fades of the Santa Rosa Hills Limestone or upper Monte Cristo Limestone, and is overlain gradationally by deeper water strata of the Tihvipah Limestone. The Indian Springs Formation represents a period of deposition controlled by sea level fluctuations and storm or ocean current activity, and records deposition of fades that are transitional between emergent siliciclastic shelf strata to the east and southeast of the study area, and deeper water Antler flysch deposits of the Rest Spring Shale (upper Chainman Shale equivalent) to the north and northwest. The identification of brachiopods and conodonts that have been collected from units within the Indian Springs Formation indicates that the formation comprises upper Chesterian- to Morrowan-age strata, and confirms the presence of Lower Pennsylvanian strata in this part of east-central California.

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