Competing Models for the Timing of Cryogenian Glaciation: Evidence From the Kingston Peak Formation, Southeastern California
- Author(s): Mrofka, David Douglas
- Advisor(s): Kennedy, Martin J.
- et al.
The Neoproterozoic (~750-635 Ma) Kingston Peak Formation, southeastern California, is a coarse-grained siliciclastic interval, with laterally extensive carbonate marker horizons, deposited in extensional basins between two regionally extensive carbonate intervals.
Thirty sections measured and two geologic maps produced show a wedge-shaped geometry unique to extensional settings and clarify the conformable relationship between the coarse-grained deposits and the overlying Noonday Dolomite. Carbonate intervals were sampled extensively to determine the value of chemostratigraphic correlation in this interval. A newly mapped regional unconformity near the base of the formation serves to separate the overlying tectonic sequence of the Kingston Peak Formation from the underlying deposits related to the platformal Beck Spring Dolomite. A glacigenic influence is inferred based on the presence of striated clasts in one of several basins, facilitating global correlation with similar coarse-grained deposits thought to record the Earth's most severe ice age.
The Kingston Peak Formation provides a rare example of ancient glacial successions in which the relationship between the sedimentary packaging in vertical and lateral dimensions is apparent in outcrop. This allows the influence on stratigraphic development by the series of tectonic and climate events to be reconstructed without relying on regional or global correlation. These relations show the progressive development of extensional basins from northwest to southeast in the Death Valley region. The exceptional exposure in this region reveals bounding synsedimentary faults allowing tectonic and climate influence on coarse-grained facies to be resolved as well as the lateral persistence and stacking of course grained units. Through-going carbonate marker beds recording regional sea level rise provide timelines allowing the reconstruction and relative timing of climate and rifting events. These relations identify that the Kingston Peak Formation records a complicated regional history in which the record of rifting and climate are intimately related through fault subsidence and the creation of accommodation space.
The availability of accommodation space from tectonism biases the sedimentary record of climate change. Glacial deposits are not necessarily uniquely timed with glacial conditions, but with preservational conditions. This interplay between tectonism and related coarse-grained deposits obscures both the timing and extent of similar coarse-grained deposits related to glaciation.