Submarine gravity slides on the Paleozoic continental slope at the western edge of the Great Basin, east-cental California: A mechanism for development of unconformities in slope environments

The middle Paleozoic continental slope, represented by rocks exposed near Badger Flat in the northwestern Inyo Mountains, at the western edge of the Great Basin in east-central California, failed by submarine gravity sliding twice during Silurian and Devonian time. Each time a major unconformity was developed between the surface exposed beneath the slides and the much younger rocks deposited after the slope failures. The first slope-failure event took place between the late Early Silurian and the end of the Late Silurian when much of the upper member of the Late Ordovician-Early Silurian Ely Springs Dolomite was detached and displaced as a coherent slab ???1 km down slope. The second event occurred in the Middle Devonian when rocks of the Ely Springs Dolomite were again detached, this time forming a rockslide that traveled about 10km down slope to the northwest where it was deposited as a chaotic breccia >250m thick. These events took place as the region was undergoing substantial geomorphic change. The first detachment resulted from an abrupt steepening of the slope, an event previously recognized as having occurred all along the continental margin from eastern California to central Idaho. The second event probably was triggered by a pronounced drop in sea level on the already rather steep slope. At least one similar detachment resulting in an unconformity has been recognized along the middle Paleozoic margin in central Nevada. Recognition of these slope-failure events in an area of unusually complete exposure of middle Paleozoic slope deposits provides an excellent example of a mechanism other than submarine erosion or nondeposition to explain the development of unconformities in ancient slope sequences.