Lower Paleozoic Strata and Alluvial Fan, Death Valley National Park, California
Lower Paleozoic carbonates (limestones and dolomites) and quartzites exposed in the Cottonwood Mountains. The Lower Paleozoic carbonates were deposited in a marine environment in warm seas along the gently sloping western margin of the North American continent. Interlayered with the carbonate rocks are layers of white quartzites, which probably formed in a beach or dune setting.
Death Valley is a classic locality for studying alluvial fans. Alluvial fans form at the base of mountains where streams reach a plain and their gradient and energy are abruptly lowered. In general, the coarser gravels are deposited near the base of slope, while the finer grained sediments are transported farther out on the plain.
During the late 1970' and early 1980's a series of intense rainstorms affected the California Basin and Range. Floods swept across the fans eroding new channels and depositing light-colored rocks (center), which contrast sharply with the older darker parts of the fan with well-developed desert varnish.
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