Lake Mead - Quaternary-age caprock

This view is looking north along the edge of a low escarpment of Quaternary-age caprock along one of the tributaries of Echo Wash. The caprock is a fossil desert soil called calcrete (or caliche). Calcrete forms when surface sediments are tightly cemented by calcium carbonate and clay. The cementation process involves cycles of infrequent wetting and subsequent drying of strata, often on an alluvial fan surface. Calcrete is common in areas where local streams flow across carbonate rocks (limestone and dolomite). In this view, the south face of Long Wall Ridge is in the distance. The escarpment consists of Paleozoic-age rock formations, mostly limestone beds of Devonian and Mississippian in age (Beard and others, 2007). This image was taken along the Echo Bay access road about one mile south of the intersection with the Northshore Road.