The Cambrian deposits of the western United States represent three major coexisting lithofacies, arranged more or less parallel with the western margin of the continental interior. The inner lithofacies is composed largely of terrigenous materials derived from the continental interior. The middle lithofacies consists largely of clean carbonate sediments of many kinds that represent relatively shallow, commonly high-energy deposits interpreted to be the products of a great series of coalescing banks. Seaward from the carbonate belt is an outer lithofacies represented by generally dark-colored, apparently deeper water sediments containing a moderate to high proportion of siliceous materials, some of apparent terrigenous origin. Region-wide expansion and contraction of the c ean carbonate environment, and overall temporal transgression of all environments toward the continental axis, have produced the complex of formations and formational sequences presently observed in the western United States.

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