Abstract

A thin persistent unit (maximum thickness 13 m) of probable Cambrian age in the Chino Valley region of northwestern Arizona consists of three laterally equivalent, mutually exclusive lithofacies. These are, from west to east, lithic sandstone, pebble to boulder conglomerate, and dolomite. The unit, named the Chino Valley Formation, is younger than middle Middle Cambrian and older than Devonian in age. A Late Cambrian age is probable, although no fossil evidence supports this conclusion.

The lithic sandstone and conglomerate facies were derived from two apparently active source areas and were probably deposited in shallow marine water. Uplift to the south or southwest of the area almost reversed the regionally westward-dipping Cambrian paleoslope and exposed sedimentary rocks to erosion. Sediment derived from this terrain formed the lithic sandstone facies. Synchronous movement initiated erosion of the Mazatzal Quartzite (Precambrian) from which the conglomerate facies was derived. The dolomite facies is inferred to have accumulated on a mud flat in the supratidal zone.

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