Abstract

The Upper Cambrian Whipple Cave Formation and Lower Ordovician lower House Limestone of eastern Nevada contain algal stromatolites, flat-pebble conglomerate, lime grainstone, and other carbonate rocks inferred to represent shoal-water depositional environments. Coeval parts of the Hales Limestone, 170 km to the west, consist of dark-colored lime mudstone and wackestone interbedded with coarse-textured alloch-thonous gravity-flow and slump deposits interpreted to have formed in a deeper water slope environment.

The Whipple Cave Formation and some allochthonous gravity-flow deposits of the Hales Limestone contain trilobite genera typical of the North American Faunal Province, whereas in situ deeper water limestones of the Hales contain trilobite taxa that are widespread in northwestern and southern China.

An abrupt biofacies change between shelf and deeper water sites may be analogous to major changes with depth shown by Holocene marine isopod crustaceans in low latitudes, where the permanent thermocline is a major barrier to faunal dispersal. Thus, caution should be exercised in using faunal resemblance data for early Paleozoic plate-tectonic reconstructions unless the habitat and marine climatic preferences of the faunas are known.

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