One megacycle and numerous minicycles are recorded in the stratigraphic interval comprising the Dunderberg Shale and overlying Halfpint Member of the Upper Cambrian Nopah Formation in southeastern California and southern Nevada. The retrogradational leg of the megacycle is expressed by the succession: Bonanza King Formation (peritidal carbonate strata), Dunderberg Shale (outer ramp to peritidal shales and interbedded carbonates), and lower Halfpint (subtidal carbonates). The progradational leg is developed within the Halfpint, above the shale-carbonate boundary, as peritidal cryptalgal boundstone overlying subtidal shelf micrites and pelmicrites. Biostratigraphic data suggest this cycle is the result of regional transgression-regression. The Dunderberg-Halfpint contact, r presenting the boundary between shale and carbonate half-cycles within an apparent grand cycle, does not reflect a major shift in depositional environments, but rather the availability of terrigenous mud and the delicate nature of the carbonate "factory." The main environmental shift occurred during later deposition of the Halfpint carbonate lithosome when a peritidal algal thrombolite complex prograded seaward (see figure).

Coarsening-upward, meter-thick minicycles are abundant in peritidal and shallow subtidal facies in the Spring Mountains and Goodsprings, Nevada district and less common in more distal, deeper, outer ramp facies west of the Spring Mountains. Shallow-marine minicycles are expressed as micrite or shale, and occasionally cryptalgal boundstone, overlain by bioclastic packstone and grainstone as well as intraclastic beds. Deeper subtidal minicycles are expressed as bioclastic wackestone overlying shale or micrite. The minicycles are the products of fair weather-storm cyclicity on the open, deep to shallow subtidal ramp, as well as tidal influences within a peritidal algal-bank complex; as such they do not represent shallowing phases and shifting environments, but rather fluctuating conditio s within their respective environmental settings.

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