STYLE AND SPATIAL DISTRIBUTION OF THE C5 UNCONFORMITY (DESMOINESIAN) IN EASTERN NEVADA: IMPLICATIONS FOR THE DESTRUCTION OF THE ELY BASIN AND INITIATION OF THE HOGAN BASIN

In eastern Nevada, where present, the C5 unconformity represents a hiatus of late Atokan to middle Desmoinesian, as determined from fusulinacean and conodont data. This boundary is characterized by an abrupt change from shallow water carbonates of the Ely Limestone to deeper water silty micrites and micritic siltstones of the Hogan Formation. In the Central Pequop Mountains and at Buck Mountain, the C5 unconformity is also associated with sub-unconformity structures consisting of small scale thrusts (displace strata 10’s meters), faults of undetermined geometry, outcrop scale open to tight folds and fault propagation folds. In both locations, these structures are abruptly overlain by and do not penetrate the overlying middle Desmoinesian Hogan Formation and demonstrate a NW-SE axis of vergence. The structural disruption of the underlying Ely Limestone shallow carbonates and renewed deposition of the deeper water Hogan Formation suggests that the C5 unconformable surface represents the tectonic culmination of the Ely basin and the initiation of deeper water sedimentation of the Hogan basin.

The geographic distribution of the C5 unconformity suggests, within eastern Nevada, that three NW-SE trending structural highs were juxtaposed against regions of continuous deposition in the early Desmoinesian. Timing of the C5 unconformity and sub-unconformity architecture suggest it may be genetically related to the Ancestral Rocky Mountain tectonics documented in Colorado and Utah.