Antler orogeny

[3] The dark color of the western assemblage, the scarcity of carbonate rocks, and a near absence of shelly fossils, are generally interpreted to indicate a relatively deep-water depositional environment.

[2][3] From an early date,[7] geologists have struggled to explain the presence in Nevada and adjacent areas of the Antler orogenic deposits without achieving a consensus.

The advent of plate tectonic theory provided a variety of possible mechanisms by which the Roberts Mountains thrust and the orogenic deposits could be explained, but none of them has been universally accepted.

As these rocks are unconformably overlain by the Battle Formation of Early Pennsylvanian (Des Moines) age, the orogeny probably took place during the Late Mississippian.

Over a period of 22 years numerous reports relating the Antler orogeny and Roberts Mountains thrust to plate convergence were published in various journals, and because their basic tenets have been widely accepted, they are here termed the conventional theories.

One theory involved closure of a back-arc basin between the western continental margin and a volcanic arc over an east-dipping subduction zone.

Burchfiel and Davis presented the first detailed paper that explained the Antler orogeny and the Roberts Mountains thrust in terms of the subduction aspect of plate tectonics, stating: ... the paleogeography of this part of the Cordilleran geosyncline probably consisted of an offshore island complex separated from the continental slope and shelf by a small ocean basin of behind-the-arc type.

Initial regional deformation within the Cordilleran geosyncline—the Mid-Paleozoic Antler orogeny—was characterized by the eastward displacement (Roberts Mountains thrust) of eugeosynclinal units from within the small ocean basin over miogeosynclinal strata deposited on the continental shelf.

[5] In this scheme, the deep-water aspects of the western facies assemblage are due to sea-level rise in the Cambrian[25][26] rather than displacement from an ocean basin.

[8] The sedimentary effects of the Antler orogeny are well known and well described in many published reports,[2][3][4][27] but the exact nature of that event and the driving force remain unsettled.