Antler orogeny

The Antler orogeny was a tectonic event which occurred in Nevada during the Mississippian subperiod of the Carboniferous. A great volume of conglomeratic deposits of mainly Mississippian age in Nevada and adjacent areas testifies to the existence of an important tectonic event, and implies nearby areas of uplift and erosion, but the nature and cause of that event are uncertain and in dispute.

Although it is regarded as an orogeny (mountain building event), some of the classic features of orogeny as commonly defined, such as metamorphism and granitic intrusives, have not been linked to it. In spite of this, the event is universally designated as an orogeny and that practice is continued here. This article outlines what is known and unknown about the Antler orogeny and describes three theories regarding its nature and origin.

A 2023 study attributed the orogeny to sinistral strike-slip faulting along the western edge of Laurentia (the craton equivalent to much of North America). Using strontium isotopes, this study found evidence for a projection ("step") of the Laurentian margin running through what is now central Nevada. This step would have tripped up the major faults, leading to brief convergence and uplift, with the northwestern block of the fault riding up onto the southeastern block. Well-dated unconformities constrain the orogeny to a narrower range of time than typically assumed, starting in the Osagean and ending in the Chesterian regional stages, with maximum exposure and erosion in the Meramecian. In other words, the event began after the Devonian and ended before the Pennsylvanian.