Antler orogeny it have been tried—east dipping subduction, west-dipping subduction, and strike-slip motion. None of them is without serious problems and the nature and driving force of the orogeny remain uncertain. This much is known concerning the Antler orogeny: Based on stratigraphic relations near Antler Peak, of the Battle Mountains, Roberts introduced the term Antler orogeny in an abstract as follows: "The earliest orogeny, here named the Antler orogeny ... took place during Mississippian (?) and early Pennsylvanian time." That abstract was followed in 1951 by his geologic map of the Antler Peak quadrangle in the text of which he described the
Colorado orogeny Central Plains orogeny. The boundary between the Colorado orogeny and the Wyoming craton is the Cheyenne belt, a 5-km-wide mylonitic shear zone that verges northward. The Cheyenne belt transects and cuts off the south edge of the older Trans-Hudson orogeny. The Paleoproterozoic volcanic and sedimentary rocks that resulted from the Colorado orogeny underwent metamorphism followed by plastic folding under moderate pressure and temperature (PT) conditions (temperature about 500 °C and pressures in excess of 1.2 GPa). The metamorphism was accompanied by intrusion of intermediate calc-alkalic rocks, such as the granodiorites of the Boulder Creek batholith. The accompanying amphibolite facies metamorphism