Footwall deformation in the strongly coupled Antler orogenic belt, Nevada and eastern California

The middle Paleozoic Antler orogenic belt in Nevada and eastern California is examined
for footwall deformation below the Roberts Mountains allochthon. The Antler
orogen is characterized by the emplacement of the Roberts Mountains allochthon
over the westernNorth America (Laurentia) passive margin and concurrent shedding
of detritus into the foreland basin developed to the east. Two domains are recognized
in the footwall of the allochthon. First, an eastern footwall belt of thrust duplexes in
lower to middle Paleozoic rocks, exposed through structural and erosional windows,
runs from northeast Nevada diagonally southwestward through Nevada and into
eastern California. Second, this is bordered on the west by a structurally more complex
zone, here referred to as the western high-strain footwall belt, which was characterized
by: 1) greater ductile deformation and lowermost greenschist grade metamorphism;
2) the notable absence or thinning of middle Paleozoic strata caused by
footwall excisement beneath the Roberts Mountains thrust; and 3) footwall structural
highs exposed through the Roberts Mountains allochthon. Both footwall belts of
shortening were fully extant before deposition of the Pennsylvanian regional Antler
overlap sequence rocks. Examples of macroscopic deformation, fabric data, and contact
relations of these deformed rocks are described for critical locations.