Paleogeographic Setting of the Late Devonian to Early Mississippian Antler Foreland, Eastern Nevada and Western Utah
GOEBEL, KATHERINE A., University of Arizona, Tucson, AZ
Late Devonian through Early Mississippian depositional patterns in eastern Nevada and western Utah reflect transition from passive to collisional margin regimes. The Late Devonian (Frasnian) passive margin sequence (Devils Gate Limestone, Guilmette Limestone) was flexurally warped by thrust loading of the Roberts Mountains allochthon during eastward tectonic emplacement onto the continental margin. Flexural loading produced an asymmetrical downwarp (foreland basin) with concomitant eastward upwarping (forebulge), and still farther east, a symmetrical downwarp (backbulge basin). The foreland basin received minimal clastic input consisting primarily of bedded chert and hemipelgaic claystone (Pine Cone Sequence, Woodruff Formation). Paleocurrent data from the northeast-southwest-trending backbulge basin (Pilot basin) indicate that clastic detritus was derived from the forebulge to the north-northwest. The southern Pilot basin was the site of relatively shallow water carbonate deposition (West Range Limestone). During the Late Devonian (Famennian) and Early Mississippian (early Kinderhook), northern siliciclastic strata prograded over the southern carbonates, and the axis of the Pilot basin migrated eastward in conjunction with migration of the forebulge, foreland basin, and Antler thrust front.
During the Early Mississippian (early Kinderhook), the forebulge migrated rapidly eastward through eastern Nevada and western Utah to produce local erosional surfaces or shoaling-upward sequences. Following the passage of the forebulge, the area subsided flexurally during the late Kinderhookian and became incorporated into the Antler foreland basin. The cratonward edge of the foreland basin was the site of carbonate bank deposition (Joana Limestone). With the foreland basin, west of the carbonate bank, shale and siltstone were deposited and grade westward into hemipelagic clay (Webb Formation).
During the Early Mississippian (Osage), carbonate turbidites (Tripon Pass Limestone) derived from eroded highlands to the east in Utah and to the southeast in southern Nevada were deposited in the foreland trough. Following deposition of the Tripon Pass Limestone the Antler foreland basin was filled by eastward prograding clastics (Chainman Shale, Diamond Peak Formation) derived from the Roberts Mountains allochthon.
AAPG Search and Discovery Article #91009©1991 AAPG-SEPM-SEG-SPWLA Pacific Section Annual Meeting, Bakersfield, California, March 6-8, 1991 (2009)