ABSTRACT: Flexural Controls on the Stratigraphic Evolution of the Antler Foreland, Nevada and Utah

GILES, K. A., Exxon Production Research, Houston, TX, and W. R. DICKINSON, University of Arizona, Tucson, AZ

Stratigraphic relationships within the Late Devonian to Early Mississippian Antler foreland of eastern Nevada and westernmost Utah suggest that lithospheric flexure was the primary control on the geometry and distribution of stratigraphic packages. Stratigraphic relationships attributed to lithospheric flexure include: (1) out-of-phase relative sea level trends and (2) regional-scale inversion of topography.

Loading of the lithosphere by eastward thrust emplacement of the Roberts Mountains allochthon (RMA) over the North American craton from Late Devonian to Early Mississippian time resulted in flexural warping of the craton into a series of northeast-southwest-trending flexural features: an asymmetric downwarp (foreland basin), a cratonward upwarp (forebulge), and even further cratonward, a broad, shallow downwarp (back-bulge basin). Sedimentary packages associated with the flexural features display out-of-phase relative sea level trends. Deposits associated with downwarped areas show either deepening-upward or relatively thick stratigraphic sequences compared to upwarped areas that may show shoaling upward sequences, relatively thin depositional packages, or ultimately unconformity surf ces.

The flexural features migrated eastward in response to continued eastward thrust migration of the RMA. Migration of the flexural features resulted in regional-scale inversion of topography. Former topographic highs (forebulge area) were downflexed and incorporated into the cratonward limb of the foreland basin. Conversely, former topographic lows (back-bulge basin) were uplifted as the forebulge migrated through. The sedimentological signature of the inversion of topography preserved in the Antler foreland strata permits delineation of the position and geometry of flexural features during the transition from passive to collisional margin regimes.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)