The Impact of Post-Orogenic Erosion and Sediment Transport on the Detrital Zircon Provenance of Incipient Foreland Basins

Abstract

Detrital zircon provenance data indicate that fold-thrust belts and their adjacent foreland basins serve as important sediment sources well after contractional deformation has ceased. Sediments derived from the erosion of old and inactive foreland basins can constitute much of the early-stage infill of foreland basins on the opposite side of a continent. For example, many of the detrital zircons from early Cordilleran foreland basin strata in western North America are derived from eastern North American sources. The Lower Cretaceous (Aptian) McMurray Formation was deposited in the distalmost portions of the Alberta foreland basin and is one of the principal reservoir sandstones of the Athabasca Oil Sands. Despite its relative proximity to the Cordillera fold-thrust belt, detrital zircons in the McMurray Formation indicate a clear Appalachian provenance. Similarly, Jurassic-age eolian sandstones in the southwestern United States contain detrital zircons derived from the Appalachian orogen and foreland basin. The presence of Appalachian-derived detrital zircons in Mesozoic strata of western North America requires that transcontinental fluvial systems transported these sediments from eastern North America long after contraction in the Appalachians ceased. A younger, opposite-directed (west-to-east), episode of post-orogenic sediment transport appears to have occurred in the Canadian Rockies following the cessation of contractional deformation. Detrital zircons from Paleogene-Neogene conglomerates exposed in the Canadian Plains record a major flux of Cordilleran-derived material to the northeast. Precambrian strata in North America record older examples of post-orogenic and transcontinental sediment dispersal. Detrital zircons from the Grenville Orogeny are present in Proterozoic strata throughout North America, including the western United States and the Canadian Arctic. In contrast to this widespread dispersal, detrital zircons derived from the active uplift of the South American Andes are largely sequestered within the proximal foreland basin. The cause of the post-orogenic flux of material is likely associated with isostatic rebound due to erosion of the orogenic load; however, extensional deformation and dynamic (mantle) effects may also play a role. In North America, and likely elsewhere, the result has been periodic transfers of sedimentary material from inactive fold-thrust belts and foreland basins to distal locations.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016