Provenance of Upper Cretaceous to Paleocene strata in the Alberta foreland basin using detrital zircon U-Pb geochronology and (U-Th)/He thermochronology double dating

Abstract

Flexural foreland basins hold sedimentary records of paleoenvironment and hinterland erosion, making them useful for reconstructing the evolution of orogenic systems. The Turonian–Coniacian Cardium to Paleocene Paskapoo formations have been described in terms of their sedimentary facies and paleoenvironments, but the relationship to fold-thrust belt shortening is contested. Geochronology and low-temperature thermochronology datasets allow us connect Alberta foreland basin strata to tectonic and eustatic events. Here, we present a 1780 meter measured stratigraphic section and new detrital zircon U-Pb geochronology ages and (U-Th)/He thermochronology (ZHe) dates from Turonian–Coniacian formations. Turonian–Campanian sandstones interrupt marine shales and yield ZHe date populations that young up-section (Cardium Fm, ~148 Ma and ~319 Ma; Marshybank Fm, ~124 and ~278 Ma; Chinook Mbr, ~74 and ~139 Ma), reflecting progressive erosion into the fold-thrust belt. U-Pb ages indicate a Proterozoic-Ordovician fold-thrust belt source in the Turonian, and a shift to a more easterly Devonian-Triassic fold-thrust belt source in the Coniacian–Campanian, corresponding to punctuated transpression in the distal fold-thrust belt. Campanian–Paleocene sandstones record deltaic–nonmarine environments and fold-thrust shortening known as the “Rundle Pulse.” These units share age spectra indicating a dominant Neoproterozoic–Ordovician fold-thrust source, supporting unroofing of new sources following proximal uplift. ZHe date populations become older moving up-section in the Maastrichtian–Paleocene (Coalspur, ~59 Ma and ~187 Ma; Paskapoo, ~152 and ~226 Ma), reflecting foreland basin cannibalization. Reconstruction of the Alberta foreland basin clarifies sedimentary responses to climate, distal pulses of transpression, and fold-thrust belt shortening.