Crustal structure and subsidence mechanisms of the Williston Basin: New constraints from receiver function imaging

Abstract

Mechanisms responsible for the long-term subsidence of intracontinental basins such as the Williston Basin in North America remain enigmatic, partly due to the thick sedimentary layer commonly found in the basins that prevents reliably imaging the deep crustal and upper mantle structures using some of the most-commonly employed seismic methods such as receiver function analysis. In this study, we used receiver functions recorded by 274 USArray and other stations in the Williston Basin and adjacent areas to investigate the layered structure of the crust in the hydrocarbon-rich intracontinental basin. After the removal of strong reverberations on the receiver functions associated with a low-velocity sedimentary layer using a recently developed time-domain deconvolution approach, two positive arrivals representing downward increases of seismic velocities are imaged beneath the basin and the area to the west. The top interface has a depth of about 40 km at the depocenter of the basin, and gradually shallows eastward to about 30 km beneath the Superior Craton, and the deeper interface has a mean depth of about 65 km beneath the Williston Basin. The layer between the two interfaces may represent an eclogitized or garnet-rich lower crustal layer. The results are consistent with the hypothesis that continuous retrograde metamorphic reactions in the previously-thickened lower crust during the Paleoproterozoic Trans-Hudson Orogeny resulted in the subsidence of the intracontinental Williston Basin.