Detrital Zircon Geochronology of the Bighorn Dolomite, Wyoming, USA: Evidence for Trans-Hudson Dust Deposition on the Western Laurentian Carbonate Platform

摘要

This study uses detrital zircon U-Pb geochronology from shallow-water carbonates of the Bighorn Dolomite in Wyoming, USA, to provide robust evidence for long-distance eolian sediment transport during the Ordovician. The Bighorn Dolomite was deposited in a shallow-water carbonate platform that developed approximately 10 degrees south of the Ordovician paleoequator on the western edge of Laurentia. The ages and textures of detrital zircons from the Bighorn indicate that the grains were transported by winds through saltation and suspension from the paleo east where rocks of the Paleoproterozoic Trans-Hudson orogenic belt were exposed in present-day Manitoba and Saskatchewan. Our interpretation of long-distance eolian transport is consistent with the paleogeography of Laurentia and expected prevailing wind directions and draws on modern analogs where Saharan sediment is transported by trade winds for distances of more than 3000 km.