Rethinking the “Grenville Flood” of Laurentian detrital zircon: Proximal sources, not continental rivers

Abstract

The widespread presence of Mesoproterozoic detrital zircon in western Laurentia has long been interpreted as evidence for transcontinental river systems transporting sediment from the Grenville orogen. This model asserts that Grenville-age zircon were carried across Laurentia during the Neoproterozoic and Paleozoic, but recent isotopic and provenance data challenge this interpretation. Here, we show that detrital zircon age distributions and Hf isotopic compositions east and west of the Transcontinental Arch remained distinct until the late Paleozoic, inconsistent with repeated sediment mixing by a long-lived transcontinental river system. Instead, multiple Stenian magmatic sources in western Laurentia, including the Llano Uplift, Pikes Peak batholith, and the Southwestern Laurentia Large Igneous Province, provide plausible proximal sources of zircon. Additionally, the Pearya terrane, the northern Yukon, and formerly adjacent Antarctic crust may have contributed detrital zircon to western Laurentia’s sedimentary record. Post-Devonian sediment redistribution may have been accomplished by a combination of fluvial, shallow marine, and eolian processes, or indirect sediment routing. These findings suggest that late Paleozoic processes, rather than a Proterozoic transcontinental river(s), were responsible for distributing Grenville-age zircon across Laurentia. This revised model fundamentally alters the prevailing understanding of sediment routing in deep time and highlights the importance of reevaluating long-assumed geodynamic and provenance frameworks.