Abstract:
Moscow Landing is a well-known Cretaceous-Paleogene (K-Pg) boundary site located in eastern Sumter County Alabama USA and serves as a natural laboratory to study the end-Cretaceous mass extinction given its proximity to the Chicxulub impact. Unique, discontinuous, sand bodies, commonly known as the Clayton sands, mark the contact between Cretaceous and Paleogene rocks. Megawaves generated by the Chicxulub impact and incised valley filling have been cited as the possible mechanisms behind Clayton sand deposition. To further investigate the source of the sediment in the Clayton sands, a multidisciplinary approach is used that involves microscopy (SEM analysis), geochemistry (trace element and major oxides), and detrital zircon U-Pb geochronology. This work represents the first wherein U-Pb geochronological tools have been applied to a K-Pg site in Alabama. Zircon ages reveal an Appalachian-derived sediment signature, with four grains of ~550 Ma possibly indicating a Chicxulub impact-derived source (i.e. Pan-African in age). Shock features within the zircons were not observed, possibly indicating that the ejecta blanket at Moscow Landing was erased or diluted by the subsequent megawave surge as previous research suggests. In addition, the detrital zircon data presented corroborate previous studies in suggesting that the ancestral Mississippi River system was draining large portions of North America at the end-Cretaceous into the Gulf of Mexico as it does today.
