APPLYING NEW GEOCHEMICAL PROXIES TO THE STUDY OF THE CRETACEOUS-PALEOGENE IMPACT-GENERATED TSUNAMIS: MUSSEL CREEK, ALABAMA

The application of geochemical proxies to detect paleo-tsunami deposits is a relatively new frontier that has never before been utilized to study the Cretaceous-Paleogene (K-Pg) Boundary of the Gulf of Mexico. The Chicxulub Impact has been identified as the primary catastrophe leading to the K-Pg Mass Extinction. This impact set off a chain of global events that included megatsunamis. The Gulf of Mexico K-Pg Boundary locations hold importance due to being proximal to the impact. Our study site, the Mussel Creek outcrop in Lowndes County, Alabama, is particularly understudied. Mussel Creek was situated in shallow marine conditions during the end-Cretaceous. It contains distinct features, including thick sand and conglomerate beds, that are hypothesized to have been created from megatsunamis induced by the Chicxulub Impact.

Tsunami deposition in offshore locations is understudied, but may exhibit better preservation than onshore deposits. However, offshore beds are notoriously difficult to specifically attribute to tsunamic origin. We have collected preliminary geochemical data from Mussel Creek, including terrigenous biomarkers and PAHs, to understand the autochthonous vs. allochthonous inputs. We will also apply classical tsunami proxies, including analyses of grain size and heavy detrital minerals.

In order to evaluate the origin of Mussel Creek’s beds, we are trying to ascertain if the oyster shells are autochthonous in a fossiliferous bed that has been proposed as a likely tsunamiite. We are using two experimental approaches to answer this question by measuring Nd and Sr isotopes with thermal ionization mass spectrometry. We will apply ¹⁴³Nd/¹⁴⁴Nd as a water mass tracer to determine if the oysters grew largely in place in the bed, or if they were conveyed to the site from a notable distance. Additionally, we will compare the shells’ ⁸⁷Sr/⁸⁶Sr to that of the global seawater curve at the K-Pg Boundary, since a deviation from the expected value may indicate that they could have been transported or reworked by a tsunami.