The Cretaceous-Paleogene transition in the northern Mississippi Embayment, S.E. Missouri: palynology, micropaleontology, and evidence of a mega-tsunami deposit

Upper Cretaceous to lower Paleogene sedimentary rocks in Southeastern Missouri record the northwest extension of the Mississippi Embayment, yet very little information exists about them due to lack of exposures. Access to borehole and trench material and well logs provided an opportunity to study the sedimentology, palynology and micropaleontology of the three formations spanning the Cretaceous-Paleogene (K-Pg) boundary interval: Owl Creek (Cretaceous) and Clayton and Porters Creek (Paleocene). Lithologic features, palynomorphs (mainly spores, pollen, dinoflagellate cysts), dispersed organic matter, and foraminifera were used to interpret biostratigraphy, paleovegetation, paleoclimatic and depositional conditions, thereby creating a framework upon which further questions involving the K-Pg boundary transition could be addressed. Three hundred and seventy-nine palynomorph taxa have been identified; most are angiosperms and six taxa (one pollen and five dinoflagellate cysts) are potentially new. Seventeen of the 18 foraminifera identified are benthic. These microfossil assemblages contain Late Cretaceous and Paleocene taxa, and confirm a Danian age for the Clayton Formation, which rests unconformably on the Owl Creek. Thus, the K-Pg boundary itself is missing. The characteristics of four distinct graded Clayton units, i.e., basal Coquina Zone containing rip-up clasts with microtektites, reworked Cretaceous macrofossils, microfossils and palynomorphs, Glauconite Zone, Gray Zone, and upper Hardground Zone, and driller\u27s log information suggest that the Clayton Formation was deposited as a single megatsunami following the K-Pg Chicxulub impact event --Abstract, page iii