Abstract
Sedimentary deposits in Stoddard County, southeastern Missouri, reveal a K-Pg transition sequence represented by the uppermost Maastrichtian Owl Creek Formation and the Paleocene Clayton Formation. The Clayton Formation is characterized by a basal fossiliferous coquinite that contains reworked late Maastrichtian macrofossils. Dinoflagellate biostratigraphy is used to determine the age of the coquinite layer and specifically whether or not it is an end-K tsunamite deposit resulting from the Chicxulub impact event. Results indicate a mixed assemblage of late Maastrichtian and early Danian dinocysts within the basal coquinite of the Clayton Formation. Maastrichtian dinocyst taxa identified are Riculacysta amplexa, Pierceites pentagonus, Phelodinium tricuspe and Dinogymnium sp. and dinocysts utilized as global indicators of the basal Danian, also present in the coquinite, consist of Senoniasphaera inornata, Carpatella cornuta, Damassadinium californicum, and Lanternosphaeridium reinhardtii. A gray mud occurring above the coquinite in the middle of the Clayton Formation contains the mid-Danian dinoflagellate Senegalinium iterlaaense. Collectively, these data suggest that the coquinite was deposited well after the K-Pg event but before the middle Danian. The mixed assemblage of Late Cretaceous and Paleocene dinocysts preserved in the coquinite weakens the hypothesis that it is an end-K tsunamite deposit and suggests instead that it may result from a long-term transgressive lag. We also extend the stratigraphic range of the Paleocene Senegalinium simplex downward into the uppermost Maastrichtian.
Highlights
The Mississippi embayment is a long, narrow basin located between the Appalachian Highlands and the Ozark Plateaus (Figure 1)
The Supplementary lists the 87 marine dinoflagellate and acritarch taxa that were identified, counted from our site. We extracted from this total data set 17 taxa based on the utility of their geologic ranges in timing events at the end of the Cretaceous, and arranged the selected taxa into three groups: Late Cretaceous taxa (4 species); Paleocene taxa (10 species); and short ranging known to contain the Cretaceous-Paleogene (K-Pg) boundary-crossing taxa
We believe that this adjustment of the age of the K-Pg boundary downward will adjust the absolute ages determined by Williams et al [68] of Senoniasphaera inornata, Damassadinium californicum and Carpatella cornuta, but this does not alter the observations of these authors that the first occurrence (FO) of S. inornata, and subsequent FOs of D. californicum and C. cornuta takes place after the K-Pg boundary event
Summary
The Mississippi embayment is a long, narrow basin located between the Appalachian Highlands and the Ozark Plateaus (Figure 1). Preserved in the Mississippi Embayment are sediments that were deposited within an early Late Cretaceous epeiric sea that invaded the continent as a result of regional subsidence [1]. Sedimentary deposits near the head of the embayment range from Cretaceous to Quaternary in age [2,3,4] and in some localities are known to contain the Cretaceous-Paleogene (K-Pg) boundary interval [5,6,7]. Missouri near the towns of Bloomfield and Bell City. Global coordinates of study site: 36°55'15" N; 89°52'2" W
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