Earth and Environmental Sciences Poster Session
Academic Level at Time of Presentation
Junior
Major
Chemistry & Geology
List all Project Mentors & Advisor(s)
Gary E. Stinchcomb, PhD; William E. Lukens, PhD
Presentation Format
Poster Presentation
Abstract/Description
This study revisits a Cretaceous-Paleogene (K-Pg) sedimentary section in western Kentucky to determine the nature of this boundary and the depositional environments. Although previous pollen work identified the boundary over four decades ago, to our knowledge no work has been carried out at this important K-Pg boundary site. A combination of stratigraphy and sedimentology were used to characterize the section in detail. Bulk and oriented samples were collected for grain-size, geochemical, and petrographic analysis. We relocated the site and measured 1.5m of section that includes the K-Pg boundary. Four distinct units were identified and from base to top of section are (I) bioturbated black lignitic clay, (II) bioturbated brownish gray mud, (III) gray laminated mud with interlaminated quartz and micaceous sand, and (IV) red and yellow mud with laminated sand. The K-Pg boundary is a 5mm thick Fe-sulfide concretion layer, where these concretions commonly have a mammillary fabric. Preliminary geochemistry shows an iridium anomaly near the boundary. Petrographic analysis shows the presence of deformation features in quartz within the section at the boundary. Fossil wood and amber droplets occur throughout the section. The presence of fossil wood, amber droplets, and root traces below the K-Pg boundary suggest the presence of a paleosol weathering in a marsh environment. Above the boundary, the presence of leaf impressions, along with fossil wood, and cyclic deposition of mud and sand suggests delta plain or prodelta environment. These depositional environments are consistent with the site being situated in a transitional zone along the Mississippi Embayment.
Location
Waterfield Gallery
Start Date
November 2021
End Date
November 2021
Fall Scholars Week 2021 Event
EES Poster Session
Revisiting the Cretaceous-Paleogene boundary in western Kentucky, USA
Waterfield Gallery
This study revisits a Cretaceous-Paleogene (K-Pg) sedimentary section in western Kentucky to determine the nature of this boundary and the depositional environments. Although previous pollen work identified the boundary over four decades ago, to our knowledge no work has been carried out at this important K-Pg boundary site. A combination of stratigraphy and sedimentology were used to characterize the section in detail. Bulk and oriented samples were collected for grain-size, geochemical, and petrographic analysis. We relocated the site and measured 1.5m of section that includes the K-Pg boundary. Four distinct units were identified and from base to top of section are (I) bioturbated black lignitic clay, (II) bioturbated brownish gray mud, (III) gray laminated mud with interlaminated quartz and micaceous sand, and (IV) red and yellow mud with laminated sand. The K-Pg boundary is a 5mm thick Fe-sulfide concretion layer, where these concretions commonly have a mammillary fabric. Preliminary geochemistry shows an iridium anomaly near the boundary. Petrographic analysis shows the presence of deformation features in quartz within the section at the boundary. Fossil wood and amber droplets occur throughout the section. The presence of fossil wood, amber droplets, and root traces below the K-Pg boundary suggest the presence of a paleosol weathering in a marsh environment. Above the boundary, the presence of leaf impressions, along with fossil wood, and cyclic deposition of mud and sand suggests delta plain or prodelta environment. These depositional environments are consistent with the site being situated in a transitional zone along the Mississippi Embayment.