TRACKING DEEP-MARINE ECOSYSTEM RECOVERY AND FORAMINIFERAL TURNOVER ACROSS THE K/PG BOUNDARY

The record of DWAF from the Upper Cretaceous shows high abundance, species richness, and diversity. In the Contessa Highway section, a significant turnover in species composition is observed at the K/Pg boundary. In our record, the species are placed in the extinction, survivor, Lazarus, and new groups. The turnover rate among DWAF is comparatively high at Contessa. However, several species that disappeared from our record at the boundary are known from the Paleocene in other parts of the world, such as Trinidad, IODP Site 1511 in the Tasman Sea, Site 959 on the Côte d’Ivoire Margin, and the Polish Carpathians. The turnover rate observed at Contessa is likely a local response to the K/Pg boundary event, as very few DWAF species became extinct globally at the boundary. Moreover, assuming that some of the taxa listed in the extinction group may reappear as Lazarus taxa higher in the Paleocene is reasonable.

All the samples are from the Contessa Highway section from Maastrichtian and Danian. The lowermost 50 cm of the Paleocene Scaglia Rossa Formation above the K/Pg boundary was collected bed-by-bed and subsequently at a sampling resolution of 10 cm to a stratigraphic height of 1 m. In the lab, samples were first broken into small pieces around 1-2 cm in size. The samples were then dissolved using the dilute hydrochloride acid.

The microfossil data was analyzed by (1) biodiversity: which is the quantitative estimation of the foraminifera diversity in the community based on the collected samples. Ecological analysis plotted the data to inform the trends and indicated the environmental condition pattern. (2) Taxonomy: All the microfossil data was identified based on the deep-water agglutinated foraminifera guide, and the structure community was recorded. (3) Abundance: The relative abundance of taxonomy was fitted. (4) Morphogroups: The general morphology of foraminiferal test related to ecological behavior and paleoenvironmental tools to understand the carbon flux of the seafloor. (5) Faunal turnover rates expressed the species changes during the boundary, how fast and how the species could react at and after the boundary. The recovery of the deep-marine ecosystem is aligned with other micropaleontological researchers that estimate the food web restoration following the K/Pg boundary event.