DOI: 10.25921/g1wy-1d88
title: NOAA/WDS Paleoclimatology - Gulf of Mexico and Caribbean XRF Core Scan Data from the Early Paleocene

description: The global heterogeneity in export productivity after the Cretaceous-Paleogene (K-Pg) mass extinction is well documented, with some sites showing no change on geologic timescales, some demonstrating sustained decline, and a few showing a somewhat surprising increase. However, observational data come from sites so widespread that a key outstanding question is the geographic scale of changes in export productivity, and whether similar environments (e.g., open ocean gyres) responded similarly or whether heterogeneity is unrelated to environment. To address this, we developed three new Ba/Ti export productivity records from sites in the Gulf of Mexico and Caribbean which, combined with published data from a fourth site in the Chicxulub Crater itself, allow us to reconstruct regional changes in post K-Pg export productivity for the first time. We find that, on a regional scale, export productivity change was homogenous, with all four sites showing a ∼300 kyr period of elevated export production just after the boundary, followed by a longer period of decline. Interestingly, this interval of elevated export production appears to coincide with the post K-Pg global micrite layer, which is thought to at least partially have been produced by blooms of carbonate-producing cyanobacteria and other picophytoplankton. Global comparison of sites shows that elevated export productivity appears to have been most common in oligotrophic gyres, which suggests that changing plankton ecology evidenced by the micrite layer altered the biological pump, leading to a temporary increase in export production in these settings.
description: Cores were scanned on an Avaatech XRF Core Scanner at the IODP Gulf Coast Repository in College Station, TX, at two excitation conditions focused on different element groups. The first scan was at 10kVp with no filter to analyze major and minor elements (Al, Si, K, Ca, Ti, Mn, Fe, Cr, P, S, and Mg) and the second was at 50kVp with a Cu filter to analyze heavier trace elements (Sr, Rb, Zr, and Ba). Scan resolution was set depending on relative distance above the Cretaceous-Paleogene boundary, based on low resolution shipboard biostratigraphy. Core sections within planktic foraminifer zone Pa or the lower part of zone P1a (very roughly, within ~ 500 kyr of the boundary) were scanned at 1 or 2 cm steps, and sections deposited below the boundary and >500 kyr after the boundary were scanned at 5 cm steps. Some steps were skipped or moved based on visual examination of the core before scanning (e.g., to avoid cracks or uneven surfaces). Laboratory standards were run at the beginning and end of each day to monitor instrumental performance. Raw spectrum data were processed into peak areas in the lab using the software program bAxil. The data archived here have not been quality controlled. For more information on methodology and XRF theory, see https://sites.google.com/scientific-ocean-drilling.org/xrf-iodp/home
     Provided Keywords: Cretaceous, Paleogene, Danian, K-Pg, Export Productivity, Paleoproductivity, Extinction, Chicxulub, Gulf of Mexico, Caribbean, DSDP, ODP