Elevated Post K-Pg Export Productivity in the Gulf of Mexico and Caribbean
Abstract
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.Plain Language SummaryPrimary producers are the base of the food chain; this group was severely damaged by the environmental effects associated with the Cretaceous-Paleogene mass extinction. Determining how primary production recovered after this calamity is an important foundation for understanding how ecosystems recovered. Most previous work has focused on a process called export production, whereby organic carbon produced by phytoplankton is transferred to the ocean interior (some of which sinks to the seafloor and is buried). This work has shown that although most parts of the ocean recorded a decline in export production after the extinction event, some regions actually showed an increase. However, it was not clear on what geographic scale these differences occurred, or what caused them. We generated three new records of export production from a single region, the Gulf of Mexico/Caribbean Sea, and found a consistent increase in export production at each site for the same period of time after the extinction event. Comparison with other sites with increased export production shows that many are from open ocean gyres, suggesting that these regions were predisposed to increased export production in the earliest Paleocene because they were characterized by low productivity prior to the extinction.Key Points Post K-Pg export productivity was elevated across the Caribbean-Gulf of Mexico region for ∼300 Kyr At sites with a clearly defined micrite layer, the end of micrite deposition coincides with the top of the highest productivity interval Elevated post K-Pg export productivity appears to be a feature of oligotrophic low latitude open ocean sites
- Publication:
-
Paleoceanography and Paleoclimatology
- Pub Date:
- September 2022
- DOI:
- 10.1029/2021PA004400
- Bibcode:
- 2022PaPa...37.4400L
- Keywords:
-
- Earth Sciences