1. Intense Changes in the Main Source of Organic Carbon to the Gulf Coastal Plain Following the Cretaceous‐Paleogene Boundary.
- Author
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Sosa‐Montes de Oca, C., Witts, J. D., Lowery, C. M., Kearns, L. E., Garb, M. P., Naujokaityte, J., Myers, C. E., Landman, N. H., and Pancost, R. D.
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CRETACEOUS-Paleogene boundary ,COASTAL plains ,ALGAL communities ,PALEOGENE ,MARINE phytoplankton ,MASS extinctions - Abstract
To explore both environmental change and the response of non‐fossilizing phytoplankton across the Cretaceous‐Paleogene (K‐Pg) boundary mass extinction event, we determined changes in organic matter (OM) sources using a range of apolar (n‐alkanes, acyclic isoprenoids, steranes, and hopanes) and polar (BIT index) biomarkers. We analyzed two K‐Pg proximal sections, located in the Mississippi Embayment, Gulf Coastal Plain (USA), covering ∼300 kyrs prior to and ∼3 myrs after the K‐Pg event. The OM abundance and composition changed dramatically across the boundary. The post‐impact ejecta layer and burrowed unit are characterized by an increase in the mass accumulation rate (MAR) of plant and soil biomarkers, including high‐molecular‐weight n‐alkanes and C29 steranes as well as the BIT index, related to an erosive period which transported terrestrial OM to the ocean in the aftermath of the impact event. At the same time, MARs of putative aquatic biomarkers decrease (low‐molecular‐weight n‐alkanes, C27 steranes and pristane and phytane), which suggests a collapse of the marine phytoplankton community. The increase of terrestrial OM to the ocean, during the first 280 kyrs after the Chicxulub impact event, is a combination of reworked kerogen, soil and some plant material. Crucially, within the latter part of this erosion period, only ∼160 kyrs after the K‐Pg do biomarkers return to distributions similar to those in the upper Cretaceous, although not to pre‐impact MARs. Thus, our results suggest a long‐term interval for the full sedimentary and ecological recovery of the non‐fossilizing phytoplankton community after this event. Plain Language Summary: The Cretaceous‐Paleogene (K‐Pg) boundary coincides with the latest of the five major mass extinctions in Earth's history. Determining the nature of the associated rapid environmental change and biotic recovery is critical for knowing the cause and effects of this key event and contributes to our understanding of the ongoing biodiversity crisis. We analyzed biomarkers (molecular fossils) in two K‐Pg sections in the Gulf Coastal Plain (USA) near the impact site, covering ∼300,000 years prior to, and ∼3,000,000 years after the K‐Pg event. The organic matter (OM) abundance and composition changed dramatically after the impact event. In particular, an increase in the concentration of plant and soil biomarkers occurred in the first 280,000 years after the impact and is attributed to an erosive period which transported OM from the land to the ocean. At the same time, the concentrations of marine algal biomarkers decrease, suggesting a collapse of the marine algal community. About 160,000 after the K‐Pg event, marine biomarkers return to distributions similar to those pre‐impact. This suggests an initial recovery of algal communities on the Gulf Coastal Plain, although they never recover to pre‐impact abundances during the studied interval (∼3,000,000 after impact). Key Points: Intense erosive regime after the K‐Pg boundary, coincident with collapse of the marine phytoplankton community on the Gulf Coastal PlainInitial recovery of non‐fossilizing algal communities started ∼160 kyr after the K‐Pg event although with lower mass accumulation rates than pre‐impactSedimentary conditions never return to their pre‐impact state, suggesting a long‐term perturbation to the system [ABSTRACT FROM AUTHOR]
- Published
- 2024
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