Preliminary Results From the Chicxulub Post-Impact Sediments: XRF and Physical Properties Data

Catalina.Gebhardt [ at ]


In spring 2016, joint IODP/ICDP Expedition 364 drilled into the peak ring of the Chicxulub crater, offshore the Yucatan Peninsula, Mexico. A continuous core was drilled (Hole M0077A) and recovered a sequence of Paleogene post-impact rocks, suevites, impact-melt rocks and granitic basement between 505.7 m and 1334.7 m below sea floor (bsf). The Chicxulub crater was formed ~66 million years ago by an impact. This catastrophic event was directly linked to a major mass extinction. For this study, we concentrate on the post-impact sediments (505.7 to 617.3 m bsf; ~48 to ~66 Ma). The main goal of drilling the post-impact section was to study the pace and mode of recovery of life in the ocean after the impact, and to analyze the paleoenvironmental changes across the Paleocene and Eocene. The late Paleocene and Eocene are characterized by a series of transient warming events, so-called hyperthermals that were associated with increased atmospheric pCO2. Here, we present preliminary geochemical and physical properties data from the ~112 m of Paleogene sediments. XRF data show high log (Ca/Ti) values between ~617 and ~598 m bsf (Paleocene and early Eocene), and lower values between ~598 and 505 m bsf. In particular the upper part is characterized by high-frequency fluctuations in log (Ca/Ti) reflecting repeated changes in lithology. These were presumably caused by Milankovitch cycles. Low log (Ba/Ti) values characterize the lowermost part of the record between ~617 and ~610, followed by a gradual increase to higher values, presumably indicating an increase in primary productivity towards the end of the Paleocene. Values remain at this higher level between ~605 and ~540 m bsf. Hyperthermals are characterized by strong positive log (Ba/Ti) peaks, likely pointing at highly elevated primary productivity levels during these short-lived events. Between ~540 and ~505 m bsf, log (Ba/Ti) values are more variable and drop occasionally to values as low as were encountered in the lowermost part. Similar to the log Ca/Ti curve, the log Ba/Ti curve is superimposed by high-frequency fluctuations. These fluctuations are also strongly visible in color reflectance measurements.

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Conference (Poster)
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AGU Fall Meeting, PP23B-1304, 11 Dec 2017 - 15 Dec 2017, New Orleans.
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Gebhardt, C. , Perez-Cruz, L. , Chenot, E. , Christeson, G. , Le Ber, E. , Lofi, J. , Nixon, C. , Rae, A. and IODP-ICDP Expedition 364 Science Party, .. (2017): Preliminary Results From the Chicxulub Post-Impact Sediments: XRF and Physical Properties Data , AGU Fall Meeting, PP23B-1304, New Orleans, 11 December 2017 - 15 December 2017 .

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