Prolonged 187Os/188Os excursion implies hydrothermal influence after the Chicxulub impact in the Gulf of Mexico

Abstract

The Cretaceous/Paleogene boundary asteroid impact is recorded globally as a negative ¹⁸⁷Os/¹⁸⁸Os excursion, including in sediments recovered from the IODP-ICDP drilling within the peak ring of the Chicxulub structure in the Gulf of Mexico. The reconstructed marine ¹⁸⁷Os/¹⁸⁸Os curves can be used for global age correlations on the ~10 kyr scale. However, the versatility of Os isotope clock between the proximal and distal sites remains unclear. This paper presents ¹⁸⁷Os/¹⁸⁸Os records from early Paleocene sediments deposited in the Chicxulub impact basin and Mexican sites with biochronological scales. The results for these proximal sites show a recovery timescale of ~700 kyr, which is significantly longer than that of the distal sites (~200 kyr). The interval showing the ¹⁸⁷Os/¹⁸⁸Os decline coincides with the enrichment of hydrothermally-derived Mn, implying that hydrothermal venting at the Chicxulub structure may have played a role in the marine chemistry and ecosystem of the Gulf of Mexico.

Fig. 1. Location map.

a Paleogeographic reconstruction for the K/Pg boundary (~66 Ma) showing the locations of the study site (IODP-ICDP Site M0077) within the Chicxulub impact basin and other pelagic sites reported for Os isotope profiles. This map is redrawn after ref. and ODSN generated at https://www.odsn.de/odsn/services/paleomap/paleomap.html. Note that this paleoreconstruction potentially represents the placement of tectonic blocks at ~66 Ma, but does not reflect sea level at the time of impact. b Geographic locations for the study site and sections within the Gulf of Mexico. Map modified after ref. .

Fig. 2. Stratigraphic profiles of ¹⁸⁷Os/¹⁸⁸Os ratios, HSE concentrations, and Os/Ir ratios of the Paleocene white limestone at Site M0077.

a ¹⁸⁷Os/¹⁸⁸Os ratios represent age-corrected (red circle) and measured (white circle) isotope ratios. b Os and Re concentrations. c Ir and Ru concentrations. d Pt and Pd concentrations. e Os/Ir ratios. Planktic foraminiferal zonations A21 and W11 are from ref. and ref. , respectively. Os/Ir ratios for CI chondrite and upper continental crust (UCC) are from refs. ^–.

Fig. 3. Stratigraphic sections showing age, biozones, lithology, ¹⁸⁷Os/¹⁸⁸Os ratios, and Os and Ir concentrations in the Mexican sections.

a Bochil, b Guayal, c El Mulato, and d La Lajilla sections. ¹⁸⁷Os/¹⁸⁸Os ratios represent age corrected (colored circle) and measured (white circle) isotope ratios. Planktic foraminiferal zonations A21 and W11 are from ref. and ref. , respectively.

Fig. 4. CI chondrite-normalized HSE patterns of Paleocene samples.

a Paleocene white limestones in Site M0077. The dashed line represents the sample from the base of limestone (616.52 mbsf). b Paleocene samples in the Mexican sections. c Paleocene samples from a few cm above the K/Pg impact-induced Complex Clastic Unit (CCU) in the Mexican sections. The HSE patterns of upper continental crust (UCC) are also shown in comparison. HSE concentrations for CI chondrite and UCC are from refs. ^–.

Fig. 5. Comparison of ¹⁸⁷Os/¹⁸⁸Os_i profiles after the K/Pg impact.

a ¹⁸⁷Os/¹⁸⁸Os_i ratios in the Chicxulub impact basin (Site M0077) and distal pelagic sites for ~3.5 million years (myr) after the impact. b ¹⁸⁷Os/¹⁸⁸Os_i ratios of Paleocene (Danian) samples in the Gulf of Mexico. Gray line represents the calculated recovery model of seawater ¹⁸⁷Os/¹⁸⁸Os by ref. .

Fig. 6. Osmium isotope profile and paleoenvironmental change after the impact event.

a Age-corrected (red circle) and measured (white circle) ¹⁸⁷Os/¹⁸⁸Os ratio and Os concentration at Site M0077. b Mn/Al ratio. c P/Al ratio. d Pb/Al ratio. e Relative abundance plots for nannoplankton taxa. f Relative abundance of planktic foraminiferal trophic groups. g The percentage of benthic foraminifera relative to all foraminifera. b, c and d are XRF core scan data reported by ref. . Data of e, f, and g are from ref. and ref. , respectively.