JpGU-AGU Joint Meeting 2017

Presentation information

[JJ] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS22] [JJ] Drilling Earth Science

Thu. May 25, 2017 9:00 AM - 10:30 AM IC (International Conference Hall 2F)

convener:Yasuhiro Yamada(Japan Agency for Marine-Earth Science and Technology (JAMSTEC), R&D Center for Ocean Drilling Science (ODS)), Katsuyoshi Michibayashi(Institute of Geosciences, Shizuoka University), Minoru Ikehara(Center for Advanced Marine Core Research, Kochi University), Yusuke Suganuma(National institute of Polar Research), Chairperson:Yasuhiro Yamada(Japan Agency for Marine-Earth Science and Technology (JAMSTEC), R&D Center for Ocean Drilling Science (ODS)), Chairperson:Fumio Inagaki(Japan Agency for Marine-Earth Science and Technology)

9:45 AM - 10:00 AM

[MIS22-10] The Chicxulub impact crater cores recovered by IODP-ICDP Expedition 364: Status Report

*Naotaka Tomioka1, Kosei E. Yamaguchi2,3, Kazuhisa Goto4, Honami Sato5, Joannna V. Morgan6, Sean P.S. Gulick7, Expedition 364 scientists (1.Kochi Institute for Core Sample Research, JAMSTEC, 2.Department of Chemistry, Toho University, 3.NASA Astrobiology Institute, 4.International Research Institute of Disaster Science, Tohoku University, 5.R&D Center for Submarine Resources, JAMSTEC, 6.Department of Earth Science and Engineering, Imperial College London, 7.Institute for Geophysics, Jackson School of Geosciences, University of Texas at Austin)

Keywords:Chicxulub crater, shock metamorphism, K-Pg boundary, tsunami, PETM

The Chicxulub impact structure in the northern Yucatan Peninsula, Mexico, formed at the Cretaceous-Paleogene boundary (66.0 Ma), was drilled by the joint IODP-ICDP Expedition 364 in April-May 2016. This is the first attempt to obtain materials from the topographic peak ring within the crater previously identified by seismological observations. Major objectives of Exp. 364 are to understand (1) the nature and formation mechanism of peak rings, (2) how rocks are weakened during large impacts, (3) the nature and extent of post-impact hydrothermal circulation, (4) the deep biosphere and habitability of the peak ring, and (5) the recovery of life in a sterile zone.

A continuous core was successfully recovered from the peak ring in the depths between 505.7 and 1334.7 mbsf. After the initial observation on a Mission Specific Platform, the up to 1.5 m-cores were transported to MARUM, University of Bremen, for further analysis at the onshore science party (OSP) held in September-October 2016, where visual core description as well as biostratigraphic (foraminifera and calcareous nannofossil assemblages), geophysical (density, P-wave velocity, paleomagnetism), geochemical (major and minor elements, carbon contents), and petrological analyses (optical microcopy and XRD) of the cores were performed.

The uppermost part of the core (505.7–617.3 mbsf) is post-impact sediments, including PETM, that are mainly composed of carbonate with intercalation of siliciclastic materials that are occasionally rich in organic carbon. Below is a transitional zone that shows a drastic change into impactites (suevite and impact melt rock) with lithologically diverse clasts composed of sedimentary and basement rocks (617.3–747.0 mbsf). We found uplifted, fractured, and shocked granitic basement rocks forming the peak ring below the impactite unit (747.0–1334.7 mbsf). The granitic basement is intruded by mafic and felsic subvolcanic dikes as well as impact melt-breccia dikes. The lithological and physical properties of the Chicxulub cores confirmed the dynamic collapse of an overheightened central uplift of the crater as a favored model for the peak-ring formation [1].

Four Japanese OSP participants have been working on sedimentological, geochemical and mineralogical aspects of the allocated samples to understand various impact and post-impact events: resurge process and tsunami generation, search for projectile component using platinum group elements, elemental and isotopic evolution in the Eocene and Paleocene seawater, shock metamorphism of impactites and basement rocks, hydrothermal alteration of the basement rocks, and the deep biosphere and habitability of the peak ring.

The IODP-ICDP Expedition 364 Science Party is composed of S. Gulick (US), J. V. Morgan (UK), E. Chenot (France), G. Christeson (US), Ph. Claeys (Belgium), C. Cockell (UK), M. J. L. Coolen (Australia), L. Ferrière (Austria), C. Gebhardt (Germany), K. Goto (Japan), H. Jones (US), D. A. Kring (US), J. Lofi (France), C. Lowery (US), C. Mellett (UK), R. Ocampo-Torres (France), A. Rae (UK), C. Rasmussen (US), M. Rebolledo-Vieyra (Mexico), L. Perez-Cruz (Mexico), A. Pickersgill (UK), U. Riller (Germany), M. Poelchau (Germany), H. Sato (Japan), J. Smit (Netherlands), S. Tikoo-Schantz (US), N. Tomioka (Japan), J. Urrutia-Fucugauchi (Mexico), M. Whalen (US), A. Wittmann (US), L. Xiao (China), K. E. Yamaguchi (Japan), and W. Zylberman (France).

References: [1] Morgan et al. (2016) Science, 354, 878–882.