GEOCHEMICAL AND PETROGRAPHIC CHARACTERIZATION OF THE SUEVITE SEQUENCE WITHIN THE IODP-ICDP EXP. 364 CORE OF THE CHICXULUB PEAK RING

Introduction: In May 2016, the IODP-ICDP
Expedition 364 drilled the peak ring of the buried
Chicxulub impact structure in Mexico and obtained a
104 m thick continuous sequence of suevite between
core 40.1 and 87.2 (617.33 – 721.62 mbsf, defined as
unit 2A-2C by [1]). This succession provides vital
information on the different target lithologies affected
by the impact and gives a snapshot into the sequence of
dynamic processes that occurred in the peak ring zone
in the first minutes to hours after the impact [2].
Suevite is defined as an impact melt-bearing
polymict breccia with a particulate matrix [3]. However,
the emplacement mechanisms of suevite are still under
debate, as these are highly dependent on the
characteristics of the target stratigraphy and the
presence or absence of (sea)water. For Chicxulub, the
target was a shallow marine environment with a
carbonate-evaporite platform on top of a crystalline and
metamorphic basement [4]. Over the last decades,
several formational scenarios have been suggested for
the suevite in the Chicxulub crater, varying from ground
surging-density currents [5], fallback due to the collapse
of the ejecta plume [5], tsunami resurge [6] and
phreatomagmatic (molten fuel coolant) interaction [7].
The IODP-ICDP Exp. 364 core sheds a new light on
the Chicxulub suevite conundrum, because it shows a
continuous succession with intact contacts with the
lower lying impact melt rock sequence (unit 3A-B) and
the transitional unit (unit 1G) above. Here, we present a
detailed petrographic, mineralogic, and geochemical
dataset, both bulk and clast-specific, covering the entire
suevite sequence to characterize and interpret this unit.