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This study presents a new classification of a ∼100-m-thick crater suevite sequence in the recent International Ocean Discovery Program (IODP)-International Continental Scientific Drilling Program (ICDP) Expedition 364 Hole M0077A drill core to better understand the formation of suevite on top of the Chicxulub peak ring. We provide an extensive data set for this succession that consists of whole-rock major and trace element compositional data (n = 212) and petrographic data supported by digital image analysis. The suevite sequence is subdivided into three units that are distinct in their petrography, geochemistry, and sedimentology, from base to top: the ∼5.6-m-thick non-graded suevite unit, the ∼89-m-thick graded suevite unit, and the ∼3.5-m-thick bedded suevite unit. All of these suevite units have isolated Cretaceous planktic foraminifera within their clastic groundmass, which suggests that marine processes were responsible for the deposition of the entire M0077A suevite sequence. The most likely scenario describes that the first ocean water that reached the northern peak ring region entered through a N-NE gap in the Chicxulub outer rim. We estimate that this ocean water arrived at Site M0077 within 30 minutes after the impact and was relatively poor in rock debris. This water caused intense quench fragmentation when it interacted with the underlying hot impact melt rock, and this resulted in the emplacement of the ∼5.6-m-thick hyaloclastite-like, non-graded suevite unit. In the following hours, the impact structure was flooded by an ocean resurge rich in rock debris, which caused the phreatomagmatic processes to stop and the ∼89-m-thick graded suevite unit to be deposited. We interpret that after the energy of the resurge slowly dissipated, oscillating seiche waves took over the sedimentary regime and formed the ∼3.5-m-thick bedded suevite unit. The final stages of the formation of the impactite sequence (estimated to be <20 years after impact) were dominated by resuspension and slow atmospheric settling, including the final deposition of Chicxulub impactor debris. Cumulatively, the Site M0077 suevite sequence from the Chicxulub impact site preserved a high-resolution record that provides an unprecedented window for unravelling the dynamics and timing of proximal marine cratering processes in the direct aftermath of a large impact event. 

Abstract Core from Hole M0077 from IODP/ICDP Expedition 364 provides unprecedented evidence for the physical processes in effect during the interaction of impact melt with rock-debris-laden seawater, following a large meteorite impact into waters of the Yucatán shelf. Evidence for this interaction is based on petrographic, microstructural and chemical examination of the 46.37-m-thick impact melt rock sequence, which overlies shocked granitoid target rock of the peak ring of the Chicxulub impact structure. The melt rock sequence consists of two visually distinct phases, one is black and the other is green in colour. The black phase is aphanitic and trachyandesitic in composition and similar to melt rock from other sites within the impact structure. The green phase consists chiefly of clay minerals and sparitic calcite, which likely formed from a solidified water–rock debris mixture under hydrothermal conditions. We suggest that the layering and internal structure of the melt rock sequence resulted from a single process, i.e., violent contact of initially superheated silicate impact melt with the ocean resurge-induced water–rock mixture overriding the impact melt. Differences in density, temperature, viscosity, and velocity of this mixture and impact melt triggered Kelvin–Helmholtz and Rayleigh–Taylor instabilities at their phase boundary. As a consequence, shearing at the boundary perturbed and, thus, mingled both immiscible phases, and was accompanied by phreatomagmatic processes. These processes led to the brecciation at the top of the impact melt rock sequence. Quenching of this breccia by the seawater prevented reworking of the solidified breccia layers upon subsequent deposition of suevite. Solid-state deformation, notably in the uppermost brecciated impact melt rock layers, attests to long-term gravitational settling of the peak ring. 

Chicxulub sorted suevite records clues to its formation and emplacement that challenge interpretations and models. 

Determining the nature and age of the 200-km-wide Chicxulub impact target rock is an essential step in advancing our understanding of the Maya Block basement. Few age constraints exist for the northern Maya Block crust, specifically the basement underlying the 66 Ma, 200 km-wide Chicxulub impact structure. The International Ocean Discovery Program-International Continental Scientific Drilling Program Expedition 364 core recovered a continuous section of basement rocks from the Chicxulub target rocks, which provides a unique opportunity to illuminate the pre-impact tectonic evolution of a terrane key to the development of the Gulf of Mexico. Sparse published ages for the Maya Block point to Mesoproterozoic, Ediacaran, Ordovician to Devonian crust are consistent with plate reconstruction models. In contrast, granitic basement recovered from the Chicxulub peak ring during Expedition 364 yielded new zircon U-Pb laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) concordant dates clustering around 334 ± 2.3 Ma. Zircon rare earth element (REE) chemistry is consistent with the granitoids having formed in a continental arc setting. Inherited zircon grains fall into three groups: 400−435 Ma, 500−635 Ma, and 940−1400 Ma, which are consistent with the incorporation of Peri-Gondwanan, Pan-African, and Grenvillian crust, respectively. Carboniferous U-Pb ages, trace element compositions, and inherited zircon grains indicate a pre-collisional continental volcanic arc located along the Maya Block’s northern margin before NW Gondwana collided with Laurentia. The existence of a continental arc along NW Gondwana suggests southward-directed subduction of Rheic oceanic crust beneath the Maya Block and is similar to evidence for a continental arc along the northern margin of Gondwana that is documented in the Suwannee terrane, Florida, USA, and Coahuila Block of NE México. 

We report on the effect of the end-Cretaceous impact event on the present-day deep microbial biosphere at the impact site. IODP-ICDP Expedition 364 drilled into the peak ring of the Chicxulub crater, México, allowing us to investigate the microbial communities within this structure. Increased cell biomass was found in the impact suevite, which was deposited within the first few hours of the Cenozoic, demonstrating that the impact produced a new lithological horizon that caused a long-term improvement in deep subsurface colonization potential. In the biologically impoverished granitic rocks, we observed increased cell abundances at impact-induced geological interfaces, that can be attributed to the nutritionally diverse substrates and/or elevated fluid flow. 16S rRNA gene amplicon sequencing revealed taxonomically distinct microbial communities in each crater lithology. These observations show that the impact caused geological deformation that continues to shape the deep subsurface biosphere at Chicxulub in the present day. 

Poster presentation of shock metamorphic features of accessory minerals in drill core samples of the Lower Peak Ring section of the Chicxulub impact crater. 

Oral presentation of petrographic and zirconologic data of drill core samples of suevitic and impact melt rocks from the peak ring of the Chicxulub impact crater.