IODP-ICDP Expedition 364: Drilling the peak ring of the Chicxulub impact structure
In 2016 a joint IODP-ICDP expedition drilled the peak ring within the Chicxulub impact structure in Mexico. The aims of Expedition 364 were to investigate: (1) the nature and formational mechanism of peak rings, (2) how rocks are weakened during large impacts, (3) the nature and extent of postimpact hydrothermal circulation, (4) the deep biosphere and habitability of the peak ring, and (5) the recovery of life in a potentially, sterile zone. Other key targets included: sampling the transition through a rare midlatitude section that might include Eocene and Paleocene hyperthermals and/or the Paleocene/Eocene Thermal Maximum (PETM), and any observations from the core that may help us constrain the volume of dust and climatically active gases released into the stratosphere by this impact.
Core was recovered between 505.70 and 1334.73 mbsf, and included: ~110 m of Eocene and Paleocene sedimentary rocks, ~130 m of suevite (impact breccia) and clast-poor impact melt rock, and ~590 m of uplifted, highly-fractured and shocked granitic basement rocks. There was excellent core recovery, and the recovered core and wireline logs are of excellent quality. Peak-ring formation was a topic of a recently published article, and progress has been made on several of the other goals. Currently, I am using high-resolution velocity models obtained from full-waveform inversions to map the thickness of the suevite layer and top of felsic basement across the peak ring, and track the suevite away from the borehole into the surrounding annular trough and central basin.