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Figure 5. (A) The Chicxulub peak ring in 83-mm-diameter core is composed of granitic rocks, crosscut with cataclastic and hydrothermal veins, that
have also been shock-metamorphosed, as illustrated with planar deformation features with ~5 micron spacing in quartz (inset, with field of view 245
microns wide). Photomicrograph of quartz by expedition scientist Ludovic Ferrière. (B) Granitic basement (pink) was uplifted and then collapsed out-
ward over the pre-impact crust (yellow). The portion of the peak ring sampled in the core also contains shock-metamorphosed (blue) and melted (red)
components, which are consistent with a numerical model of dynamic collapse of a central uplift during the crater-forming event (Morgan et al., 2016).
While the numerical model treats the basement as a uniform unit of granite, which is the rock type that dominates the new IODP-ICDP core, the base-
ment also contains metaquartzite, mica schist, granitic gneiss, gneiss, amphibolite, dolerite dikes, dacite, felsite, and granodiorite (Kring, 2005;
Gulick et al., 2017).

Confidence in the dynamic collapse CONCLUSIONS (Mexico); M. Whalen (U.S.); A. Wittmann (U.S.);
model, finally tested with core samples, L. Xiao (China); K.E. Yamaguchi (Japan); and
has grown substantially. New IODP-ICDP borehole data indicate W. Zylberman (France). The European
that the peak-ring morphology of the Consortium for Ocean Research Drilling
The Chicxulub peak ring had an eleva- Chicxulub crater was produced by the (ECORD) implemented Expedition 364 with
tion below that of the crater rim. As dynamic collapse of an uplifted central contributions and logistical support from the
inferred from analogy with the peak. Additional exciting expedition Yucatán state government and Universidad
Schrödinger basin peak ring, and inferred results are forthcoming. The impact gener- Nacional Autónoma de México (UNAM). We
from seismic reflection data, the peak ring ated an environmental calamity that extin- thank Wright Horton and Christian Koeberl for
had a topographically complex surface. guished life. It also induced a vast sub- helpful reviews.
There were highs subject to erosion and surface hydrothermal system that altered a
lows suitable for near-continuous sedimen- portion of the Maya Block and serves as a REFERENCES CITED
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