Mapping the Chicxulub Impact Stratigraphy and Peak Ring Using Drilling and Seismic Data

摘要

We integrate high-resolution full-waveform velocity models with seismic reflection images to map the peak ring and impactite stratigraphy at the Chicxulub structure. International Ocean Discovery Program/International Continental scientific Drilling Program Site M0077 provides ground truth for our interpretations. The peak ring is narrower (similar to 10 km width) where it is high relief (600-700 m below seafloor) and wider (similar to 15 km width) where it is lower relief (1,000-1,200 m below seafloor). Both target asymmetry and angle of impact could have contributed to observed differences in peak ring morphology. We interpret a layer of lowered velocities as a resurge layer formed from the ocean resurge, seiche, and returning tsunami flowing into the newly formed impact basin. This graded suevite layer has an average thickness of 187 +/- 58 m with only local thickness differences within the annular trough, peak ring, and central basin. These observations suggest that the returning ocean was of substantial height and energetic enough to carry debris across the entire topographic peak ring. We map impact melt rock throughout the crater, with a thick impact melt sheet in the central basin (>500 m), thin intermittent melt rock capping the peak ring, and a similar to 500-m thick layer of melt rock in the annular trough near the peak ring that thins toward the crater rim. We estimate that similar to 70%-75% of the melt rock volume is in the central basin. We image features above and adjacent to the central basin melt sheet that we interpret as upflow zones associated with a long-lasting hydrothermal system.