Chicxulub impact crater; mapping suevite, impact melt rock, and the peak ring using full-waveform tomography images

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Author(s): Christeson, Gail Lynn; Morgan, Joanna V.; Gulick, Sean P. S.
Author Affiliation(s): Primary:
University of Texas at Austin, Institute for Geophysics, Austin, TX, United States
Imperial College London, United Kingdom
Volume Title: AGU 2018 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2018; American Geophysical Union 2018 fall meeting, Washington, DC, Dec. 10-14, 2018. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: We present new two-dimensional, full-waveform tomographic velocity images from a grid of seismic data across the Chicxulub impact crater. The full-waveform inversion (FWI) method produces high-resolution velocity models of the upper 1.5-2 km. A prominent feature in the FWI velocity images is a thin (∼100-200 m thick) layer of low-velocity (∼3000-3200 m/s) rocks at a depth just below the K-Pg boundary as previously interpreted on seismic reflection images. Drilling of the peak ring during joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 reveals that the low-velocity layer is suevite (impact melt-bearing breccia). The suevite and underlying 100-m thick impact melt rock layer are referred to as the Upper Peak Ring. The Lower Peak Ring is composed of uplifted granitic target rock that is fractured and shocked, and is identified in the FWI images as a region of reduced seismic velocities. We can use the FWI images to map the suevite within the impact crater, and find that suevite is thinnest on top of the topographically elevated Lower Peak Ring, is of intermediate thickness within the annular trough, and is thickest within the central basin. Mapping of the Lower Peak Ring shows that it is shallow and narrow in the western part of the basin, and deeper and wider in the eastern part of the basin. An additional feature in the FWI images are regions where velocities increase to >5800 m/s associated with a low-frequency reflector. We interpret this as the top of the impact melt sheet on the basis of onshore drilling in the central basin.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 05 Petrology, Igneous and Metamorphic; Atlantic Ocean; Breccia; Chicxulub Crater; Expedition 364; Geomorphology; Gulf of Mexico; Impact breccia; Impact craters; Impact features; Impactites; International Ocean Discovery Program; Metamorphic rocks; North Atlantic; Suevite; Tomography
Coordinates: N212701 N212701 W0895658 W0895658
Record ID: 2019061720
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