Magnetic fabrics and properties of impactites and basement beneath the peak ring of Chicxulub Crater; IODP-ICDP Expedition 364

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http://abstractsearch.agu.org/meetings/2018/FM/PP51D-1165.html
Author(s): Urrutia-Fucugauchi, Jaime; Perez-Cruz, Ligia L.; Tikoo, Sonia; Riller, Ulrich P.; Rebolledo-Vieyra, Mario; Morgan, Joanna V.; Gulick, Sean P. S.
Author Affiliation(s): Primary:
Universidad Nacional Autonoma de Mexico, Mexico City, Mexico
Other:
Rutgers University, United States
Geologisch-Palaeontologische Institut, Germany
Center for Research and Advanced Studies of the National Polytechnic Institute, Mexico
Imperial College London, United Kingdom
University of Texas at Austin, United States
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: IODP-ICDP Expedition 364 drilled into the peak ring of Chicxulub crater and showed that felsic basement rocks underlie impactites at shallow depth. Geophysical surveys show that the peak ring is marked by low seismic velocity and rock density. Recovered drill core offers the opportunity to study the physical rock properties and mechanisms of peak ring formation. The borehole was continuously cored from 505.7 m to 1334.7 m depth below sea floor. Here, we present results of a rock magnetic study of post-impact sediments, Upper Peak Ring impactites and the basement rocks, including felsic dikes, of the Lower Peak Ring. The Upper Peak Ring section shows variable and rather high susceptibilities and remanent magnetization intensities, with a thick melt rock unit at the base characterized by the highest magnitudes in both. Hysteresis loops show saturation at low fields, with fine-grained magnetic particles of pseudo-single domain states. The Lower Peak Ring basement rocks show variable, but lower susceptibilities and magnetization intensities, with higher values in the pre-impact and impact-related dikes, particularly towards the base of the section. The susceptibility vs. temperature curves indicate Curie temperatures around 500-580 degrees C, corresponding to titanomagnetites and magnetite as magnetic carrier minerals. In some cases, there is indication of maghematization and titanohematites. The variation vs. temperature curve shows irreversible behavior, suggesting rocks were not heated to high temperature after magnetite formation. Magnetic fabrics are examined at centimeter-scale by measuring the anisotropy of magnetic susceptibility (AMS). Results show that basement rocks are characterized by higher anisotropy degree than observed in breccias. AMS ellipsoid shapes in breccias show oblate and prolate fabrics; whereas the basal melt unit is marked by prolate fabrics. In contrast, Lower Peak Ring basement shows dominantly oblate fabrics, possibly associated with planar geometry of fabrics during cratering and fracturing of quartz, feldspars and biotites. Deformation in granitoid basement rock is shown at various scales, with pre-impact magmatic and impact-induced structures, and further analyses are needed to separate the signals in the AMS data.
Year of Publication: 2018
Research Program: IODP2 International Ocean Discovery Program
Key Words: 23 Surficial Geology, Geomorphology; Atlantic Ocean; Basement; Chicxulub Crater; Expedition 364; Fabric; Geomorphology; Gulf of Mexico; Impact craters; Impact features; International Ocean Discovery Program; Landform evolution; Magnetic properties; North Atlantic
Coordinates: N212701 N212701 W0895658 W0895658
Record ID: 2019061716
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