Physical properties of the Yaxcopoil‐1 deep drill core, Chicxulub impact structure, Mexico

Abstract

Abstract-The Chicxulub structure in Mexico, one of the largest impact structures on Earth, was formed 65 Ma by a hypervelocity impact that led to the large mass extinction at the K-Pg boundary. The Chicxulub impact structure is well preserved, but is buried beneath a sequence of carbonate sediments and, thus, requires drilling to obtain subsurface information. show that the various lithologies, including the impactite units and the K-Pg boundary layer, can be characterized by their physical properties, which depend on either changes in fabric or on mineralogical variations. The magnetic properties show mostly dia-or paramagnetic behavior, with the exception of the impactite units that indicate the presence of ferromagnetic, probably hydrothermally deposited magnetite and pyrrhotite. The magnetic fraction contributes mainly to enhanced magnetization in the impactite lithologies and, in this way, to the observed magnetic anomalies. The shape and orientation of the magnetic grains are varied and reflect inhomogeneous fabric development and the influence of impact-related redeposition and hydrothermal activity. The Chicxulub impact occurred at the time of the reverse polarity geomagnetic chron 29R, and this finding is consistent with the age of the K-Pg boundary.

Shock experiments in range of 10–45 GPa with small multidomain magnetite in porous targets

“…2007; Gattacceca et al. 2010) or/and to postimpact hydrothermal mineralization (Elbra and Pesonen 2011).…”

“…Such newly grown magnetite can form either from the melt (Deutsch et al. 1992) or under the influence of hydrothermal fluids circulating in impactite layers or within the fractured target rocks (Elbra and Pesonen 2011). Magnetite is also reported to be present in some Martian meteorites (Rochette et al.…”

“…net/EarthImpactDatabase/index.html) reveals over 180 confirmed impact structures of which more than 30% are located in crystalline target rocks, and another 33% in a mixed sedimentary-crystalline target. The terrestrial impact structures (Pilkington and Grieve 1992;Plado et al 1996;Pesonen et al 1999;Pesonen 2011; and references therein) as well as those on Moon (Halekas et al 2003) and Mars (Hood et al 2003;Kletetschka et al 2004b;Shahnas and Arkani-Hamed 2007) are often associated with magnetic anomalies related either to shock or ⁄ and postimpact heating (e.g., Hargraves and Perkins 1969;Wasilewski 1973;Pohl et al 1975;Cisowski et al 1976;Fuller 1978, 1982;Pesonen et al 1997;Kontny et al 2007;Gattacceca et al 2010) or ⁄ and to postimpact hydrothermal mineralization (Elbra and Pesonen 2011).…”

“…Magnetite is also a common magnetic mineral in impactites, either derived directly from the target rocks or appearing as a newly impact-generated oxide. Such newly grown magnetite can form either from the melt (Deutsch et al 1992) or under the influence of hydrothermal fluids circulating in impactite layers or within the fractured target rocks (Elbra and Pesonen 2011). Magnetite is also reported to be present in some Martian meteorites (Rochette et al 2005) and, thus, most likely exists in the Martian crust.…”

Three-dimensional gravity modeling of Chicxulub Crater structure, constrained with marine seismic data and land boreholes

“…Data on physical properties have been reported from analyses on samples from borehole cores (e.g., Sharpton et al, 1996;Urrutia-Fucugauchi et al, 1996;Vermeesch and Morgan, 2004;Mayr et al, 2008;Elbra and Pesonen, 2011). Data are however limited to the upper formations of the carbonate sequences and breccias, which have been sampled in the boreholes.…”