Chicxulub impact crater: Shock metamorphism, structure, and petrology of impact formations

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As part of the ICDP "Chicxulub Scientific Drilling Project" we propose to study the 1500 m deep CSDP drill core located inside the 180-200 km Chicxulub multiring impact structure, with regard to (1) shock metamorphism and (2) post-shock deformations induced by the highly dynamic collapse of the transient crater cavity. From the intensity and distribution of shock effects analyzed in all types of impact breccias and in the crater basement the shock pressure attenuation in the target rocks and estimates of the dimension of the transient cavity will be obtained. In the displaced basement rocks deformations which are induced by the dynamic crater collapse (cataclasites, fault gouges and breccias, and pseudotachylites), and post-impact thermal effects will be analyzed by fabric, microstructural, geochemical, and fluid inclusion analyses. We expect to deduce dominant deformation mechanisms of individual rock constituents and the role of fluids during crater collapse in order to verify (falsify) current models for the low strength material behavior under dynamic conditions of crater collapse (Bingham fluid and acoustic fluidization models) as opposed to normal tectonic deformation processes. We also intend to assess the kinematic history of the transient cavity collapse, and the process leading to the shallow, multiringed impact basin on very short time scales. The proposed research will contribute to establish a quantitave empirical model of the formation of complex, multiring impact basins on Earth which will have also important implications for the evolution of other planetary surfaces and crusts.