Proximal Carbonate Ejecta From the Cretaceous-Tertiary Chicxulub Impact Crater: 87Sr/86Sr Chronology, Ballistic Sedimentation, and Diagenetic Alteration

University Of Illinois At Urbana-Champaign, Urbana IL

Investigators

Abstract

9909560 Fouke A large-body impact at the Cretaceous-Tertiary (KT) boundary targeted 3 km of carbonate platform covering crystalline basement on the Yucatan peninsula. This study seeks to reconstruct the sediment transport dynamics and geochemistry of the KT impact by analyzing ballistically ejected carbonate sediments deposited close to the Chicxulub crater. The age, source, transport mechanisms, and post-depositional alteration of these deposits will be reconstructed from a well-exposed platform top section at Albion Island, Belize. Accretionary lapilli interpreted to be of impact origin will also be analyzed from the platform margin El Guay section in Mexico, The genesis of these impact-derived sediments will be determined using cathodolumineseence (CL) petrography, elemental and isotopic geochemistry (bulk rock and microsamples), and quantitative water-rock interaction modeling. Preliminary analyses have identified several CL-distinct crystalline features in the lapilli and breccia blocks that will provide important new constraints on vapor cloud sedimentary mechanisms and geochemistry. Tests will be conducted to determine whether symmetrical trends in global seawater 87sr/86 Sr standard curve (0.7077 to 0.7079) through the KT boundary can be used to determine: (1) the depositional age of original sedimentary components (breccia blocks, lapilli, skeletal material, marine cements), and (2) syndepositional or early post-depositional events of impact glass