The Internal Stratigraphy of K/T Boundary Sediments and Implications for their Provenance

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This study will examine the stratigraphy of Cretaceous/Tertiary boundary sediments deposited in the proto- Caribbean region to determine their provenance, the way in which they were transported, and how local conditions may have influenced their deposition. In particular, we will determine the size distribution of impact melt spherules, both as a function of stratigraphic height and with distance from their source; determine the compositions of impact melt spherule glasses, whether they vary with stratigraphic height or with distance from their source, and infer their provenance based on their compositions; determine the distribution of shocked mineral phases (such as quartz, feldspar, and spinel) with stratigraphic height and infer their provenance; use this information to determine criteria which can be used to assess whether a deposit of boundary sediments is undisturbed or has been reworked; and determine the overall thicknesses of undisturbed boundary sediments. These observations of boundary sediments will be coupled with theoretical calculations of ejecta transport. The combined studies should identify the approximate location of the source crater and the lithologies of the target material, both of which should determine whether the Chicxulub structure, which we have proposed to be the location of a terminal Cretaceous impact, is a viable candidate. The study should also have wide application to the deposition of ejecta from large (100 km) craters, a subject which is poorly understood at the present time.