ASTEROID IMPACTS - THE CHESAPEAKE BAY CRATER CORE (Eyreville) - the syn-impact post-impact transition.

This project is based on sedimentological, petrological and clay mineralogical analyses of core samples from syn-impact post-impact transition of the recent Eyreville core of the Chesapeake Bay impact crater. We are aiming at the following: a. In the Chic xulub and Mjølnir structures, altered glasses are found as clay minerals (often smectites). The alteration of glass is a fast process in nature. Clay mineralogical analyses may be one way of detecting if any impact glass had been formed in the crater. The clay mineralogical results may also be used to correlate crater deposits and tektites, e.g. from the possibly related North American strewn field. b. Hydrothermal processes may have been active in the post-impact history of the crater. During hydrotherma l activity clay mineral formation and mineral transformation takes place. The clay mineralogical studies may shed new light on such alteration in the Chesapeake Bay. Normal circulating groundwater may produce a distinct mineralogical signature. c. It is p ossible that the timing of the possible glass to clay minerals alteration and syn-sedimentary glauconite formation can help in dating the impact, in the case glass phases are missing. d. In some cases clay minerals can be used to recognize specific sourc e rocks/areas, this may be possible here. Basement rocks, older sedimentary units and weathering horizons could all carry special clay mineralogical fingerprints. Consequently the clay mineralogical composition may give additional information on the mecha nisms of crater filling and paleoclimatic conditions in the surrounding region. e. Clay minerals are transformed and altered during increasing burial. They could in this case give information on the burial history of the Chesapeake Bay crater. f. The res ults will be used in comparative analyses with the marine impacts of Chicxulub (Gulf of Mexico), Mjølnir (Barents Sea) and Gardnos (Hallingdal).