Chitinozoan Biostratigraphy of the Early Caradocian Locke Impact Structure, Jämtland, Sweden

The chitinozoan biostratigraphy in seven outcrops and four drillings in connection with the Locke impact structure has been investigated. The impact event took place in early Caradoc (i.e., ~460.4 Ma ago) and in beds corresponding to the lower part of the Lagenochitina dalbyensis Zone (upper Dalby Limestone). The contact between the impact-related rocks and the secular postimpact sediments can be traced all over the impact structure, and up to a distance of 50 km away from the presumed crater center. The youngest postimpact sediments in the Locke impact structure correspond to the lower Örå Shale (Belonechitina hirsuta Zone).