The ammonite zones of the Bathonian in Bulgaria

A scheme of nine ammonite zones for the Bathonian in Bulgaria is described herein. The stratigraphical distribution of the Bathonian ammonites has been revised through new collecting and re-examination of older collections and fields. It has become evident that the criteria for zonal discrimination applied in NW Europe are relevant for Bulgaria to a limited extent, and we cannot compare directly our successions with those from the NW European areas as done in earlier work. Also, many traits of typically Submediterranean dispersal have been found to take a considerable part of the ammonite associations. Therefore, a composite Submediterranean–NW European zonation seems to be applicable to the Bathonian ammonite successions in Bulgaria. The ammonite zonal scale used in previous Bulgarian accounts has been retained, but several changes have been made to attain a more balanced sequence. This scale can be subject to further confirmation and modification, as not enough biostratigraphically well-constrained specimens have yet become available to characterize the ranges and variability of the zones.