Silurian Graptolite Sites in Bulgaria: Geological Settings and Geoconservation Value

Seven exceptional paleontological graptolite sites of Silurian age located in the Srednogorie Zone (the Svoge Unit and the Lyubash-Golo Bardo Unit) and the Moravo-Rhodope Zone (the Morava Unit) of the Alpine Orogenic Belt in Western Bulgaria are described. The graptolitic deposits include predominantly thin-bedded shales referred to 4 formal lithostratigraphic units in the Svoge Unit, and one informal lithostratigraphic unit in both the Lyubash-Golo Bardo and Morava units. This article provides a historical review of the foundation and description of the graptolite sites thus providing a better understanding of their historical value for stratigraphy and the geological evolution of this area during the Silurian. An analysis of their geotourism potential and geoconservation value, according to the new indicative criteria highlighting the specific characteristics of fossil sites, is also given.