A fossil proof for the origin of the Hirnantian glaciomarine record in Bulgaria: A preliminary result

The Sirman Formation in the Svoge Unit is built of Hirnantian diamictites, a product of the Gondwana glaciation at the end of the Ordovician. One subangular lonestone of light gray sandstone of size of about 1 cm was found in the lower part of the formation. This pebble, interpreted as a glacial dropstone, contain a relatively well-preserved external negative mould of a trilobite pygidium, which has tentatively been identified as Dreyfussina cf. libyca in absence of cephalic characters. The nominal species was described from the Melaz Shuqran Formation of Libya (Al Qarqaf Arch). The present record supports an African origin for pebbles transported by floating ice to the sediments of the Svoge Unit, consistent with provenance data – the Trans-Saharan Belt, derived from the detrital zircons recorded on the same Hirnantian diamictites in Bulgaria.