The Silurian and the Devonian in the Svoge Unit, Western Bulgaria – a brief overview

Five stops, containing Silurian–Devonian strata of the Svoge Unit (Western Bulgaria) are described. At Stop 1 near the village of Tsarichina, Upper Devonian flysch (Katina Formation) can be observed, which ends the Paleozoic marine sedimentation in the area. The other two Devonian formations are observable at stop 2 near the village of Vlado Trichkov. These are the black shales of the Ogradishte Formation and the light shales of the Romcha Formation. At the village of Tseretsel (stop 3), all Silurian units are observed: the bedded cherts (lydites) of the Saltar Formation, the graptolite-bearing black shales of the Mala Reka Formation, and the grey to gray-green laminated shales of the Yabukov Dol Formation. The boundaries of the Silurian System, based on graptolites, were established at the next two stops, respectively at stop 4 the Silurian/ Devonian boundary and at stop 5 the Ordovician/Silurian boundary.