Biostratigraphy of Lochkovian Chitinozoans from North Bulgaria

A part of the Silurian–Lower Devonian terrigenous argillaceous succession from the subsurface of the Moesian Platform (North Bulgaria) is dated by chitinozoans as Lochkovian (Early Devonian). Four successive chitinozoan zones are defined and described. From the base to the top they are: the Angochitina chlupaci – Ancyrochitina tomentosa Interval Biozone, the Ancyrochitina tomentosa – Urochitina simplex Interval Biozone, the Urochitina simplex Total Range Biozone and the Urochitina simplex – Cingulochitina plusquelleci Interval Biozone. The wide geographical distribution of the distinctive Lochkovian chitinozoan taxa A. chlupaci Paris and Laufeld, 1981, A. tomentosa Taugourdeau and de Jekhowsky, 1960, Fungochitina pistilliformis lata Taugourdeau and de Jekhowsky, 1960, C. plusquelleci Paris, 1981 and U. simplex Taugourdeau and de Jekhowsky, 1960, have made it possible to correlate the Bulgarian zones with zones and subzones proposed previously in the North Gondwana Region. There is closer similarity with the Lochkovian chitinozoan assemblages from North Africa than with those from western and central Europe.