Origin of the Early-Middle Jurassic stratigraphic gaps in the Central Balkanids

Numerous stratigraphic gaps are known from the Bulgarian Lower and Middle Jurassic sections. The more considerable of them a priori have been accepted as a result of regressions, emersions, erosion and new transgressions.
   The most attractive among the Early-Middle Jurassic gaps in this country is the pre-Callovian stratigraphic gap which is very well developed in the Central Balkanids. We made a palaeoecologic (Sapunov) and microfacial (Belivanova) study of the sediments just below and above the gap in limited localities where the gap is a diastem and usually is marked by hardgrounds. Beside this, we made a similar research in continuous Bathonian-Callovian sections in the West Balkan Range. The aim of this research was the comparison between the depositional environments of the continuous Bathonian-Callovian sediments and the Bathonian and Callovian from the cover and the basement of the pre-Callovian diastem in the Central Balkanids.