Permian in North Bulgaria. II : Formal lithostratigraphy related to the Upper Permian

The following nine official lithostratigraphic units are subdivided and described within the frames of an Upper Permian Lower Danube Group in accord with the requirements of the Bulgarian Stratigraphic Code: Mirovo Formation, Vetrino Formation (with Žitnica and Hrabrovo Menber), Târgoviste Formation (with Trastikovo and Bezvodica Member), Totleben Formation and Sokolare Formation. The Mirovo Formation consists of greyish-black shales, a small amount of siltstones, maris dolomites and anhydrites. The Vetrino Formation is built up of alternating argillaceous chemogeneous rocks with che mogeneous (mainly evaporitic) sediments (halite, anhydrite, dolomite), a small amount of aleuropsamitic rocks and limestones. The Hrabrovo Member (mainly chemogeneous rocks and a lot of halite-argillaceous breccia) interfingers laterally with the Žitnica Member (predominating terrigenous-clayey sediments, little evaporite). The Târgovište Formation consists of massive and poorly sorted red aleuropelitic sediments and hyposandstones and bears some anhydrite and carbonate concretions. The growth of the formation in layered andhydrites and dolomites is subdivided as Bezvodica Member, while the sections bearing some chemogeneous admixtures - as Trâstik Member. The Totleben Formation is an alternation of thin-bedded, well-sorted shales, siltstones and sandstones in various colours - whitish, reddish-brown, grey-greenish and other hues - changing with the beds. The Sokolare Formation is distinguished for coarser but better sorted rocks: sandstones, gravelites, non-saturated conglomerates with subsidiary interbeds of hyporocks. The formations of Mirovo, Vetrino, Trgovište and Totleben are in superpositional relationships without being ubiquitously spread. The Trâstikovo and Bezvodica Members interfinger laterally, and at certain places the Bezvodica Member lies on a higher level within the Târgovište Formation. At present the Mirovo and Vetrino Formations are known within the range of the Provadia Syncline. The Totleben Formation has been outcropped east of the Vit River, and the Sokolare Formation - ubiquitously in the eastern part of Dobrudža. The most widely spread - from the town of Vidin to the Black Sea coast - is the Târgovište Formation. The lithostratigraphic scheme of Permian is important for the correlations and interpretations of the entire Moesian area (incl. its Romanian part) and also for the oil-gas prospects of Paleozoic thanks to the screening capacity of part of th