VOLUME 53 (3)/December 2024

The most used rock materials that served to build the modern appearance of Sofia’s central streets and buildings are presented. Different local genetic types of rocks were utilized for the construction of modern Sofia: igneous rocks (monzonites, gabbros, rhyolites); sedimentary rocks (varieties of limestone and sandstones); and metamorphics (mainly marbles). A small part of rock materials was imported, mainly for the interior design of the buildings, for instance in Sofia University “St. Kliment Ohridski”, St. Alexander Nevsky Cathedral, and others. The most used rock material for buildings and streets were the monzonites from the Vitosha Mountain, and this is the reason why Sofia City is noted as “the monzonite capital” of Bulgaria. The emblematic buildings, streets and squares in the city centre, with their rock building material, characteristics, and historical significance are briefly described.

The El Pintado 1 section of the Ossa-Morena Zone (Valle syncline, SW Spain) includes a rather continuous stratigraphic succession ranging from the Upper Ordovician to the Devonian, including remarkably fossiliferous black graptolitic shales that begin their sedimentation in the basal Silurian Akidograptus ascensus graptolite Biozone. The investigation for the location of the Ordovician–Silurian boundary in previous beds has produced negative results, due to the existence of a probable basal gap equivalent to the lower part of the aforementioned biozone, and the absence of stratigraphically relevant fossils, such as graptolites or conodonts, that could provide a high-resolution biostratigraphy to the Hirnantian succession. Nonetheless, some interesting records of rare shelly fossils in the Valle Shale (Hirnantian) are presented, and the Rhuddanian graptolite biozonation in the lower 38 m of the Lower Graptolite Shale (Rhuddanian to Ludfordian) is discussed.

The Devonian sediments from the Moesian Terrane (Moesian Platform, northern Bulgaria) are known only from oil and gas prospecting wells. Middle and Upper Devonian deposits are interpreted as formed in great variety of depositional settings. Thus, the Eifelian carbonates were regarded as inner- and mid ramp deposits developed in a shallowing-upward sequence. The shallowing tendency continued during the Givetian and Frasnian, when arid tidal-flat and lagoon settings predominated. At the beginning of the Famennian, a climate change occurred when the Moesian Terrane was removed from the Subtropical Arid to the Warm Temperate Climatic Zone. Then, carbonate deposition took place in various shallow- to deepermarine environments.

The Makarovian Regional Substage (Famennian Stage) stratigraphic interval is defined more accurately in the Kuk-Karauk stratotype section (Sikasya River, west slope of the Southern Urals) by conodonts. It is equal to the Pa. minuta minuta, Pa. crepida, Pa. rhomboidea, Pa. marginifera marginifera conodont zones. The absence of intervals equal to the Pa. termini, Pa. glabra prima, Pa. glabra pectinata and Pa. gracilis gracilis zones is testifies to a hiatus. The Pa. crepida and Pa. rhomboidea zones are revealed in the studied section for the first time. Conodont complexes are characterized by rich taxonomic and quantitative diversity (six genera and 48 species). Species of the genus Palmatolepis (up to 92%), which are representatives of deepwater palmatolepid biofacies, predominate.

The Sredogriv metamorphics are located in NW Bulgaria and referred to the Balkan Terrane. They represent an alternation of different parametamorphites and, to a lesser extent, polymict metaclastic rocks, phyllites and calcareous schists. Various in size allochthonous bodies from metamorphosed magmatites have been tectonically included among them. Recent studies on the Sredogriv metamorphics indicate their formation in a marginal basin of probable Silurian–Devonian age affected by subsequent Carboniferous tectonic processes and greenschist metamorphism.