VOLUME 45 (-)/December 2016

Seven carbonate microfacies types (MFT 1–7) have been distinguished and described in the Givetian dolomite formation from the Totleben-2 well (Moesian Platform, central North Bulgaria). They have been grouped in three microfacies associations: 1) shallow subtidal microfacies with open circulation (MFT 1, coral-stromatoporoid floatstone/rudstone; and MFT 2, brachiopod floatstone/rudstone); 2) protected shallow subtidal microfacies (MFT 3, intraclastic-ooidal packstone/grainstone; MFT 4, palaeosiphonoclad wackestone/packstone; and MFT 5, bioclastic-peloidal packstone/grainstone); 3) intertidal-supratidal microfacies (MFT 6, fenestral microbial bindstone; and MFT 7, mudstone to packstone with Palaeomicrocodium). These microfacies have been interpreted as formed in dominantly shallow subtidal lagoon setting with open to moderate circulation and locally developed intertidal/supratidal environments. Most microfacies are comparable with Wilson’s (1975) Standard Microfacies Types (SMFT) and/or with Givetian microfacies described from the eastern part of the Moesian Platform, as well as with other shallow-marine Devonian successions from Europe.

New data on the heteromorph ammonite species Diplomoceras cylindraceum (Defrance, 1816) have been obtained from three localities of the Western Fore-Balkan (West Bulgaria). A retrospection of the earlier Bulgarian records is also presented. This characteristic species is relatively common in Bulgaria and, based on both previously and the newly collected data, it is confined to the Maastrichtian. Owing to the difficulty in collecting enough specimens, the amount of variation in ribbing and whorl-section shape, which have been used by other authors for determination of more species within Diplomoceras, is difficult to judge. Nevertheless, the Bulgarian material reveals that rib density varies in broad limits and the rib index does not show a sufficient degree of variance to warrant the distinction of more than one species. Therefore, it is doubtful that all specific names that have been proposed in the literature for rib differences represent other species than Diplomoceras cylindraceum.

Geochemical studies of seasonally collected mine, stream and drinking waters, bottom sediments (mine and stream) and soil samples from all mining sections were carried out in order to assess the rates of pollution in the immediate proximity to underground mining facilities and related waste rock dumps. The determined concentrations of studied elements in water (As, Pb, Cu, Zn and Sb) show spatial distribution corresponding to ore mineralisation in different sections. Arsenic concentrations show gradual decrease in west-east direction, whereas Pb concentrations peak in the central and eastern sections. Arsenic and, to a lesser extent, Pb proved to be major pollutants in mine and surface waters, as well as in bottom sediments and soils. Detailed geochemical study of soils revealed strong spatial relation with host rocks and ore mineralogy. Comparisons with state guidelines for harmful elements revealed that alluvial and meadow soils in close proximity to waste dumps contain As, Pb, Cu, Zn and Cd above maximum permissible levels. It was also found that, compared to other Bulgarian and world alluvial (fluvisol) soils and the upper continental crust, the soils in Chiprovtsi mining district are enriched in Te, Re, W, Pd, Au, Ag, Mo, Ti, Mn, Co, Se, Sb, Bi and Cs. Since the processes of weathering and oxidation of mine waste remaining in the area continue naturally, the pollution with As and Pb will presumably carry on with decreasing effect.

No abstract is available for this article.