3D lithostratigraphic model of the Paleogene of the onshore part of the Moesian Platform (Northeast Bulgaria)

Abstract

The Paleogene sedimentary rocks in the north-easternmost part of the territory of Bulgaria have been penetrated by numerous boreholes. In terms of regional tectonic zonation, the study area is a part of the onshore sector of the Moesian Platform, which partly includes the South Dobrogea Unit and the easternmost part of the North Bulgarian Dome with its eastern slope. The lithostratigraphy of the Paleogene successions consists of six formal units (the Komarevo, Beloslav, Dikilitash, Aladan, Avren, and Ruslar formations) and one informal unit (glauconitic marker). For compiling an overall conception of the regional aspects (lithology, thickness, spatial distribution, and relationships) of the individual lithostratigraphic units and for illustration of their spatial distribution, a 3D lithostratigraphic model based on reinterpretation of individual borehole sections has been created. The model database was compiled by integration of the original lithological data from 338 borehole sections.

New data on the Paleogene lithostratigraphic units’ distribution in the Avren Step south of Varna and Beloslav Lakes based on borehole data and seismic profiles’ interpretation

“…The Beloslav and Dikilitash Formations show constant lithology throughout the area of their distribution. Characteristic for both units is that their color (pale-gray to gray-greenish) differs from the color, described in the type area (yellowish to lightbeige and white to gray respectively) as well as in Dobrogea (Valchev et al, 2018) and the Varna Plateau (Valchev et al, 2019). The Beloslav Formation demonstrates almost constant (with single exception) thickness (up to 15 m), while the Dikilitash Formation shows great varieties.…”

“…Some of the units demonstrate varieties in their lithological features, spatial distributions and relationships throughout the studied area. Valchev et al (2018Valchev et al ( , 2019 discussed the nomenclature, definition, and stratigraphic background of the units. A brief description, concerning the lithological features, thickness and stratigraphic relationships of each unit in the Avren Step, is given below.…”

A new view to the spatial distribution of the Paleogene lithostratigraphic units in the Goren Chiflik Horst based on borehole data

“…) Formations, the Dolni Chiflik Member of the Avren Formation, and the Ruslar Formation. Valchev et al (2018a and Vangelov and Sinnyovsky (2011) discussed the nomenclature, definition, and the stratigraphic background of the units. A brief description, concerning the lithological features, thickness, age and stratigraphic relationships of each unit in the Goren Chiflik Horst, is given bellow.…”

“…In series of articles, we published the results of the lithostratigraphic investigation of the Paleogene in Northeastern Bulgaria (Valchev et al, 2017(Valchev et al, , 2018aValchev, Dimitrov, 2018. They were contributions to the pioneering studies of the earlier researchers on this stratigraphic succession in this part of the country (Gočev, 1926(Gočev, , 1929(Gočev, , 1933(Gočev, , 1934Tzankov, 1936;Cohen, 1938;Tzankov, Beregov, 1940), their "followers" from the middle of the XX century (Mandev, 1955;Belmoustakov, 1960Belmoustakov, , 1962Belmoustakov, , 1968 and the "modern" authors Aladzova-Khrischeva (Aladjova-Khrischeva, 1984;Aladžova-Hrisčeva, 1990;Aladjova-Chrisčeva, 1991) and Juranov (in: Dzuranov, Darakchieva, 1986;Juranov, Pimpirev, 1989), who formalized the "horizons" of their predecessors according to the requirements of the Bulgarian Stratigraphic Code (Kojumdgieva et al, 1982).…”