The revision of Quaternary stratigraphy of the Sombor and Subotica artesian well borehole profiles (Bačka, Vojvodina, Serbia)

Abstract

The results of stratigraphy of the Sombor and Subotica boreholes were first results of geological examination of borehole material from Vojvodina published by Halaváts in 1895. These geological profiles, alongside the borehole profile in Zrenjanin, were recognized as “standard” profiles for Quaternary geology and stratigraphic correlation pertaining to Vojvodina. However, the results of taxonomical revisions for malacologic material, published in 1977 by Krolopp and which presented significant changes in stratigraphy, have not been implemented in the results of geological mapping/surveying. According to new advances and results regarding Quaternary stratigraphy, Lower Pleistocene sediments can be better defined using Pleistocene Corbicula beds, the Viviparus boeckhi Horizon and the results yielded by this paper.In the case of the Sombor borehole, the Lower Pleistocene was defined at a depth from 48.13 m to 149.5 m, according to its palaeonological record (molluscan assemblage). The Lower- and/or Middle Pleistocene were defined as the interval between a 35.45 m and 48.13 m depth, based on sedimentology (lignite) and malacology. The interval from 15.21 m to 35.45 m depth was identified as Pleistocene, based on superposition and palaeontological material. The yellow quartz sand horizon at 9.74 m–15.21 m remains undefined. The Holocene yellow silty-clay horizon, which ascends to a 9.74 m depth, was identified as Holocene, according to the palaeontological content of the same sediments found in the brickyard in the vicinity of Sombor.In the case of the Subotica borehole, the Lower Pleistocene – based on palaeontological records – was defined at a depth between 99.6 m and 124.5 m. The depth from 2.2 m to 99.6 m could not be exactly identified as Pleistocene, while Holocene quicksand ascended to a 2.2 m depth.