Trans-border (north-east Serbia/north-west Bulgaria) correlations of the Jurassic lithostratigraphic units

Abstract

Herein, correlations of the Jurassic sediments from NE Serbia with those of NW Bulgaria are made. The following Jurassic palaeogeographic units: the Eastern Getic, the Infra-Getic and the Moesian Platform are included in the study. The East Getic was studied in the outcrops near Rgotina, where the sedimentation started in the Hettangian and continued during the Callovian-Late Jurassic and is represented by platform carbonates. The Infra-Getic is documented by the sections of Dobra (Pesača) and the allochtonous sediments near the Štubik. Very important for the Infra-Getic are the Late Jurassic volcano-sedimentary deposits of the Vratarnica Series, which crop out near Vratarnica Village. The Jurassic Moesian platform was studied in the sections near D. Milanovac and Novo Korito (Serbia) and in their prolongation in NW Bulgaria into the Gornobelotintsi palaeograben. Very important are the correlation in the region of Vrška Čuka (Serbia) and Vrashka Chuka (Bulgaria) - Rabisha Village (Magura Cave). A revision of the Jurassic sediments on the Vidin palaeohorst, which were studied in the Belogradchik palaeohorst, Gorno-Belotintsi palaeograben, Belimel palaeohorst and the Mihaylovgrad palaeograben, is made. The sedimentation on the Vidin palaeohorst started during different parts of the Middle Jurassic, and in the Mihaylovgrad palaeograben during the Hettangian (Lower Jurassic) where the sediments were deposited in relatively deeper water conditions. To south, the relatively shallow water sediments deposited on the Jurassic Vratsa palaeohorst on the southern board of the Mihaylovgrad palaeograben are described

Palaeoenvironments of northwestern Bulgaria and northeastern Serbia during the Jurassic

“…The latter palaeotectonic unit is a southern extension of the Lower Danubicum from NE Serbia (see Kräutner and Krstić, 2003), and these equivalent units were developed after the Old Cimmerian Orogeny on the territory of present-day NW Bulgaria and NE Serbia. The Vidin Jurassic Horst was limited from the west by the Izdremets Jurassic Graben (the southern prolongation of the Infra-Getic in East Serbia sensu Tchoumatchenco et al, 2011), and from the SSE by the Mihaylovgrad Early-Middle Jurassic Graben, respectively (Sapunov et al, 1988). The Vidin Horst and the Mihaylovgrad Graben, as well as the Lower Danubicum, took part of the Jurassic Moesian Platform, on which various depositional environments were developed.…”

“…Heterogranular oligomict sandstones, conglomerates, clays and coal-bearing shales, sporadically containing Cycadophyta and referred to the Vrashka Chuka Formation, were deposited (Sapunov et al, 1988). The first marine shallow sublittoral environments, with sandy-pebbly bottom and agitated water, were imposed, into a narrow strip with NW-SE trend, on the southern and central part of the Vidin Horst, in which the oligomict sandstones and conglomerates of the Kichera Formation and the Staro Selo Clastites were accumulated (Tchoumatchenco et al, 2011). Poor fossil assemblages of bivalves and less common brachiopods (often fragmented), as well as poorly preserved single ammonites and belemnites, occur as extreme rarities in the clastic rocks.…”

“…However, at the end of the early Bajocian, thin "tongues" of sandy limestones to calcareous sandstones, referred to the Polaten Formation, were formed into narrow areas to the east and the south of Belogradchik Town. Equivalent strata, called Štubic Clastites, were accumulated into separate localities to the south of the town of Donji Milanovac (Tchoumatchenco et al, 2011). These sediments were deposited in shallow to moderately-deep sublittoral environments with calcareous bottom and agitated water.…”

“…3a, b). The latter environments resulted in the accumulation of marl-limestone de- posits, referred to the Bov Formation in NW Bulgaria (Sapunov et al, 1988), and called "Posidonia" beds in NE Serbia (Tchoumatchenco et al, 2011). At that time, several normal regional faults, with E-W trends, were presumably also present and two areas of reduced sedimentary influx, resulting from non-deposition or submarine washout, were developed.…”

“…However, the evidence contained in these papers has long been confined to the Bulgarian/ Serbian state border, and what is beyond the border, in northeastern Serbia, has been known mainly from the publications of Serbian geologists (e.g., Andjelković and Petković, 1975;Andjelković et al 1996;Radulović et al, 1997). During the previous decade, successful correlations between the Jurassic lithostratigraphic units in NW Bulgaria and NE Serbia were made (Tchoumatchenco et al, 2006a(Tchoumatchenco et al, , 2006b(Tchoumatchenco et al, , 2008(Tchoumatchenco et al, , 2010a(Tchoumatchenco et al, , 2010b(Tchoumatchenco et al, , 2011. A result of this is that correlations between the Bulgarian and Serbian Jurassic lithostratigraphic successions have now attained the highest levels of reliability and detail.…”