«UDC: 564.3(497.11) UPPER MIOCENE FAUNA OF OREŠAC NEAR SMEDEREVO (SERBIA) GORDANA JOVANOVIĆ1, SLOBODAN KNEŽEVIĆ2, DRAGANA ĐURIĆ1, MARIANN ...»
Bulletin of the Natural History Museum, 2010, 3: 67-93.
Received 04 Aug 2010; Accepted 06 Oct 2010.
UPPER MIOCENE FAUNA OF OREŠAC
NEAR SMEDEREVO (SERBIA)
GORDANA JOVANOVIĆ1, SLOBODAN KNEŽEVIĆ2, DRAGANA ĐURIĆ1,
MARIANN BOSNAKOFF3, GORDANA PAUNOVIĆ4
Natural History Museum, Njegoševa 51, 11000 Belgrade, Serbia, e-mail: email@example.com, firstname.lastname@example.org 2 Department of Palaeontology, Faculty of Mining and Geology, University of Belgrade, Kamenička 6, Belgrade, Serbia 3 HAS-HNM Research Group for Paleontology, Budapest, Hungary e-mail: email@example.com 4 Museum of Smederevo, Omladinska 4, 11300 Smederevo, Serbia Near Smederevo, Orešac is one of the important Neogene localities described in literature, but it has not been preserved. During recent years, the field studies of the vicinity of Smederevo have shown that there are other preserved rich fossil sites with a mass appearance of the species Mytilopsis triangularis (Partsch) and Dreissena auricularis auricularis Fuchs and representatives of the family Lymnocardiidae. The most representative localities are Sastavci, Orešac-Udovice and Orešac-Udovice (New road to Požarevac). The site at Sastavci was described as a locality of particular importance for determining the stratigraphic cha- racteristics of this part of Central Paratethys, as it represents a direct continuation of the layers previously described as a faciostratotype of Upper Pontian under the name Orešac I. The locality Orešac-Udovice (New road to Požarevac) was described as the highest level of “Danube type (Groča-Smederevo) of de- velopment” of Upper Miocene.
Key words: Orešac-Udovice, Sastavci, Upper Miocene fauna, geoheritage.
JOVANOVIĆ, G.ET AL.: UPPER MIOCENE FAUNA OF OREŠAC68
INTRODUCTIONFor about a hundred years stratigraphers and paleontologists have researched and debated the stratigraphy of the younger Neogene, especially the correlation of strata between the large separated sedimentation basins (Central Paratethys and Eastern Paratethys). Alongside the classical strati- graphic methods such as lithological (sedimentological), tectonic, and biostratigraphic-paleontological (based on studies of macrofauna, micro-
fauna, and microflora), recently there has been an increase in new methods:
geophysical (paleomagnetic), new paleontological (nannoplancton, dino- flagellates etc.), radiometric dating, etc. However, in spite of the intro- duction of new methods and additional development of the old ones, there are still numerous unsolved problems in defining the age and correlation of Neogene sediments.
To find needed correlations in the stratigraphy of Neogene, stratotypes and facial stratotypes are used as etalons for comparing the synchronic Neogene sediments in characteristic profiles where the corresponding Neogene sediments are well-developed and rich in paleontological material.
During the field work in Serbia, a facial stratotype for the Portaferian substage of the Pontian (younger Upper Miocene) of Paratethys was determined in the vicinity of Smederevo as a “Danube type” of development (Stevanović 1951, Stevanović 1989). According to the cited author, the most important locality with fossils of the Danube type of development of Portaferian is Orešac I.
The studies performed over a century have shown that Pontian sediments cover most of the Danube area near Smederevo. The drilling results have shown that their thickness is about 150 m in the vicinity of Grocka and about 300 m in the vicinity of Smederevo (Stevanović 1951, Spajić 1977, Knežević et al. 1987). Almost all intercalating layers are rich in fossils. The diversity and effective preservation of fossil fauna, as well as its importance in international stratigraphic correlations, motivated new field studies and collecting of fossil material.
The vicinity of Smederevo is characterized by very brittle rocks, prone to erosion. The Pontian sediments are covered by Quaternary sediments with land mollusk fauna (Mitrović 2004) etc. The paleofauna was studied and collected several times during the last several years, leading to a description of two newly formed profiles named Sastavci and OrešacUdovice (New road to Požarevac) (Map. 1, Fig. 1, 4). The goals of the study were to determine the state of previously and newly discovered BULLETIN OF THE NATURAL HISTORY MUSEUM, 2010, 3: 67-93. 69 Pontian localities in the vicinity of Smederevo, collect the fossil material, and determine the stratigraphic, paleoecological and taphonomic characteristics of paleofauna. The authors of this paper have performed the first description and detailed research of the described localities. One part of the research was performed in collaboration with the Museum in Smederevo.
Map 1. - Location map of the fossil sites: Sastavci (1); Orešac-Udovice (Udovički potok) (2); Orešac-Udovice (New roud for Požarevac) (3); Orešac I (4); Orešac II (5); Dubočaj (Grocka) (6); Crveni Breg (Grocka) (7).
The material has been stored at the Natural History Museum in Belgrade and in the Museum of Smederevo. The Natural History Museum in Belgrade also includes the collections by Academy Members Petar Pavlović and Petar Stevanović. Part of this material is shown in plate (I, II).
JOVANOVIĆ, G.ET AL.: UPPER MIOCENE FAUNA OF OREŠAC70
OVERVIEW OF PREVIOUS STUDIES
Due to their richness in fossil material, the Pontian sediments in the vicinity of Grocka have been the subject of research by numerous paleontologists: Brusina 1894; Pavlović 1931; Stevanović 1951; Krstić et al. 1992, Jovanović 1988, 1998, 2003, Jovanović and Paunović 2005 etc.
They were separated as the layers with Congeria triangularis Partsch and placed in the Upper Congerian group. According to the identified species this locality is believed to be of the same age as Radmanest in Banat (Romania). The importance of these layers and layers with Congeria rhomboidea Hörnes was discussed by Pavlović (1923). Stevanović (1951) describes the localities Orešac I and Orešac II in detail, placing the sediments into the Upper Pontian (Portaferian), making a correlation of facies and horizons of the whole Paratethys, and discussing the problems of the upper and lower boundary of Pontian.
Over time it was shown that the same sediments were often given different names and this often confused paleontologists. Separation of stage and substage, instead of enabling more successful correlation in a wide international scope, brought more disagreements. The divisions and correlation of Neogene with Tethys and Paratethys were performed through the use of different methods in recent years, while the divisions based on malacofauna were almost completely neglected (Stevanović 1986). The stratigraphic characteristics were determined and correlations between certain localities of Central Paratethys made according to the characteristics of the bivalves (Stevanović 1951, 1978; Müller and Magyar 1992 etc.).
There were some suggestions about the revisions to the Pannonian-Pontian boundary. However, the question of Neogene divisions remains current to this day. Moving the Pontian stage into the Upper Miocene and its comparison with the Mediterranean Tortonian and Messinian (Rögl and Steininger 1983) would, according to Stevanović (1988), mean that Pliocene would be reduced by several million years, that is, the whole Pontian as defined now. The same author believes that the possible acceptable corrections could only include the Lower Pontian (Novorossian). In spite of the numerous uncertainties, the Portaferrian substage is officially accepted and included in the official stratigraphic division of Paratethys Neogene (Stevanović 1990c). The interest in the correlation of sediments from Late Miocene, their relationships with other basins and evolution and origin of their fauna is ongoing (Popov et al. 2006). Some magnetostratigraphic and chronostratigraphic correlations of sediments of Late Miocene were also made (Magyar et al. 1999b). The new stage Transdanubian, introduced by Sacchi and Horvath 2002, is considered by some authors to create even more problems.
BULLETIN OF THE NATURAL HISTORY MUSEUM, 2010, 3: 67-93. 71 At many localities in Serbia and Bosnia a mixture of Pannonian and Pontian mollusks was recorded at the Upper Pannonian-Lower Pontian boundary (Stevanović 1979-1980). This boundary was defined by the extinction of one type of large congeria and the appearance of another group of congeria with large shells. The lymnocardiids did not show such great sensitivity, and many species from Pannonian have survived into the Pontian. There are some transitionary mollusk forms: Mytilopsis czjzeki (Hörnes) (Upper Pannonian), M. czjzeki zagrabiensis (Stevanović) (Lower Pontian), M. zagrabiensis (Brusina) (Upper Pontian) etc. (sensu Stevanović 1979-1980). The more detailed stratigraphic divisions according to the biometric analyses of lymnocardiids were made by Müller and Magyar
1992. The examples of gradual evolution among the mollusks were described by Müller and Magyar 1992, Stevanović 1978 etc. According to the basic morphological characteristics of the genera belonging to the family, Dreisseniadae, Harzhauser & Mandić (2010) cite a list of taxa recorded in literature.
Stevanović and Mihajlović (1981) and Jovanović (1988, 1998) have published lists of identified species from certain localities (Požegovački Potok, Orešac-Udovice). The described geological profiles are included in localities very important for Serbian geoheritage. Jovanović (2003) presents the preliminary results of studies at the locality Orešac-Udovice (New road to Požarevac). Jovanović and Paunović (2005) have presented the results of the first studies at the newly discovered locality Sastavci.
Certain authors claim that the Upper Pontian sediments of GrockaSmederevo Danube area are connected with the Beli Potok Bay (Stevanović 1955) and Samar Hill (Knežević 1990) via Čot Hill.
DESCRIPTION OF THE GEOLOGICAL PROFILES
The studied area is dominated by fine-grained sandy sediments. The more detailed sedimentological studies of the sands (pontian sands, sensu Stevanović 1951) in the vicinity of Grocka and Smederevo have shown the existence of a slightly rounded shape. It was concluded that the minerals within the sands are most probably derived from metamorphic and eruptive rocks. The grains were also well-sorted by size. The smallest grains are in the sediments of Upper Pontian (Obradović and Rudolf 1958).
Most localities of Upper Miocene were recorded along the bank of the Danube. The localities of Orešac, Sastavci, Crveni Breg and Dubočaj begin with a layer of sandy clay that belongs to the lowest layer of Upper Congerian layers. The most common other sediments are sands and poorly
JOVANOVIĆ, G.ET AL.: UPPER MIOCENE FAUNA OF OREŠAC72 cemented sandstones. Their thickness increases toward the south. (Stevanović 1951, 1987, Anđelković et al. 1989).
The most instructive profiles, with numerous and diverse remains of fossilized organisms, i.e. flora, gastropods, bivalves, fish teeth and otoliths, were preserved in the area of Orešac near Smederevo. Presently there are three fossil branches: Sastavci, Orešac-Udovice and Orešac-Udovice (New road to Požarevac).
The geological profile of Orešac I (Orešac on the Danube, near Grocka) was described and placed in Upper Pontian (Lower Portaferian) (Stevanović and Mihajlović 1981). The locality of Orešac I, near the bridge, was described as a facies stratotype (Stevanović 1990c). Presently, the locality of Orešac is not exposed on the surface. The newly discovered locality of Sastavci has high significance for the geoheritage of Serbia. It is situated on the right bank of Sastavci Stream, 250 m from its confluence with the Danube. The length of the profile is about 30 m and the height about 20 m.
Fig. 1. - Outcrop of Upper Miocene sediments - Sastavci On the left bank of the same stream, besides the mollusks there was also a record of otoliths from family Scienidae (Stevanović 1951). The oldest recorded sediments are grayish-blue clays without fauna remains (layer 1), probably representing the lowest Upper Congerian layer, synchronous to the layer of gray clays at the profile of Crveni Breg near Grocka, with the malacofauna from the horizon with Congeria triangularis Partsch (Stevanović 1941). Above the clays there is a layer of fine-grained yellowish-gray sands with a small amount of clay (layer 2), with bivalve and gastropod shells. At the contact place of clays and sands there is a BULLETIN OF THE NATURAL HISTORY MUSEUM, 2010, 3: 67-93. 73 small spring. The following taxa were collected and identified: Dreissena auricularis auricularis Fuchs, Lymnocardium apertum (Münster), L. diprosopum (Brusina), L. cf. diprosopum (Brusina), L. zujovici Brusina, L. parazujovici Stevanović. L. decorum Fuchs, Lymnocardium sp., Mytilopsis triangularis (Partsch), Melanopsis decollata Stoliczka, Gyraulus radmanesti (Fuchs), Valvata variabilis Fuchs, Radix jaksici (Brusina).
Layer 2 includes an intercalating layer of gray clayey sands (2a), which is about 20 cm thick with numerous mollusk shells and fragments. This material is very soft and falls apart easily, so it is very difficult to separate
whole shells from the sediment. The following taxa were determined:
Lymnocardium penslii (Fuchs), L. schmidti (Hörnes), L. scabriusculum Fuchs, L. decorum Fuchs, Plagiodacna auingeri Fuchs, Melanopsis sturii Fuchs, Dreissena auricularis auricularis Fuchs, D. auricularis simplex Barbot, Valvata variabilis Fuchs, Melanopsis defensa Fuchs, Gyraulus radmanesti (Fuchs), Gyraulus sp.