MIDDLE PLEISTOCENE SMALL MAMMAL FAUNAS OF EASTERN AND WESTERN EUROPE: CHRONOLOGY, CORRELATION

. Many new very important Middle Pleistocene small mammal localities of Europe were discovered during the last decades. These new data permit to divide the Middle Pleistocene geological sequences of Eastern and Western Europe and carried out the correlation between them. However, there are some difficulties connected with the incongruity of mammal appearance in different parts of Europe. In this paper we would like to discuss all these problems using Middle Pleistocene small mammal data and to present the possible biostratigraphical scheme for the whole Europe.

ABSTRACT. Many new very important Middle Pleistocene small mammal localities of Europe were discovered during the last decades. These new data permit to divide the Middle Pleistocene geological sequences of Eastern and Western Europe and carried out the correlation between them. However, there are some difficulties connected with the incongruity of mammal appearance in different parts of Europe. In this paper we would like to discuss all these problems using Middle Pleistocene small mammal data and to present the possible biostratigraphical scheme for the whole Europe.  [Mikhailesku, Markova, 1992;Markova, 2007]. So the faunas of this key section reflected the natural events of the most part of the Middle Pleistocene (Fig. 1). These faunas expressed the significant evolutional changes in different phylogenetic lines of Arvicolidae: Prolagurus -Lagurus, Microtus (Stenocranius) hintoni-gregaloides -M. (S). gregalis and others. The different taphonomy of Kolkotova Balka main horizons (fluvial deposits and fossil soils) didn't permit to reveal the transition between the rooted voles of Mimomys genus (the ancestral form of water vole Arvicola) and the un-rooted voles of Arvicola genus. All localities with Mimomys were found in fluvial older deposits. The different fossil soils overlying the fluvial deposits didn't include the remains of water voles Arvicola (or its ancestor form Mimomys intermedius) what could be explained by their taphonomy.
There are several other very principal Middle Pleistocene small mammal localities situated on the south-west of the Russian Plain in Prut and Danube River basins. The faunas were described in Nagornoe, Suvorovo, Ozernoe, Plavni and many others localities. These localities as a rule characterize only one stage of Middle Pleistocene: Il'inka Interglacial, Muchkap Interglacial, Likhvin Interglacial and Kamenka Interglacial. Most of them include the fauna of the Likhvin Interglacial. The significance of these materials for stratigraphy also is very high. All of these localities were found in the liman and lake deposits and include not only mammal remains but also brackish-water mollusks what permits to carry out the straight correlation between the continental and marine deposits of the Russian Plain and the Black Sea [Mikhailesku, Markova, 1992].
Dnieper basin. There are several Middle Pleistocene localities of small mammals are known from the Dnieper basin, mostly from the middle part of basin. They are connected with the fluvial deposits of IV terrace of Dnieper. The localities Gunki and Pivikha are situated on the left bank of Dnieper; the Chigirin locality is situated on the right bank [Markova, 1982] (Fig.1).
Gunki locality was studied by the several methods (geological, pedological, palynological, malacological methods). Also the palaeomagnetic investigation of deposits had been done [Velichko et al., 1982]. This outcrop includes the deposits of second part of the Middle Pleistocene and the Upper Pleistocene. The Dnieper (=Zaalian) till is registered here. The Romny and Kamenka paleosols were described below the Dnieper till. Fluvial thickness occurred below the loess-paleosol sequence. The fluvial deposits of IV terrace are correlated with the Likhvin Interglacial by the palynological and mammalian data. The small mammal remains were discovered in the 3 facieses of alluvium close by age. The rich fauna didn't include the teeth of rooted voles Mimomys and Borsodia. There are no also remains of archaic voles (with "pitymys" triangles) such as Microtus (Terricola) [Gubonina, 1982]. Malacological materials show on Early Euksinian age of mollusk fauna. Gunki section is a unique one by the completeness of the palaeontological data [Markova, 1982]. The localities Pivikha and Chigirin include similar small mammal faunas by the species composition . In last years the small mammal faunas with archaic Arvicola were found in the deposits related to interval, which follows Muchkap interglacial and cooling which is next after  [Markova, 2004]. The Kamenka fossil soil is located higher in this section. The Rybnaya Sloboda fauna includes Arvicola сantiana, Lagurus transiens-lagurus, Clethrionomys rufocanus and others. In lower Volga basin (Chernyi Yar locality) more evolved fauna was described with more progressive Arvicola and Lagurus [Alexandrova, 1976]. Similar fauna of small mammals was found near Spasskoe village in the middle Volga basin [Markova, 2007].

Western Europe
The Central and Western European small mammal record is from a number of geographically scattered, in many cases isolated localities. Rich, well-known early Middle Pleistocene assemblages are from localities such as Voigtstedt (Gemany) and West Runton (England) . Long sequences are almost non-existent. An exception is the Kärlich sequence, exposed in a quarry located in the Neuwied Basin (Germany), with on top of the Tertiary clays Quaternary deposits gravels of the Rhine and Moselle rivers and an alternation of loess, loess-like, and slope deposits and tephras (ashes, pumices) which originate from extinct volcanoes located in the neighbouring East Eifel volcanic field dating from the late Early Pleistocene to the Holocene [Boenigk, Frechen, 2001]. Several stratified mammalian faunas, within which the Mimomys -Arvicola transition occurs, were collected from the Pleistocene sequence (Kärlich main section -Kä A -H) exposed in the Kärlich pit. The older faunas Kä C -F are characterised by the presence of Mimomys savini; the oldest representatives of the water vole, Arvicola terrestris cantiana, were recovered in the rich fauna from Kä G. The faunal assemblages from the Kärlich sequence together with the faunas from the same region (Miesenheim I and Ariendorf ) form a reference for the early Middle Pleistocene faunal history to which faunas such as Mauer and Mosbach (Germany) can be correlated [van Kolfschoten, 1990]. Central European faunas dating to the Elsterian (Oka) Glaciation are poorly known. The same applies to the Holsteinian (Likhvin) faunas. The Schöningen locality (Germany) yielded an extensive collection of small mammal remains dated to post-Elsterian age [van Kolfschoten, 2012]. The oldest assemblage from this site most probably has a Holsteinian age; however, this assemblage is rather poor. The mammal fauna from the socalled Reinsdorf Interglacial (locally defined), the second interglacial after the Elsterian, is very rich. This fauna is characterised by the presence (in a low quantity) of early Middle Pleistocene relicts (Talpa minor and Drepanosorex) as well as rather primitive water vole Arvicola molars indicating that the age of the fauna predates many wellknown late Middle Pleistocene faunas such as Weimar-Ehringsdorf (Germany) and Maastricht-Belvédère (The Netherlands) [van Kolfschoten, 1985] with a more advanced Arvicola record and with relicts.  We need to mention some differences in the first appearance of new small mammal taxa in Western and Eastern Europe. So, there are un-known Central European faunas with Mimomys remains which correspond to the complicated interval between the cold stage synchronous to the Don Glaciation and the Elster Glaciation. Only archaic water voles Arvicola cantianus were discovered in these faunas. On the contrary there are several important well-known mammal localities in Eastern Europe (in the Dniester and Don basins) with evolved Mimomus (M. savini) which related to the Muchkap Interglacial. This Interglacial took place between the Don and Oka Glaciations. The first un-rooted water voles Arvicola cantianus appeared only in the very end of this complicated interval during the Ikoretsk Interglacial. Till now this phase was revealed only in the Don basin.

DISCUSSION
The future studies of small mammal faunas from the different regions of Europe and also the correlation of main stratigraphical horizons with mammal localities permit to establish most reliable correlations of Middle Pleistocene small mammal faunas of Eastern and Western Europe.
Described analysis of the Middle Pleistocene small mammal faunas could help to reconstruct and to date the natural events of Middle Pleistocene for the territory of whole Europe and to reveal the similarities and un-similarities in Arvicolidae evolution in the different parts of Europe.