An integrated study on the Late Miocene Tuģlu formation – palaeoecological, palaeoclimatic and palaeogeographical interpretation (Çankiri Basin, Central Anatolia, Turkey)

Within the framework of the EUROCORES Topo-Europe programme the VAMP (Vertical Anatolian Movements Project) Project, an international and interdisciplinary research team (APVV-ESF-EC-0009-07 and IGAG-CNR TA.P05.009.003) has achieved detailed sampling and study of key stratigraphic sections in the Çankiri Basin (Central Anatolia). Ostracods, benthic foraminifera, nannoplancton, charophytes, molluscs, fish remains, palynomorphs and micromammals have been recovered from the 21m thick Tuģlu section. Biostratigraphy based on small mammals is still in progress, because new data from VAMP sampling during last year point to an age of rodent assemblage (MN7-8) older than the previously published data (MN10). The rodent assemblage composition is characterized by the dominance of Byzantinia cf. bayraktepensis and unusually diversified Gliridae (genera Myomimus, Myoglis, Muscardinus and Glirulus). The genus Myoglis was not previously known from Anatolia. The less common taxa are Democricetodon, Keramidomys and Spermophilinus. The association of rodents from Tuglu suggests humid and forested environment. Insectivores have not yet been processed. Both magnetic mineralogy and magnetic susceptibility analyses were carried out and the variations of magnetic parameters (SIRM, SIRM/k, IRM 1/0.1) along the section were studied. These parameters display a link with the distribution of freshwater ostracods probably related to humid climatic inputs. Most likely, the Tuglu formation deposited in a continental setting characterised by permanent water bodies affected by strong salinity and depth oscillations. The molluscs from the middle and upper part of the section are characterised by terrestrial, freshwater and low-oligohaline gastropods and bivalves represented by the genera Lymnaea, Bithynia, Melanopsis, Dreissena, Potomida and Helicidae, showing alternating open land, lacustrine and fluvial conditions. A diversified charophyte assemblage (Nitellopsis, Lychnothamnus and Chara) confirms the existence of a permanent water body in the middle part of the section. Since dating is still in progress, it is difficult to estimate sedimentation rates and to distinguish seasonal or inter annual salinity changes from changes in salinities due to other inputs. To better understand such oscillations, high-resolution sampling of a 350-cm-long section has been performed. The palynological record documents subtropical climate (Cathaya, Engelhardia) and in the lower part of the profile changes in low sporomorphs concentration (Pinaceae) are recorded opposite to higher percentages of halophytes (Chenopodiaceae) and dinoflagellates. Ostracods, benthic foraminifera, molluscs, charophytes, fish remains and pollen have been recovered. Palaeomagnetic sampling was also performed and all samples display a normal polarity. The ostracod assemblage is characterised by the alternate dominance of Cyprideis sp. and Ilyocypris spp., with Leucocythere sp., Zonocypris membranae quadricellae, Heterocypris salina and Candonidae as accompanying species. The benthic foraminifera appear suddenly in the Cyprideis dominated samples and disappear as much abruptly. Quinqueloculina, Miliolina Trisegmentina and Varidentella, tolerating hyperhaline conditions, dominate the foraminiferal assemblage. Species rapidly increase in size with aberrant coiling up to top of profile. In the lowermost part of the profile, abundant exemplars of Perfocalcinella fusiformis and Palaeogene and Cretaceous redeposited calcareous nannofossils were recovered. Foraminifera and calcareous nannoplancton presence in the lower part of the profile provide two hypotheses about this sequence origin.