Middle Pleistocene bivalves of the İznik lake basin (Eastern Marmara, NW Turkey) and a new paleobiogeographical approach

Abstract

_ Iznik Lake is a tectonically originated basin mainly controlled by the E-W trending middle strand of the North Anatolian Fault (NAF) system. Pleistocene sediments occurring in front of the faults are well exposed both in the northern and in the southern shorelines of the basin. In this study, two endemic brackish water bivalve species, Didacna subpyramidata Pravoslavkev 1939 and Didacna nov. sp. were found in the oldest terrace of the northern Pleistocene sequence. Having characterized morphology, these species serve as stratigraphic indicators in the regional Pleistocene stratigraphy of the Ponto-Caspian region, and thus are well correlated to the assemblages of the early Khazarian subhorizon (Middle Pleistocene). Hence, these data demonstrate that the early Khazarian brackish water sea covered the study area. Additionally, a model for the formation of the basin is proposed: the _ Iznik lake basin was a gulf of the former Marmara Sea in the early Khazarian, connecting the Marmara to the Black Sea and the Caspian Sea. The subsequent regional prograding uplifts, main dextral strike-slip fault and many normal faults of the NAF Zone cut off the marine connections to the basin, leading to its present location and topographic level.

Postglacial floodings of the Marmara Sea: molluscs and sediments tell the story

“…Other authors found a variety of ages for the lacustrine stage of the Marmara Basin, including connected/disconnected episodes with the Black Sea (Table 2). Low oxygen isotope ratios from 23 ka to 16 ka (Vidal et al 2010) indicate the fresh-brackish nature of the Black Sea Basin outflow (Çağatay et al 2000, 2009, 2015Eriş et al 2007Eriş et al , 2008Eriş et al , 2011McHugh et al 2008;Vidal et al 2010;Taviani et al 2014).…”

“…13-18 ka (Andrussov 1896(Andrussov , 1900İslamoğlu and Chepalyga 1998;Çağatay et al 2000;İslamoğlu 2002;Bahr et al 2005;Hiscott et al 2007;Badertscher et al 2011;Eriş et al 2011;Taviani et al 2013Taviani et al , 2014. During the transition from the last glacial maximum (LGM) to the Holocene, the glacioeustatic sea-level rise drove major hydrological and sedimentary processes in the Marmara Basin (Aksu et al 1999;Çağatay et al 1999, 2003, 2009, 2015Ergin et al 1999;Hiscott et al 2002Hiscott et al , 2007Kaminski et al 2002;Major et al 2002Major et al , 2006Kerey et al 2004;Eriş et al 2007Eriş et al , 2008Eriş et al , 2011McHugh et al 2008;Vidal et al 2010) and the Bosphorus/Dardanelles straits (Gökaşan et al 2005(Gökaşan et al , 2006(Gökaşan et al , 2008(Gökaşan et al , 2010.…”

From Tethys to Eastern Paratethys: Oligocene depositional environments, paleoecology and paleobiogeography of the Thrace Basin (NW Turkey)

“…Quaternary deposits are represented by terrestrial sediments in most parts of the basin and by fossiliferous marine terraces surrounding the coasts of the Marmara region. These terraces reflect strong sea level changes due to the glacial/interglacial rhythm and tectonic movements of the western continuation of the east-west trending North Anatolian Fault System (NAF) (Sakınç and Yaltırak 1997;Emre et al 1998;_ Islamoglu and Tchepalyga 1998;_ Islamoglu et al 2001;_ Islamoglu 2008). The about 10 m thick succession comprises a very indistinct and highly bioturbated interbedding of 20-40 cm thick sandy-marly limestones and 5-15 cm thick sandy marls with a rich echinoderm-mollusc-foraminifers assemblage.…”

First note on marine-like cementation of Late Holocene beachrock, Iznik Lake (Turkey)

“…Unlike many studies which pointed to increased water levels during the Pleistocene era (Ardel 1953;Tanoglu and Erinc, 1956) or sea-water connections (Islamoglu, 2009;Nazik et al, 2010), there are very limited field data that suggest Holocene water-level variations in Iznik Lake.…”