The Ypresian to Lutetian marine record in NW Turkey: a revised biostratigraphy and chronostratigraphy and implications for Eocene paleogeography

Abstract

The Eocene sedimentary units in the Kocaeli and Armutlu peninsulas and İznik-Geyve region (northwest Turkey) consistof marine siliciclastic and carbonate deposits, locally intercalated with volcaniclastic rocks and tuffs (Middle Eocene MagmaticRocks-MEMR). The record of larger benthic fauna (LBF) and pelagic microfossils, such as planktonic foraminifera and calcareousnannoplankton, combined with lithological description, indicate a wide spectrum of depositional environments ranging from shallowto deep-marine. These deposits contain in situ and/or allochthonous assemblages of orthophragminids, nummulitids, subordinaterotaliids, and sparse alveolinids. The in situ assemblages (mainly orthophragminids) point to several episodes of shallow marinedepositional conditions during a) early Ypresian (SBZ 5-7 and 7-9), b) late Ypresian (SBZ 10-11), c) early Lutetian (SBZ 13), and d)middle Lutetian (SBZ 14-15). Upper Ypresian (Cuisian) deposits with rich LBF accumulations are the most ubiquitous, recognizedacross a wide region from the Thrace Basin to Central Anatolia. Lower Lutetian deposits, on the other hand, occur in a limited area onlynear the town of Şile, on the coast of the Black Sea. Orthophragminids immediately below the first volcaniclastic beds of the MEMRconstrain the initiation of the volcanism to the latest Ypresian or around the Ypresian/Lutetian boundary. The LBF assemblages from theclastic intercalations of the MEMR are referred to SBZ 14-15 and indicate that the marine realm in the Armutlu and Kocaeli peninsulaspersisted until middle Lutetian. Since then, continental conditions have prevailed in the region, while a marine realm has developed inthe Thrace Basin during the late Middle to Late Eocene and Oligocene. The deep-marine Eocene deposits with pelagic microfossils andallochthonous LBF are mostly confined to the Ypresian. The allochthonous orthophragminids in these deep-marine deposits are alsopresented here to give a broader picture of their occurrence in NW Turkey.