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Yayın A Preliminary note on depositional characteristics and optical luminescence age of a marine terrace, strait of Canakkale, Turkey(Coastal Education & Research Foundation, 2013-01) Avcıoğlu, Mustafa; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Kapan Yeşilyurt, Sevinç; Yiğitbaş, ErdinçThis preliminary study investigated the depositional features and optical luminescence age of marine terrace sediments located on the east coast of the Strait of Canakkale, Turkey. With regard to depositional setting, the studied sequence is formed mostly of shallow marine deposits rich in quartz and oysters as well as other accessory minerals and various fossil sea shells. In vertical section, the sequence is characterized by two different stratigraphic units, i.e. a 1.50-m-thick sandy to gravely bottom unit (unit A) and an overlying 2.5-m-thick fossiliferous zone (unit B). On the basis of optically stimulated luminescence (OSL) age estimations obtained from six sampling levels from bottom to top, we determined superimposed cycles of deposition during interglacials from 246.47 +/- 25.32 ka (unit A) at MIS 7 to 127.48 +/- 8.91 ka (unit B) at MIS 5.Yayın Records of repeated drought stages during the Holocene, Lake Iznik (Turkey) with reference to beachrock(Pergamon-Elsevier Science Ltd., 2016-07-15) Öztürk, Muhammed Zeynel; Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Demirci, Alper; Ekinci, Yunus Levent; Cürebal, İsa; Avcıoğlu, Mustafa; Öztürk, TuğbaThe cement fabrics, subsurface nature and optically stimulated luminescence age of beachrocks along the shores of Lake Iznik in NW Turkey were studied within the context of Holocene lake level changes. With a maximum thickness of 1.5 m, the low-angle (average 5-10 degrees) beds are composed of coarse grains and small gravels and extend up to 5 m offshore at their most lakeward extremities. Cement textures on and around the poorly-rounded grains are made up of micrite envelopes and meniscus bridges as well as acicular aragonite rims. Geoelectrical resistivity sections taken from a representative location along the beach where the beds have maximum thickness showed that the sand-buried beds are followed up to about 24 m landward. Based on the OSL ages of 33 samples, the cemented beds occurred at four drier periods of the following: Pre- and Early Holocene (dated to 15-9 ka), Holocene Climatic Optimum (7.9-5.6 ka), Middle Holocene (4.9 ka-2.8 ka) and Late Holocene (2.0 ka-0.9 ka).Yayın First note on marine-like cementation of Late Holocene beachrock, Iznik Lake (Turkey)(Versita, 2012-03) Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Öztürk, Muhammed Zeynel; Yiğitbaş, Erdinç; Bozcu, Mustafa; Avcıoğlu, Mustafa; Öztürk, BeyhanMicro-fabric characteristics and optically stimulated luminescence (OSL) dating results are presented to discuss the controlling agents and timing of beachrock cementation on the fresh-water Iznik Lake shoreline. The beachrocks are made up of grain-supported polygenic conglomerate containing 20.42% carbonate with encrusted grains, basically as micrite coatings, isopachous aragonite rims, cryptocrystalline void fills and meniscus bridges. The optical ages of twelve samples yielded ages that range from 4.226 +/- 0.569 ka on the lowermost beds to 0.706 +/- 0.081 on the uppermost. This is the first report of precipitation of marine-like cements in Iznik Lake. The abundant aragonite-dominated cement is likely indicative of precipitation-prone dry evaporative conditions from the climatic optimum to the last millennia.Yayın Cementation characteristics and age of beachrocks in a fresh-water environment, Lake Iznik, NW Turkey(Elsevier Science BV, 2012-12-01) Erginal, Ahmet Evren; Güneç Kıyak, Nafiye; Öztürk, Muhammed Zeynel; Avcıoğlu, Mustafa; Bozcu, Mustafa; Yiğitbaş, ErdinçThis paper focuses on the cement characteristics and optical luminescence age of late Pleistocene-Holocene beachrock, exposed on the southeast shore of freshwater Lake Iznik in northwest Turkey, based on field observations, various spectroscopic analyses and optical dating results. The studied beachrock is a poorly-sorted coastal conglomerate composed mostly of gravels derived from surrounding volcanic rocks and marbles as well as quartz and carbonate grains. We identified different types of cements; dominated by micritic envelopes, bladed isopachous aragonite rims, void fills, radial aggregates and meniscus bridges, implying no single origin. Cementation characteristics indicate that marine-like cement micro-fabrics may occur in freshwater lake environments where the lake-water chemistry favors carbonate precipitation. OSL data revealed the existence of older beachrock dating back to 20.2 ka, together with younger Holocene-age beachrock of between 5.6 and 2.4 ka. This suggests that younger beachrocks have been superimposed on older cemented carbonates through the removal of carbonates by wave motion (splash and spray) during lower lake level conditions.
