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    Öğe
    Episkopeia Kalesi(Büyükçekmece-Ahmediye)
    (2020) Aydıngün, Şengül G.; Kaya, Hakan; Stanıslawskı, Blazej; Aydıngün, Haldun; Enez, Ayberk; Özdemir, Oktay; Öniz, Hakan
    Bu yazıda, İstanbul’un batısında Büyükçekmece Gölünün 8 km. kuzeyinde yer alan Ahmediye Kalesi olarak kayıtlara geçmiş kalenin, VI. Yüzyılda İmparator Justinianus (MS 527-565) tarafından yaptırılan Episkopeia Kalesi olduğu üzerinde durulmaktadır. Kale, bölgedeki verimli tarım arazilerini Trak, Avar ve Bulgar akınlarından korumak amaçlı yaptırılmıştır. Bu makale Kale ile ilgili ilk detaylı çalışmanın sonucunda hazırlanmıştır.
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    Öğe
    First note on Holocene coquinite on Thrace (Black Sea) coast of Turkey
    (Elsevier Science Bv, 2012) Erginal, Ahmet Evren; Ekinci, Yunus Levent; Demirci, Alper; Elmas, Elmas Kirci; Kaya, Hakan
    In this paper, preliminary results concerning the nature, subsurface structure and age of carbonate-cemented coquinite extending along a 1.5-km long and 40-m wide loose coquina beach on the Thracian (west Black Sea) coast of Turkey are presented. An Electrical Resistivity Tomography (ERT) survey showed that the coquinite has a maximum thickness of about 2 m and comprises seaward dipping buried 20 m-wide slabs under beach materials at the backshore. Cemented by low-magnesian calcite, the coquinite contains various bivalvia, benthic foraminifera, calcareous nannofossils or coccoliths and quartz sands. Diagenesis of the coquinite occurred as the result of sequential cementation, starting with the precipitation of micritic envelops typical of a marine phreatic zone. This early stage was followed by pore-lining cements and bladed rims composed of equal-sized subhedral and anhedral crystals of calcite, suggesting evidence of meteoric phreatic and meteoric vadose environments, respectively. Calibrated values from radiocarbon dating of four bulk samples of bivalvia revealed that the coquinite shells were deposited between 3730 and 2850 years BP. During that period the sea-level was similar to the present at an early stage then dropped to 2 m due to Phanagorian regression (between 3200 and 2200 BP), which is evidenced by consecutive cementation patterns of distinctive origin. (C) 2012 Elsevier B.V. All rights reserved.
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    Öğe
    Formation of Holocene paleosols in a relict sand dune sequence at Kıyıköy, Türkiye
    (Tubitak Scientific & Technological Research Council Turkey, 2025) Erginal, Ahmet Evren; Bozcu, Mustafa; Yakupoglu, Nurettin; Akbas, Abdullah; Kaya, Hakan; Tunc, Ismail Onur
    The paleoclimatic indicators from a relict dune and paleosol sequence observed south of K & imath;y & imath;k & ouml;y Port, NW T & uuml;rkiye, provide insights into the variable paleoclimatic conditions in the western Black Sea coastal zone over the last 4700 yrs BP. The relict dunepaleosol sequence consists of reddish-brown coarse sands with abundant shells and overlying paleosol. Radiocarbon dating of Donax trunculus shells collected from the lowest part of the relict dune revealed the onset of sand deposition 4689 +/- 123 yrs ago. The dark-colored paleosol layer, with an Rb/Sr ratio of 0.008, yielded an age of 287 +/- 32 yrs cal BP. These findings indicate that the paleosol developed around the 1700s, during one of the coldest phases of the Little Ice Age. This layer is followed by a brown-colored buried soil, indicating a short-lived humid and rainy period, as evidenced by an Rb/Sr ratio of 0.42.
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    Öğe
    Historical record of metals in Lake Kucukcekmece and Lake Terkos (Istanbul, Turkey) based on anthropogenic impacts and ecological risk assessment
    (Taylor & Francis Ltd, 2019) Kukrer, Serkan; Cakir, Caglar; Kaya, Hakan; Erginal, Ahmet Evren
    The objective of this study was to determine the vertical distribution of metals and organic carbon in lakes Kucukcekmece and Terkos, which are located in different areas near Istanbul and are affected by different environmental factors. The aim was also to specify the metal input, its sources, and the ecological risk over the last 700 years. For analysis, core sediment samples were taken from the bottom of each lake, sliced into 2-cm sections, and analyzed for multiple elements, organic carbon, carbonate, and chlorophyll degradation products. It was determined that Lake Kucukcekmece is threatened by domestic and industrial pollution. To solve this problem, a treatment plant was commissioned in 2012 for the treatment of urban and industrial wastes. In addition, natural gas has been the preferred fuel for the last two decades in Istanbul and this has changed the pollutant profile. On the other hand, Lake Terkos faces possible risks of Mn, P, and As inputs because of fertilizer use in nearby agricultural fields.