Post-Glacial Terraces of The Marmara Sea and Water Exchange Periods

Semi enclosed Marmara Sea is a passage between the Aegean Sea (Northeastern Mediterranean Sea) and the Black Sea. The Marmara Sea is connected to the Black Sea and Aegean Sea through the Istanbul Strait (Bosphorus) and Canakkale Strait (Dardanelles), respectively. Despite the fact that the late Pleistocene-Holocene connections between the seas have been explored by many scientists, there are still uncertainties about the nature and timing of the connections. Within the scope of this study, a new approach has been displayed for post-glacial connections between the Black Sea, Marmara Sea and Aegean Sea. This study is based on 80 shallow seismic reflection lines, multibeam bathymetric data and 15 short gravity cores collected from the northeastern shelf of the Marmara Sea (between Silivri and Golden Horn). The sea bottom and sub-bottom morphology have a highly chaotic structure at the exit of the Buyukcekmece/Kucukcekmece lagoons and further east near the Marmara-Istanbul Strait junction. This chaotic bottom and sub-bottom surface morphologies are mainly controlled by the structure of the basin, current regime of the shelf, coastal drainage systems and by the sea/lake water level changes controlled by climate and the sill depths of the two straits, which in turn determined the water exchange between the seas. The sedimentological interpretation of the seismic reflection profiles and core sediments have allowed us to distinguish five stratigraphic units (S1-S5) and four sedimentary layers (A-D) over the acoustic basement. The lower stratigraphic unit and sedimentary layer are separated from the overlying acoustic basement by a chaotic to parallel and by a high amplitude seismic reflector. Seaward dipping units of the acoustic basement are inferred to be the seaward continuation of the Oligocene-Upper Miocene units widely exposed on land. The presence of three different marine terraces distinguished (T1-T3) along the northeastern shelf of the Marmara Sea have been associated with the six different curves of the post-glacial sea-level changes. From statistical point of view, the most significant terraces occur from -78 m to -80 m (T1), -58 m to -62 m (T2) and -28 m to -32 m at (T3). Considering the global sea level curves, these terraces can be dated 9.25, 12.25 and 13.75 Cal kyr BP, respectively

The structural elements and tectonics of the Lake Van basin (Eastern Anatolia) from multi-channel seismic reflection profiles

This study analyzed multi-channel seismic reflection data from Lake Van, Eastern Anatolia, to provide key information on the structural elements, deformational patterns and overall tectonic structure of the Lake Van basin. The seismic data reveal three subbasins (the Tatvan, northern and Ahlat subbasins) separated by structural ridges (the northern and Ahlat ridges). The Tatvan basin is a tilted wedge-block in the west, it is a relatively undeformed and flat-lying deep basin, forming a typical example of strike-slip sedimentation. Seismic sections reveal that the deeper sedimentary sections of the Tatvan basin are locally folded, gently in the south and more intensely further north, suggesting a probable gravitational “wedge-block” instability, oblique to the northern margin. The northern subbasin, bounded by normal oblique faults, forms a basin-margin graben structure that is elongated in a northeast-southwest direction. The east-west trending Ahlat ridge forms a fault-wedged sedimentary ridge and appears to offset by reverse oblique faults forming as a push-up rhomb horst structure. The Ahlat subbasin is a fault-wedged trough fill that is elongated in the west-east direction and appears as a horst-foot graben formed by the normal oblique faults. The northeast-southwest directed northern ridge is a faulted crestal terrace of a sublacustrine basement block. Its step-like morphology, in response to the downfaulting of the Tatvan basin, as well as its backthrusted appearance, indicates the normal oblique nature of the bounding faults. The lacustrine shelf and slope show distinctive stratigraphic features; progradational deltas, submerged fluvial channels, distorted and collapsed beddings and soft sediment deformation structures, characterizing a highly unstable nature of shelf caused by strong oblique faulting and related earthquakes. The faulting caused uplift of the Çarpanak spur zone, together with the northeastern Erek delta, deformation of deltaic structures and subsequently exposing the shelf and slope areas. The exposed areas are evident in the angular unconformity surface of the Çarpanak basement block with the northeastern Erek delta and thinned sediments. The uplift resulted in the asymmetric depositional emplacement of the southeastern delta that is controlled by a series of ramp anticlines/low angle reverse faults. The Deveboynu subbasin and Varis spur zone form wide fault-controlled depressions with thick sediments that are elongated in the north-south direction. These subbasins appear as a small pull-apart boundary formed by normal oblique faults at the western end of the southeastern delta

Prevalence of cervical cytological abnormalities in Turkey

Objective: To evaluate retrospectively the prevalence of cervical cytological abnormalities in patient records obtained from healthcare centers in Turkey. Method: Demographic characteristics and data on cervical cytological abnormalities were evaluated from patients who underwent flap tests in healthcare centers in 2007. Results: Data were collected from 33 healthcare centers totaling 140 334 patients. Overall, the prevalence of cervical cytological abnormalities was 1.8%; the prevalence of ASCUS, ASC-H, LSIL, HSIL, and AGC was 1.07%, 0.07%, 0.3%, 0.17%, and 0.08%, respectively. The prevalence of preinvasive cervical neoplasia was 1.7% and the prevalence of cytologically diagnosed invasive neoplasia was 0.06%. Conclusion: The abnormal cervical cytological prevalence rate in Turkey is lower than in Europe and North America. This might be due to sociocultural differences, lack of population-based screening programs, or a lower HPV prevalence rate in Turkey. (C) 2009 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved

Prevalence of cervical cytological abnormalities in Turkey

Objective: To evaluate retrospectively the prevalence of cervical cytological abnormalities in patient records obtained from healthcare centers in Turkey. Method: Demographic characteristics and data on cervical cytological abnormalities were evaluated from patients who underwent flap tests in healthcare centers in 2007. Results: Data were collected from 33 healthcare centers totaling 140 334 patients. Overall, the prevalence of cervical cytological abnormalities was 1.8%; the prevalence of ASCUS, ASC-H, LSIL, HSIL, and AGC was 1.07%, 0.07%, 0.3%, 0.17%, and 0.08%, respectively. The prevalence of preinvasive cervical neoplasia was 1.7% and the prevalence of cytologically diagnosed invasive neoplasia was 0.06%. Conclusion: The abnormal cervical cytological prevalence rate in Turkey is lower than in Europe and North America. This might be due to sociocultural differences, lack of population-based screening programs, or a lower HPV prevalence rate in Turkey. (C) 2009 International Federation of Gynecology and Obstetrics. Published by Elsevier Ireland Ltd. All rights reserved