Factors controlling the morphological evolution of the Çanakkale Strait (Dardanelles, Turkey)

Seismic profiling, bathymetric and physical oceanographic data collected from the Çanakkale Strait revealed that the morphological evolution of the strait has been controlled by tectonic activity, and sediment erosion and deposition. Sediments in the strait have been sourced mostly by rivers draining the Biga Peninsula during lowstand periods. In highstand periods, by contrast, deposits in the strait were reworked by currents. The seafloor morphology of the Çanakkale Strait is also controlled by a sequence of factors ranging from tectonics to current erosion and deposition. Channel deposits overlying the basement are being eroded at the narrower, meandering central section of the strait (the Nara Passage) due to high current velocities. The eroded sediments are deposited in the relatively linear and wider, northern and southern sectors of the strait exposed to low current velocities. As a result, the high-energy areas are more deeply incised due to the erosion, whereas deposition elevates the seafloor in the areas exposed to lower current energy. Three strike-slip faults, which possibly relate to the activity of the North Anatolian Fault Zone, are responsible for the irregular shape of the strait and this, in turn, controls the current velocity along the strait. The high-energy conditions probably commenced with the latest invasion of Mediterranean waters some 12 ka b.p., and have continued as a two-layered current system to the present day.     

Distribution and texture of the bottom sediments in a semi-enclosed coastal inlet, the Izmit Bay from the eastern sea of Marmara (Turkey)

Thirty-one surficial sediment samples were collected from the floor of Izmit Bay with a grab onboard the R/V Bilim in summer 1987 and analysed for their grain size, total carbonate, and organic carbon distribution.Low calcareous-terrigenous mud (2–45% CaCO₃) with a relatively high silt percentage was the principal sediment type found on the floor of Izmit Bay. Sediments rich in sand and gravel usually occur in the narrow and shoal areas of the bay, where biogenic and topography-related hydrodynamic conditions are dominant factors controlling the nature of bottom deposits. The carbonates are made up almost entirely of the remains of calcareous organisms. Organic carbon concentrations of the sediments (0·35-1·62%) are probably associated with the high primary production rates in this region. Thus, the rates of sedimentation in the Izmit Bay calculated from the organic carbon and primary productivity data are estimated to be up to 70 cm/1000 years.     

Sea-level changes and related depositional environments on the southern Marmara shelf

Petrographic data obtained from 182 surface sediment samples together with the available bathymetric data are used to investigate the effects of the last major sea-level changes on shelf evolution in the southern Sea of Marmara. Grain-size analysis reveals the presence of at least three belts or zones which are rich in coarse-grained (sand and gravel) sediments. These coarse-grained belts which are up to 45 km long, 15 km wide, show up to 20 m of relief and are presently found at 40–80 m (average 60 m) water depths. Based on microscopic examination and residual analysis, the sediments from these belts are interpreted as indicators of high-energy shallow waters where detrital siliciclastics, with some benthic contribution, accumulated. The presence of a 62–65 m deep sill in the Çanakkale Strait and the consideration of sea-level curves would suggest that the Marmara shelves must have been subaerially exposed down to −65 m water depths for about 10,000 yrs (22,000–12,000 yrs B.P.), sufficient time to modify former shelf topographies and form such bottom relief. While difficult to date, we believe that coarse-grained belts found on the southern Marmara shelf must be relict (i.e., former shorelines, beaches) and their formation is largely related to low stands of sea-level during the Late Pleistocene regression and early Holocene transgression. However, the available high-resolution seismic profiling data suggest that the neotectonism in this seismically active Sea of Marmara plays an important role to explain the raise of these older shorelines to their present levels on the sea-floor.     

Late Quaternary evolution of the Çanakkale Strait region (Dardanelles, NW Turkey): implications of a major erosional event for the postglacial Mediterranean-Marmara Sea connection

Seismic and bathymetric data from the Çanakkale Strait and its extensions onto the shelves of the Marmara and Aegean seas indicate that the strait was formed mainly by an erosional event. Four seismic units are observed on seismic profiles. The lower two of these (units 4 and 3) constitute the basement of a regionally widespread erosional unconformity (ravinement), which developed during marine isotope stage 2 (MIS 2). The two upper units (units 2 and 1), which overlie the ravinement surface, form a higher-order sequence. Sequence stratigraphic analysis indicates that units 2 and 1 deposited as lowstand and highstand systems tracts respectively, since the end of MIS 2. The transgressive systems tract is represented by a major erosional event which occurred throughout the Çanakkale sill area when the Mediterranean-Marmara Sea connection and, hence, the Çanakkale Strait was formed. The existence of the erosive ?arköy Canyon along the shelf edge of the southern Marmara Sea demonstrates that the flow direction causing the erosion was from south to north, thus proving that it was produced by Mediterranean water flowing over the sill into the Marmara Sea basin.     

A new methodology for evaluating coastal scenery: fuzzy logic systems

Coastal scenery evaluated by utilization of selected landscape components was subjected to a fuzzy logic systems approach. Twenty-six top-rated parameters were identified from a literature search/questionnaire surveys carried out in Malta, Turkey and the UK and coastal scenery investigated at 57 sites. A coastal scenic evaluation checklist system was finalized and consisted of assessment parameters based on a five-point scale ranging from low to high attribute values. Coastal user parameter preferences and priorities for these parameters were obtained by a questionnaire perception study (n = 270) given to both locals and visitors. Assessment parameter weights were calculated from this public perception survey via matrices relating to the selected landscape components. For each of the 26 parameters, a membership-graded matrix was established to counteract potential errors in assigning grades to the parameters when one has to give a unique number to the attribute value. To overcome subjectivity and quantify uncertainty, fuzzy logic mathematical methodology was adopted to this checklist approach. This enabled an Evaluation Index (D) value to be calculated, establishing a 5-class evaluation system. Class 1 scenery (extremely attractive natural site) had D values > 0.85; Class 2, between 0.85 and 0.65; Class 3, between 0.65 and 0.4; Class 4, between 0.4 and zero; Class 5 (very unattractive, intensively developed urban) below zero.