Messinian canyons in the Turkish western Black Sea
Several canyons are observed along the Turkish margin of the western Black Sea that are associated with a prominent unconformity and interpreted to be the manifestations of the sea-level fall during the Messinian salinity crisis in the Mediterranean. In this study, their morphology, geometry and fill characteristics, as well as downslope evolution, are compared and contrasted using four 3D seismic surveys and some 2D regional seismic lines.
Two types of canyon morphologies are observed in the study area: (1) shelf incising and (2) blind. Located in the western part of the study area and deeply incised into a wide shelf, the Karaburun Canyon extends roughly in a SW–NE direction. The fill of the canyon is almost absent on the shelf, where the canyon base is downlapped by a series of Pliocene clinoforms. A thin fill appears on the upper slope, which gets thicker towards the lower slope. The eastern part of the study area is dominated by a series of blind canyons (Boğaziçi canyons). They are typically confined to the continental rise, with their heads hardly reaching the lower slope. Their fill is entirely characterized by mass-transport complexes (MTCs).
It is concluded that during the Messinian lowstand, the sediments within the Karaburun Canyon bypassed the wide shelf and were funnelled down to the continental rise and abyssal plain through the slope, which was followed by progradation of the basin margin during the relative sea-level rise in the Pliocene. A minimal imprint by tectonics in that particular area might have helped establish more stable conditions for the development of a relatively mature sediment dispersal system extending from the hinterland down to the basin centre. In this area, the shelf-slope morphology was dominantly shaped by the depositional geometries of the sedimentary packages. Being fully confined to the continental rise, the Boğaziçi canyons are situated in an area where shelf-slope morphology is governed by the Late Cretaceous volcanic arc. Parallel with the coastline, these volcanic edifices have created fairly steep dips; thus, leading to the development of an unstable basin margin and favouring MTC deposition at least since the Early–Middle Miocene. The width and relief of the canyons display a decreasing trend from west to east, which may be attributed to their relative distance from a possible drainage system in the vicinity of the Bosporus that might have acted as the major sediment supplier during this period.
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The Black Sea remains one of the largest underexplored rift basins in the world. Future success is dependent on a better understanding of a number of geological uncertainties. These include reservoir and source rock presence and quality, and the timing of migration of hydrocarbons relative to trap formation. An appreciation of the geological history of the Black Sea basins and the surrounding orogens is therefore key. The timing of basin formation, uplift of the margins, and of facies distribution remain issues for robust debate. This Special Publication presents the results of 15 studies that relate to the tectono-stratigraphy and petroleum geology of the Black Sea. The methodologies of these studies encompass crustal structure, geodynamic evolution, stratigraphy and its regional correlation, petroleum systems, source to sink, hydrocarbon habitat and play concepts, and reviews of past exploration. They provide insight into the many ongoing controversies concerning Black Sea regional geology and provide a better understanding of the geological risks that must be considered for future hydrocarbon exploration.