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The Lower Carboniferous flysch of the Istanbul Zone in Turkey is an over 1500 m thick turbiditic sandstone-shale sequence marking the onset of the Variscan deformation in the Pontides. It overlies Lower Carboniferous black cherts and is unconformably overlain by Lower Triassic continental sandstones and conglomerates. The petrography of the Carboniferous sandstones and the geochronology and geochemistry of the detrital zircons and rutiles were studied to establish the provenance of the clastic rocks. The sandstones are feldspathic to lithic greywackes and subgreywackes with approximately equal amounts of quartz, feldspar and lithic clasts. The amount of quartz and lithic fragments decreases upwards in the sequence at the expense of feldspar. The lithic fragments are dominated by intermediate volcanic rocks, followed by metamorphic and sedimentary rock fragments. Coarse lithic fragments are generally granitoidic. In the discrimination diagrams, sandstone samples lie mainly in the field of dissected arc. A total of 218 detrital zircons and 35 detrital rutiles from four sandstone samples were analysed with laser ablation ICP-MS. The detrital zircons show a predominantly bimodal age distribution with Late Devonian to Early Carboniferous (390 to 335 Ma) and Cambrian-Neoproterozoic (640 to 520 Ma) ages. The remaining 9 % of the analysed zircons are in the 1700-2750 Ma range; zircons of the 700-1700 Ma age range are absent. The REE patterns and Th/U ratios of the zircons are consistent with a magmatic origin. With one exception (Neoproterozoic), the rutile ages are Late Devonian-Early Carboniferous and their geochemistry indicates that they were derived from amphibolite-facies metamorphic rocks. Sandstone petrography and detrital zircon-rutile ages suggest one dominant source for the Lower Carboniferous sandstones: a Late Devonian to Early Carboniferous magmatic and metamorphic province with overprinted Neoproterozoic basement. Late Devonian-Early Carboniferous magmatic and metamorphic rocks are unknown from the Eastern Mediterranean region. They are, however, widespread in central Europe. The Istanbul Zone is commonly correlated with the Avalonian terrranes in central Europe, which collided with the Armorican terranes during Carboniferous times, resulting in the Variscan orogeny. The Carboniferous flysch of the Istanbul Zone must have been derived from a colliding Armorican terrane, as indicated by the absence of 700-1700 Ma zircons and by Late Devonian-Early Carboniferous magmatism, typical features of the Armorican terranes. This suggests that during Carboniferous times the Istanbul terrane was located close to the Bohemian Massif and has been translated by strike-slip along the Trans-European Suture Zone to its Cretaceous position north of the Black Sea.

The disastrous 1999 earthquakes in Turkey have spurred the international community to study the geometry and behavior of the North Anatolian Fault (NAF) beneath the Marmara Sea. While the area is considered mature for a large earthquake, the detailed fault geometry below the Marmara Sea is uncertain, and this prevents a realistic assessment of seismic hazards in the highly‐populated region close to Istanbul. Two geological/geophysical surveys were recently conducted in the Marmara Sea: the first in November 2000 with the R/V Odin Finder, and the second in June 2001 with the R/V CNR‐Urania. Both were sponsored and organized by the Institute of Marine Geology of the Italian National Research Council (CNR), in cooperation with the Turkish Council for Scientific and Technical Research (TUBITAK) and the Lamont‐Doherty Earth Observatory of Columbia University Multi‐beam bathymetry, multi‐channel seismic reflection profiling, magnetometry high‐resolution CHIRP sub‐bottom profiling, and bottom imaging were carried out with a remotely operated vehicle (ROV). Over 60 gravity and piston cores were collected.

The Maritsa River in the Balkans, over 500 km long, flows at present into the northern Aegean Sea. Geological and geomorphological data indicate that it was flowing into the Marmara Sea until about 1.5 Ma, and was diverted into the Aegean Sea following coseismic uplift along the North Anatolian Fault. Seismic reflection sections in the Marmara Sea indicate the presence of up to 2.5 km thick fluviatile to limnic Upper Miocene–Quaternary sediments, probably supplied by a Palaeo-Maritsa river. The drainage diversion cut off the sediment supply, with the result that the terrigeneous sediments of the Marmara Sea were depressed to a water depth of 1150 m.