Geology of the Cretaceous sedimentary basins of the Western Pontides

The southern passive margin of the oceanic Western Black Sea Basin consists of two tectonic units, the İstanbul Zone and the Central Pontides. These units are delimited by a fundamental, north–south Araç–Daday shear zone juxtaposing totally different basement rock groups and covering later Mesozoic sedimentary rocks. To the west of this shear zone the İstanbul Zone is covered by a sedimentary succession deposited in a southerly deepening continental margin basin. This basin was bisected lengthwise during the Maastrichtian forming the Zonguldak Basin in the northwest and the Ulus Basin in the southwest. Both of these basins were deformed in the Early Cainozoic. To the east of the Araç–Daday shear zone, the northerly deepening Sinop Basin dominates the architecture of the Pontides in the north. It began forming by extension in the Barremian and was destroyed by a single‐phase north–south compression in the Late Eocene–Oligocene. After the juxtaposition of the Central Pontides and the İstanbul Zone, an E–W trending extensional magmatic arc was established on these sedimentary basins in response to northward‐subducting Neotethys to the south. This magmatic arc, which began during the Turonian, gave rise to the Western Black Sea oceanic back‐arc basin. None of the basins in the Pontides is simple. They show a complex evolution responding to different rifting and closure events with much, as yet unspecified, strike‐slip movement. Copyright © 1999 John Wiley & Sons, Ltd.