A LATE PALEOZOIC EARLY MESOZOIC MARGINAL BASIN ALONG THE ACTIVE SOUTHERN CONTINENTAL-MARGIN OF EURASIA - EVIDENCE FROM THE CENTRAL PONTIDES(TURKEY) AND ADJACENT REGIONS

Remnants of two 'Palaeotethyan' oceanic basins are exposed in the Cent ral Pontides of northern Turkey, separated by a continental sliver and an oceanic arc. The southern basin corresponds to the main Tethys ('P alaeotethys'), which partially closed in Early Mesozoic time following northward subduction under the southern, active continental margin of Eurasia. The northern basin (Kure Complex) opened above the 'Palaeote thyan' subduction zone as a marginal basin, following rifting of a con tinental fragment (Istanbul fragment) from Eurasia. Marginal basin ope ning apparently dates from the Late Palaeozoic in the east (Kure basin ) and from the Triassic in the west (Kocaeli basin). Basin closure was achieved by southward subduction-accretion, in pre-Late Jurassic time s, leaving 'Neotethys' open to the south. Counterparts of the Kure Com plex are found in the adjacent Crimea (Taurian Series), Istranca (Zabe rnevo Complex), Dobrogea (Nalbant flysch) and Caucasus (pre-Late Juras sic Southern Slope Basin) regions. Basin opening was accompanied by oc eanic crust genesis, at least in the Pontides and Caucasus. Closure be fore Mid-Jurassic time was achieved by subduction-accretion processes, whereby oceanic crust and deep-sea sediments (including sulphides) we re detached and structurally assembled, while oceanic basement was sub ducted. Marginal basin opening and closure is seen as one in a series of events along a long-lived, active south Eurasian continental margin .