Review of the main Black Sea rifting phase in the Cretaceous and implications for the evolution of the Black Sea lithosphere

Abstract

The Black Sea is a deep marine basin formed by lithosphere extension and active rifting in a back-arc tectonic setting, by general consensus, in the Cretaceous. Its present structural architecture, however, is mainly defined by compressional tectonics during the Cenozoic when large scale “basin inversion” reactivated extensional fault systems formed in the Cretaceous. Rifting during the Cretaceous is usually taken to represent the main process forming the present-day basin (that is, producing crustal thinning and concomitant subsidence prior to its modification during Cenozoic inversion). Rifting at this time took place within continental lithosphere that had been accreted to and, by the Cretaceous, formed part of the Eurasian lithospheric plate. The precise history of how and when pre-Cretaceous aged tectonic domains were accreted to Eurasia forming the continental lithosphere underlying the Black Sea is poorly known. A critical issue to the tectono-thermal evolution of the Black Sea basin with important implications for paleogeography and sedimentary depositional environments is the degree of crust (and lithosphere) thinning during Cretaceous rifting and whether oceanic or “sub-oceanic” crust was formed at that time. The main focus of this paper, in order to illuminate this issue, is on kinematic observations related to the Cretaceous (Albian-Cenomanian) rifting phase, including subsidence analysis, as well as the immediate post-rift sedimentation and stratigraphy. The results suggest that rifting during the Cretaceous was insufficient in its own right to reveal exhumed mantle or to promote ocean crust formation beneath the deep basins of the Black Sea. It is concluded that an important contribution to observed present-day crustal and lithosphere architecture of the Black Sea area are legacy extensional tectonic events affecting the area in pre-Cretaceous times, with implications for the Late Palaeozoic-Mesozoic paleogeography and paleotectonic evolution of this area.