Rift Evolution and Crustal Structure in the Eastern Black Sea Basin from Long-offset Seismic Reflection Data

The Eastern Black Sea Basin (EBSB) is a deep extensional basin that opened during Late Cretaceous and the Early Tertiary in a back-arc setting, during the subduction of the Tethys Ocean. The presence of a thick sequence of sediments ( 10 km), which records the subsidence history, and the proximity to its conjugate rifted margins, reduce uncertainties in tectono-stratigraphic reconstructions. The EBSB is also a frontier in oil and gas exploration and, therefore, crustal types and their distribution are important parameters for thermal modelling of hydrocarbon maturation. However, whether the EBSB is underlain by stretched continental crust and/or oceanic crust, the distribution of crustal types, and the structures accommodating the stretching are all still debated.

In this study, we use long-offset seismic reflection data, acquired in 2011 by Geology Without Limits and ION GXT, to image the key elements of rift-basin settings such as thinned continental crust, tilted fault-blocks, syn- and post-kinematic sequences and the top of the acoustic basement and Moho. The spatial distribution of syn- and post-kinematic sequences and associated unconformities, provides an important record of the timing of rifting and helps to constrain the boundaries between crustal domains. Our identification of crustal domains and their distribution across the basin is also supported by an analysis of basement morphology. The basement reflection changes along a NW-SE direction, highlighting the presence of three different crustal domains from thinned continental crust in the NW to transitional crust and then "normal" oceanic crust in the SE. To further constrain the nature of the crustal domains and their boundaries, we integrate magnetic anomaly modelling. Additionally, stratigraphic relationships highlight the temporal and spatial migration of rifting during basin opening and are used to characterize rift evolution across this back-arc system.