Spatial and temporal evolution of rifting and continental breakup in the Eastern Black Sea Basin revealed by long-offset seismic reflection data

Abstract

The age and distribution of the syn-rift and early post-rift infill records the spatial and temporal distribution of extension and breakup processes in a rift basin. The Eastern Black Sea Basin (EBSB) is thought to have formed by back-arc extension during Cretaceous to Early Cenozoic time. However, a lack of direct constraints on its deep stratigraphy leaves uncertainties over the time, duration and location for rifting and breakup processes in the basin. Here we use the enhanced imaging provided by 2D long-offset seismic reflection profiles to analyze the deep structural and stratigraphic elements of the EBSB. Based on these elements, we infer the presence of two distinct Late Cretaceous syn-rift units, recording initial extension (rift stage 1) over the continental highs (Shatsky Ridge and the Mid Black Sea High), followed by strain localization along the major basin-bounding faults and rift migration towards the basin axis (rift stage 2). Overlying these units, Palaeocene(?)-Eocene and Oligocene units show a syn-kinematic character in the NW, with evidence for ongoing extension until Oligocene time. Towards the SE, these sequences are instead post-kinematic, directly overlaying a basement emplaced during breakup. We interpret the Palaeocene(?)-Oligocene units to record the time spanning from the initiation of breakup (Late Cretaceous-Palaeocene, in the SE) to the end of extension (Oligocene, in the NW). The first ubiquitously post-rift infill is the Lower Miocene Maykop Formation. Our results highlight the along-strike temporal variability of extension and breakup processes in the EBSB.