Spatial and Temporal Evolution of Rifting and Continental Breakup in the Eastern Black Sea Basin Revealed by Long-Offset Seismic Reflection Data

摘要

The age and distribution of the synrift and early postrift in fill 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 2-D 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 synrift 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 toward the basin axis (rift stage 2). Overlying these units, Palaeocene(?)-Eocene and Oligocene units show a synkinematic character in the NW, with evidence for ongoing extension until Oligocene time. Toward the SE, these sequences are instead postkinematic, 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 postrift in fill is the Lower Miocene Maykop Formation. Our results highlight the along-strike temporal variability of extension and breakup processes in the EBSB.