An offshore-onland transect across the north-eastern Black Sea basin (Crimean margin): Evidence of Paleocene to Pliocene two-stage compression

Abstract

The tectonic evolution of the Black Sea (BS) is a subject of debate, there are several unsolved questions: 1) the timing and the spatial progression of the BS basin opening and 2) the timing of Cenozoic shortening along the northern margin of the Eastern BS basin. The timing of the main compressional deformations, related to the inversion of the Greater Caucasus (GC) basin, is assumed to be Oligo-Miocene. However, Late Cretaceous/Early Paleocene shortening, linked to the final closure of the northern branch of the Neotethys, is also suggested. The Crimean Mountains (CM), to the north of the Eastern BS, is one of the key areas to investigate in order to fix the tectonic evolution of the BS. To precise the timing of the Cenozoic shortening of the Eastern BS, we focus on an integrated onshore/offshore transect from the Eastern CM to the Sorokin Trough (north of Eastern BS). We use newly collected stratigraphic and structural data from the Eastern CM, and a new interpretation of multichannel seismic lines. We define 1) the offshore seismic stratigraphy and constrain the relative chronology of deformations, 2) the age of seismic units by correlation of the seismic data with the Subbotina-403 well log, and 3) we construct an on-to-off shore transect of Eastern CM - northern Eastern BS region. Our results evidence a polyphased Cenozoic compression in the northern part of the Eastern BS: 1) Paleocene-Earliest Eocene and 2) Oligocene-Miocene (Maikopian). Normal faults appear to be related to a formation of the foreland basin, instead of evidencing the Eastern BS Cretaceous rifting. Finally, this study allows precising the shortening phases within Eastern CM and Eastern BS since the Early Paleocene, linking them to the Neotethys closure and the GC tectonic evolution.