The Signature of the Mediterranean Messinian Salinity Crisis in the Black Sea and Caspian Basins: a Comparison
Gabor Tari, Mohammad Fallah, and Walter Kosi
The Black Sea and Caspian basins are located in the area of the Eastern Paratethys. In the late Miocene, between about 6 and 5.3 Ma a major base level fall was described in both basins. The base-level fall and subsequent isolation from the world seas were interpreted by many as the result of the Messinian Salinity Crisis (MSC) well known in the Mediterranean region.
The Pliocene Productive Series of the South Caspian Basin has been described as a major lowstand wedge within an underfilled lacustrine basin. This mega-lowstand wedge, relative to the preexisting Miocene and subsequent Pleistocene shelf margins, deposited in a time span of about 2.6 m.y, after the initial base-level drop of about 1.5 km magnitude. The overall thickness of the lacustrine sediments deposited during this time reaches 6 km containing several prominent reservoir intervals in the Azeri and Russian sectors of the Caspian Basin. The various reservoir intervals developed in fluvial, deltaic and lacustrine facies associations. The MSC affected the various basin segments of the Caspian region differently, depending on the pre-existing basin margin configuration and sediment entry points. We suggest that the broadly age-equivalent formations of the Lower Productive Series in the Iranian sector are underexplored as the best reservoir units such as deltaic and slope siliciclastic formations may lie in the poorly known deepwater area.
Similarly to the seismic stratigraphic signature of the MSC in the Caspian Basin, large-scale erosional features were observed along the Western Black Sea shelf in wells and on seismic reflection profiles. Various observations around the basin suggest a significant sea-level drop, but with a much debated magnitude (between 0.1- 2.2 km), as the manifestation of the MSC in the Black Sea Basin.
Truncated reflectors beneath the inferred MSC unconformity indicate the erosional removal of significant parts of the underlying Mesozoic and Cenozoic deposits in the the Romanian and Bulgarian shelfal areas. The correlative MSC unconformity in the deepwater parts of the basin is often overlain by mass-transport complexes as the products of the earliest lowstand system tracts. The upper parts of the MSC lowstand wedge are interpreted to be developed in a better, reservoir-quality deepwater facies such as in basin floor fan and slope fan settings. As a recent deepwater discovery in the Romanian sector of the western Black Sea highlighted the importance of Miocene reservoirs, the unexplored reservoir intervals within the MSC lowstand wedge, similarly to its age-equivalent Caspian analogue, may have an exploration potential.
AAPG Search and Discovery Article #90161©2013 AAPG European Regional Conference, Barcelona, Spain, 8-10 April 2013