The Oligocene-Miocene Maikop Series in the South Caspian and Kura Basins is the key petroleum source rock for both offshore and onshore petroleum development in Azerbaijan. The Maikop is a thick (up to 3 km) succession of silty mudstones containing up to 15% total organic carbon (TOC), but is greatly lacking diagnostic microfaunal assemblages useful for dating and stratigraphically constraining the deposition of the mudstone. Current stratigraphic constraints relying on microfaunal assemblages, radiostratigraphy, and chemostratigraphy are robust, but key information is still missing. This study adds numerical age data to Maikop stratigraphy through Re-Os geochronology. Of five sample suites analyzed from the Kura Basin of eastern Azerbaijan, one Re-Os data set produced significant range in 187Re/188Os vs 187Os/188Os space to yield an isochron of 17.2± 3.2 Ma. Other sample suites yield imprecise Re-Os age constraints as a result of variable initial 187Os/188Os values and limited range in 187Re/188Os vs 187Os/188Os space. The initial 187Os/188Os values of these data sets were compared with the known 187Os/188Os of seawater values for the past 70 million years to provide the best qualitative age constraints. Pre-Maikopian strata studied at Perikeshkul was found to coincide in 187Os/188Os values with the Eocene-Oligocene Transition (EOT) Os excursion, indicating deposition initiation of Maikopian strata following the EOT. Preservation of organic matter in intervals with initial 187Os/188Os values that deviate significantly from global 187Os/188Os values indicate basin restriction and the development of anoxia. High Os abundances, enrichment in detrital elements Al, Ti, Ga, Sc, and La, and changing basin circulation during the deposition of Maikop strata at 17.2 Ma may indicate the initial episodic uplift of the Greater Caucasus Mountains, changes in sediment provenance, or changing proximity to sediment source.



College and Department

Physical and Mathematical Sciences; Geological Sciences



Date Submitted


Document Type





Paratethys, Source Rock, Chemostratigraphy, Geochronology, Maikop