Contrasting Pliocene fluvial depositional systems within the rapidly subsiding South Caspian Basin; a case study of the palaeo-Volga and palaeo-Kura river systems in the Surakhany Suite, Upper Productive Series, onshore Azerbaijan

摘要: Abstract The South Caspian Basin contains major hydrocarbon reservoirs within the largely Early Pliocene Productive Series. This paper describes and contrasts outcrops of uppermost ∼500 m series (the Surakhany Suite) deposited by two main fluvial systems that supplied Azeri margin basin. Sedimentary facies and, for first time from Series, palynological analyses document channel belt complexes, sheetflood overbank flood plain to lake environments. Series on Apsheron Peninsula, Azerbaijan, was predominantly north palaeo-Volga river system. It displays an overall fining-upward trend, such Suite at Lokbatan is dominated mudstone. Siltstone coarser-grained sediments make up 28% section. Channel bodies are average 1.5 m thick form 13% succession. In sub-surface ratty wireline log responses also indicate siltstone sandstone thin bedded, with SP-derived net-to-gross sand ratios ∼0.35–0.40. succession in Kura sourced west palaeo-Kura a coarsening-upward middle upper Babazanan coarser 52% characterised numerous stacked laterally continuous 5.8 m comprise 42% outcrop. Basin, have blocky character 0.26–0.38. These values similar calculated volumes outcrop (44%). data, including multivariate analyses, show controls palynomorph distribution degree or lacustrine influence, subaerial exposure salinity. Despite their more lithic nature, sandstones derived system along Kurovdag-Babazanan-Neftchala trend better petrophysical properties than those Peninsula its offshore continuation. probably due coarser-grain size. This, combined greater body thickness, would suggest axis forms most promising part sector exploration