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Abstract
A palynological study of 239 outcrop samples and their sedimentological context was undertaken on the Pliocene Productive Series in the Kirmaky and Yasamal valleys, eastern Azerbaijan. The Productive Series is primarily a representation of the palaeo-Volga and forms the main hydrocarbon-producing reservoirs in the South Caspian Basin. Most sands are interpreted as fluvial, based on sedimentary characteristics. Mudstone and siltstones often contain freshwater and brackish assemblages interpreted as ‘Caspian lake’ transgressions, indicative of rapid Caspian Sea level change during the Pliocene. Most samples contain rich assemblages including pollen, spores, dinoflagellate cysts, algae and fungal bodies. Common tree pollen elements include Pinus, Alnus, Betula, Carya, Juglans, Pterocarya, Quercus and Ulmus, which all occur in present-day vegetation or pollen records from the Caucasus or Urals. Herbaceous pollen includes Amaranthaceae, Asteraceae (including Artemisia), Ephedra and Poaceae, commonly found in the drier Caspian regions. The dinoflagellate cysts include ‘Peri-paratethyan endemic’ taxa such as Caspidinium rugosum and Spiniferites cruciformis. ‘Pannonian’ species such as Thalassiphora balcanica, Romanodinium areolatum and Spiniferites oblongus confirm the persistence of these taxa into the early Pliocene in Eastern Paratethys, around five million years later than their first documented presence in Central Paratethys. ‘Caspian lake’ influences diminish up-section, as indicated by a progression from brackish to freshwater and sub-aerial conditions. Productive Series deposition was mainly driven by the combined effects of lake level and catchment climate. The principal hydrocarbon reservoir sands were deposited as a result of increased catchment humidity, whereas drying conditions led to reduced coarse clastic input and deposition of alluvial plain mudstones. Productive Series deposition terminated with the onset of the marine-influenced Akchagyl Series, which spans the Plio-Pleistocene boundary. The lowermost sediments of the Akchagyl Series are freshwater in origin and grade up-section into marine beds containing dinoflagellate cysts of Arctic affinity.
Acknowledgements
The authors would like to thank CASP, United Kingdom, for permission to publish this paper. The fieldwork for this study was undertaken in various phases between 2000 and 2002, and the assistance of many people is gratefully acknowledged, either for help with the fieldwork itself and/or with subsequent data interpretation. The study would not have been possible without support and encouragement from Mike Simmons (Halliburton) and Steve Lowe (formerly BP), and the manuscript was significantly improved by attentive comments from three reviewers, including that of Jean-Pierre Suc. Applied Petroleum Technology (UK) Ltd. are thanked for allowing the use of a fluorescence photomicroscope. Artwork on most of the figures was carried out by Alison Davies of The Mapping Company, UK.
Disclosure statement
No potential conflict of interest was reported by the authors.
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Notes on contributors
Keith Richards
KEITH RICHARDS has worked commercially as a palynologist since 1985, first for Robertson Research for 11 years, based in North Wales, Indonesia and Singapore, and then with his own company (KrA Stratigraphic) since 1996. He has maintained an academic interest throughout that time with around 20 peer-reviewed articles and many more conference presentations with particular emphasis on palynology and stratigraphy of the Greater Caspian Region. He has been a Guest Researcher at The University of Amsterdam (Institute for Biodiversity and Ecosystem Dynamics) since 2016, obtaining his PhD from UvA in 2018. He is currently an Honorary Senior Research Fellow (Geography and Planning) at the University of Liverpool.
Stephen J. Vincent
STEPHEN VINCENT received his PhD from Liverpool University in 1993. His PhD focussed on the sedimentology, stratigraphy and provenance of palaeovalley deposits within the Spanish Pyrenees. He joined CASP in 1993 and has subsequently worked on aspects of clastic sedimentology, regional geology, syn-tectonic sedimentation and basin evolution in China, Siberia, West Africa, Azerbaijan, Armenia, Albania and all countries surrounding the Black Sea. Steve has been Black Sea Project leader since 1999 and became Chief Geologist in 2019. He co-ordinates CASP's work in the Caspian region.
Clare E. Davies
CLARE DAVIES is a geologist and sedimentologist who obtained her PhD in 2000 from the University of Leeds, based on the Miocene-Pliocene evolution of the Ganges Delta. She then worked at CASP, Cambridge, researching the stratigraphic evolution of Paratethys and other regions. She is an experienced geoscientist with more than 20 years working in petroleum geology, stratigraphy, sedimentology and seismic interpretation in major exploration companies, most recently as Australian Exploration Manager at BHP, Perth, Australia.
David J. Hinds
DAVID HINDS obtained his PhD from Aberdeen University in 2002, entitled “Sedimentology and depositional setting of the Neogene Productive Series, Apsheron Peninsula, Azerbaijan”. His PhD was part funded by CASP. He has since worked as a geologist and sedimentologist for several exploration companies, most recently for Shell International Limited.
Elmira Aliyeva
ELMIRA ALIYEVA is Head of Department at the Scientific Research and Design Institute of the State Oil Company of the Azerbaijan Republic (SOCAR) and Head of Department at the Geology and Geophysics Institute of the Azerbaijan National Academy of Sciences, in Baku, Azerbaijan. She is co-author of numerous reports and publications on many aspects of the geology of the Caspian region.