13) The modern Volga delta: an analogue for the Pliocene Productive Series in the offshore Caspian Sea ?

By KEITH RICHARDS (1), STEPHEN LOWE (2), DAN FINUCANE (2) & ANDREW BOWMAN (2)  

(1) KrA Stratigraphic, Deganwy, UK

(2) BP Exploration, Sunbury on Thames, UK

Draft Abstract for Houston Conference (Geologic problem solving with Microfossils)

Mar 15-18 2009

The modern Volga delta: an analogue for the Pliocene Productive Series in the offshore Caspian Sea ?

The paleo-Volga is a major hydrocarbon play in the Pliocene Productive Series of the Caspian region. Extensive palynological analyses have been carried out, mainly on core, from the ACG and Shah Deniz fields, offshore Azerbaijan . Palynological data are also available from shallow cores taken in the modern Volga delta, which enable direct comparison between the Pliocene and present-day (Holocene) deltas. The pollen flora in the modern delta reflects the huge and varied Volga catchment, encompassing boreal and temperate forest, steppe, semi-desert and desert, as well as the extensive delta regions, which include varied dry and wetland vegetation types. Maxima of tree pollen relate to optimal (warm & humid) climatic events whereas dry episodes coincide with increased saltmarsh pollen and / or fungal bodies. Caspian influences are marked by influxes of brackish dinocysts and / or freshwater algae. The palynological records enable close correlation between cores in the modern delta and give a detailed history of evolution of the delta since the Late Pleistocene. The pollen data and results of shallow seismic indicate mainly aggradational and progradational deposition. The Pliocene delta was deposited c.500km to the south of the present day delta during a period of generally warm climate, indicated by increased representation of warm temperate tree pollen. The main types present are closely comparable with species found in Miocene and Early Pliocene macrofossil records from the Pannonian Basin in eastern Europe. Similar depositional trends are visible in both the modern and Pliocene Volga delta, and the palynological / palynofacies assemblages have proved useful in constructing facies and depositional models.  

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