Conference:
IAS 28th Meeting of Sedimentology, Zaragoza, Spain, 5-8 July 2011.
Authors:
Elmira Aliyeva, Salomon B. Kroonenberg, Marc de Batist, Dadash Huseinov, Alya Baba-Zadeh, Robert Hoogendoorn, Jean-Pierre Suc, Lise de Mol, Nicola Kasimov, Mikhail Lychagin, Tine Missiaen.
Abstract:
The Caspian Sea was separated from the Paratethys Ocean at the end of Messinian because of the collision of the Afro-Arabian and European plates. An applied multi-component approach based on the integration of multiple geology and analytical tools – sedimentology, paleontology, sequence stratigraphy, biostratigraphy, chemostratigraphy, isotope and trace element geochemistry demonstrates a strong influence of climatically driven rapid fluctuations of the Caspian Sea level on stratigraphic architecture and faunal assemblages in the Plio-Holocene succession. The data have been obtained from the several sites – Late Pleistocene – Holocene delta of the Kura river in the South-West Caspian Sea, Lower-Middle Pleistocene outcrops in the Absheron peninsula (South Caspian basin), exposure of Pliocene sediments in the Kirmaki and Yasamal Valleys (South Caspian basin). Tens of shorterm climatic cycles in Lower Pliocene resulted in PalaeoCaspian sea level fluctuations affecting temporal facies distribution and shifts in the range of fluvial-lake environment. A proximal setting dominated in cool periods. A distal prodeltaic – lacustrine environment was established in warm humid stages. Several Lower-Middle Pleistocene full depositional cycles of a high order are clearly identified. Data on O, C isotope compositions, Ca/Mg and Sr/Ba ratios of ostracods shell carbonate testify to significant climatic and basin salinity changes throughout the Pleistocene accompanied by facies variability within shoreface -offshore environments. As a rule, decreasing temperature was followed by the sea level fall. The low stands are recorded in the coolest periods. In the Late Pleistocene-Holocene succession of the Kura river delta, several phases of delta retrogradation during the Caspian Sea highstands were interrupted by erosional phases during lowstands, recognizable in the seismic profiles as prominent reflectors. The first phase (24-25 14C kys BP by) is represented by coarse sands with numerous shell fragments encountered at the subCaspian depth of 34 m (falling stage). Overlying dark reddish-brown sandy shales (interval 30-34 m) deposited in the continental environment in the time interval between 18 and 23.7 14C kys BP (last glacial) correspond to the deep last Pleistocene Caspian low stand (- 102m). Subsequent gradual temperature increase was accompanied by the sea level rise recorded in core samples as grey shales with numerous molluscs and ostracodes. This succession is truncated by an erosional phase at the beginning of the Holocene recognisable in the core as peat deposits or shallow water grey sandy shales with sand laminas and shallow water ostracodes. The sea level was gradually falling from -92 m (12 14C kys BP) to -96.5 m (9,24 14C kys BP). Recovered palynomorphs display cool temperature and a peak in halophytes. These sediments are overlain by several metres of thick laminated clays and silts truncated by a prominent reflector at 1400 14C kys BP (last deep Holocene low stand at -48 m). Palynomorphs suggest that sedimentation took place in the cool environment.