Oligocene records of the climate and sea level chances in the South-Caspian Basin: integration of lithofacies and diatom analyses
E.G. Aliyeva, N.T. Karimova, H.A. Allahverdiyeva
Azerbaijan National Academy of Sciences, Institute of Geology and Geophysics, H. Cavid ave., 119, Baku, AZ1143, Azerbaijan, E-mail: e_aliyeva@gia.ab.az; nayila_kerimova@mail.ru; hallahverdiyeva63@gmail.com
We integrated the lithostratigraphic, biostratigraphic
(diatom analysis) data from the well documented continuous Oligocene (Lower
Maykopian) succession cropping out in the Azerbaijan part of the South Caspian
basin, and correlated them with the oxygen isotopic composition in the Oligocene
benthic foraminifera shells, as well as the Global Ocean and the Eastern
Paratethys level fluctuation curves.
This article displays the variability of diatom algae
associations throughout Oligocene, and emphases on the link of these floral
complexes changes with the climatic variations and consequent sea level
fluctuations reflected in the corresponding depositional environmental changes.
Based on paleoenvironmental analysis of the diatom assemblages the bionomic
conditions’ variations in the Early Maykopian (Oligocene) basin were recorded.
Neritic and littoral species of diatoms are frequently observed in the studied
section.
The distribution of the thermophile and cryophile
diatom species throughout Oligocene succession enabled distinguishing of
warming and cooling stages in the Oligocene history of the Caspian segment of
the Eastern Paratethys, and correlate them with Maykopian Sea level
fluctuations. The predominance of the marine diatom forms in the basal and top
portions of the studied succession is well explained by the more warmer
climatic conditions established this time in the Oligocene basin.
The recorded facies heterogeneity throughout the
studied Oligocene succession is well linked to the climatically forced sea
level changes.
The article also provides the ground for correlation
of the Eastern Paratethys Maykopian Sea level with Global Ocean level curve.
Keywords: Lower Maykopian (Oligocene) sediments, facies variability, Maykopian Sea level change, diatom algae, cooling - warming climatic stages