PhD Defence ceremony Keith Richards
On Wednesday 16 May, Keith Richards will defend his PhD thesis
Oudezijds Voorburgwal 229 - 231 | 1012 EZ AmsterdamGo to detailpage
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Studies in Caspian palynology: six million years of vegetation, climate and sea level change
This thesis highlights some of the geological, geographical and climatic events in the depositional history of the Caspian Sea, from the latest Miocene to the present day. Just over 6 million years ago, the Caspian Sea was connected to the brackish-marine Paratethyan Sea during the ‘Pontian’ regional stage, before becoming an isolated lake basin during the Pliocene. These fluvio-lacustrine sediments are studied for their palynological content. A change from steppe to forest vegetation suggests climatic warming related to the ‘Mid Pliocene Warm Period’. A return to marine conditions during the ‘Akchagyl’ regional stage at the end of the Pliocene is shown by dinoflagellate cysts and foraminifera. Marine waters may have come from the Arctic Ocean. Brackish dinocysts in the early Pleistocene ‘Apsheron’ regional stage show similarity with the Black Sea region and Eastern Europe. Late Pleistocene sediments are studied from the Emba-Ural Delta region of Kazakhstan. Desert dunes are linked with the Atelian lowstand of the Caspian Sea during MIS (Marine Isotope Stage) 4. Lagoonal deposits contain pollen from thermophilous-hygrophilous trees of East Asian affinity during MIS 3. Palynological analyses from the Volga Delta recognise four phases of Holocene delta development. Incision of the delta occurred during the Derbent lowstand at the time of the ‘Medieval Warm Period’, followed by an expansion of aquatic vegetation equated with the ‘Little Ice Age’ highstand. The Caspian Sea that we see today is the result of a continuing process of basin isolation and periodic reconnection with the world’s oceans.