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Agarkov Andrey Yurievich
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snic@sochi.com, aagarkov77@mail.ru
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04.00.00 Geological-mineralogical sciences
Description
The dynamics of changes in the species diversity of radiolarians during the last 150 million years with accuracy to one geological century was determined. The basic patterns of species and taxa of high rank change had been established for the boundary between Cretaceous and Paleogene. There were revealed topomorphic features of bipolar species, which have succeeded from the Cretaceous into the Paleogene and became ancestors of Cenozoic radiolarian fauna. Changes in the species number in the boundary between Cretaceous and Paleogene periods, and also significant variations in the species diversity in Paleocene and Eocene are connected to a combination of a number of factors. The most important of those factors are geological processes, causing extensive transgressions and regressions, climate variability, the overall evolution direction of the Earth biota and competition for important chemical components for the Radiolaria’s livelihood. The emergence of powerful tropical forests on the land with their huge bio-production and bio-chemical erosion is connected to late Cretaceous era. This resulted increasing of the dissolved material proceeding into the sedimentation pool, what is confirmed by classical bauxites emergence. Because aluminium oxide and silicon oxide are geochemically connected, we can state as well about increasing of dissolved silica flow initiated development of Diatoms, which became competitors to Radiolaria in their battle for silica. The last ones are lost this battle, what caused the species decreasing. That was not a catastrophic event with immediate extinction, but a long process
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