Место издания:Berichte des Institutes für Erdwissenschaften Karl-Franzens-Universität Graz Instute of Earth Sciences, Department of Geology and Palaeontology, University of Graz, Heinrichstrasse 26
Первая страница:385
Последняя страница:385
Аннотация:The assemblages of planktonic foraminifers and radiolarians are investigated from the same samples
that have been collected from Cenomanian-Maastrichtian sequences of East-European platform,
Caucasus, as well as the Cenomanian-Campanian of Crimea.
The Cenomanian interval was a time of polytaxic development due to warm greenhouse and correlated
with sea level rise. The appearance of abundant multichamber cyrtoidal pseudomacrocephalic, as well
as cryptocephalic and cryptothoracic forms in the Cenomanian is apparently reflected a changing of
hydrological conditions and it was probably caused by the active adaptation. The extinction of singlekeeled
rotaliporides in foraminiferal community, reduction of a morphological variety, violation of the
correct system of porosity in radiolarians coincides with the Cenomanian–Turonian boundary event.
The Turonian-Coniacian diversification of all foraminiferal and radiolarian groups probably is related
to a sea-level highstand and hot greenhouse climatic environment. The Tethyan species reached
Moscow Region of the Russian Plate. Acme of double-keeled and single-keeled marginotruncanids,
concavatotruncanids and their diversification in Turonian-Santonian reflects more stable conditions in
a more oligotrophic regime. The replacement of very specialized marginotruncanids/
concavatotruncanids into marginotruncanids by globotruncanids at the Santonian-Campanian
boundary probably are related to penetrating of cold water to south up to North Caucasus and Crimea
and reflected a cooling episode. The occurrence of temperate and high paleolatitude family
Prunobrachidae Pessagno in the North Caucasus locations is also indicative of cool greenhouse
environments.
The invasion of cold water from Arctic Region through the Russian Plate (Baraboshkin et al., 2003;
Naidin et al., 2007; Blakey, 2012; Pugh et al., 2014) to South is confirmed by finding of Genus
Prunobrachium in North Caucasus and Crimea Location. Latest Cretaceous family Prunobrachidae
Pessagno occurs mostly in temperate and high paleolatitudes. Mass abundance of Prunobrachidae is
indicative of cold water environments, which were characterized for Polar Urals, Russian Plate,
Siberia, Russian Far East, South PaleoPacific (Tasman Sea) and New Zealand. Analysis of
Prunobrachidae paleogeography during Late Santonian-Campanian shows bipolar distribution in
temperate and high paleolatitudes. The distribution areas are almost symmetrical relative to theequator: 35º-62º N in the Northern Hemisphere and 50º-52º S in the South. It is very important to use representatives of family Prunobrachidae in the study of paleogeography and ecostratigraphy, as well as stratigraphic correlation of Tethyan and Boreal sequences of the Upper Cretaceous.The finding of calcareous dinocyst Pithonella globosa Futterer widespread in an interval Middle Maastrichtian–early Danian together with Orbiculiforma australis Pessagno, O. renillaeformis ampbellet Clark, Tholodiscus densus (Kozlova), allows to indicate rather warm episode during accumulation of the Late Maastrichtian siliceous clays.
This research was supported by the Russian Foundation for Basic Research: 13-05-00447, 15-05-04700, 15-05-04099 and IGCP-609 Project.