Foraminiferal and palynological organic matter records of the Upper Badenian (Middle Miocene) deposits at Anadoly (marginal part of the Ukrainian Carpathian Foredeep Basin).

Abstract

The Badenian section of Anadoly near Kamyanets Podilskyy (Ukrainian Carpathian Foredeep Basin) consists of the Tyras Fm. (gypsum and Ratyn Limestone) and the Ternopil Mb. of the Kosiv Fm. The latter are 5.3 m thick and are composed of dark grey mudstones with limestone intercalations. This study indicates the occurrence of over 54 species of benthic foraminifers and 10 species of planktonics. Benthic foraminifera are represented mainly by calcareous forms; agglutinated tests are very rare. Planktonic foraminifera appear in the upper part of the succession studied. Five benthic foraminiferal assemblages are recognized: A (Elphidium/Lobatula/Astrononion) B (Hauerinidae), C (Cibicidoides/Lobatula), D (Porosononion) and E (Uvigerina/Bulimina). The foraminiferal record indicates deposition in a shallow subtidal environment (20 m depth) of normal marine salinity and temperate waters followed by gradual deepening of the basin to >50 m. Analysis of foraminiferal assemblages indicates that bottom waters were highly oxygenated during deposition of the lower and middle parts of the Anadoly sequence. During deposition of the upper part of the sequence the oxygenation of bottom water gradually decreased, as expressed by a large decrease in the proportion of oxic species and an increase in dysoxic ones. The same set of samples yielded low amounts of palynological organic matter represented by dominant black opaque phytoclasts; bisaccate pollen grains and dinoflagellate cysts are rare. Taxonomically impoverished assemblages of the latter consist of dominant Polysphaeridium and Cleistosphaeridium placacanthum associated with Lingulodinium machaerophorum and a few other taxa. The taxonomically richest assemblage was found in the topmost sample. These changes were interpreted as indicative for increased salinity in the surface water layer, with its maximum in the middle part of the section; the assemblage from the topmost part is characteristic for normal marine salinity.