Benthic and Plankton Foraminifers in Hydrothermally Active Zones of the Mid-Atlantic Ridge (MAR)

Comparison of benthic foraminiferal assemblages from the core obtained within the Peterburgskoe ore field (Mid-Atlantic Ridge) and from the core taken five kilometers away from the ore field revealed evident differences in their composition, in the appearance of their shells, and also in the benthic–plankton species ratio. It was noted that the foraminiferal assemblage from the ore-bearing sediments of the Petersburg field was characterized by a higher relative content of benthic species and a large number of chemically altered and broken shells. The first occurrence of the species Osangularia umbonifera, which is able to exist in lowoxygen and CaCO₃-undersaturated bottom waters at the boundary of biogenic sediments surrounding the ore field and in the ore-bearing sediments, was established. In the core section sampled beyond the ore field, the composition of foraminiferal assemblages differs insignificantly from typical oceanic ones.     

The Southern Baltic Seas in the Paleogene according to the study of the foraminifera

The changes in the paleocomplexes of the foraminifera, the remains of other organisms, and the lithological composition of the Paleogene deposits in the Kaliningrad region made it possible to reconstruct the sedimentation conditions during the Paleogene.     

Deep-Water Circulation in the Hunter Channel (Southwest Atlantic) in the Late Pleistocene and Holocene Based on Benthic Foraminifera

Oceanology - Based on benthic foraminifera from three sediment cores, the deep-water circulation near the Hunter Channel (Southwest Atlantic) in the Late Pleistocene and Holocene has been...     

Water masses of the northern part of the Iceland Basin in the late Pleistocene

A core of bottom sediments AMK-4438 with a length of 320 cm was taken in the North-Eastern part of the Iceland Basin from the depth of 2240 m. The continuous sampling (every 2 cm) made it possible to study the core using the principle of high-resolving paleoceanology. For the stratigraphic partition of the core, we applied the paleotemperature analysis by planktonic foraminifera and carbonate analysis; the distribution of the iceberg rafted debris (IRD) was studied. As a result, nine isotopic stages were distinguished. The change in the complexes of benthic foraminifera indicates that the present-day deepwater circulation in the North-Eastern part of the Iceland Basin had no analogs in earlier glacial periods, including the MIS 5 age. During almost 300 ka, there were relatively warm, rich in nutrients, and poor in oxygen water masses. The formation of the modern Northern-Eastern deep water in the Iceland Basin began in the Bolling-Allerod 14 ka B.P.     

Productivity of the benguella upwelling in the pleistocene: Evidence from benthic foraminifers

The taxonomic composition of the benthic foraminifers studied in 36 samples of Pleistocene sediments from DSDP Hole 362 drilled in Leg 40 of the D/V Glomar Challenger made it possible to divide the section into the lower and upper Pleistocene units. The variations in the relative proportions of the planktonic and benthic foraminifers and the abundance, diversity, and taxonomic composition of their benthic taxa imply that the Benguella Current in the Walvis Ridge area was located in the early Pleistocene westward of its present-day position, and the upwelling was more intense and its productivity was higher as compared with these parameters in the late Pleistocene. At the onset of the late Pleistocene, the Benguella Current occupied its present-day position with the intermediate waters ascending to the surface, which resulted in the decline of the upwelling’s productivity.     

Paleogeography of the Norwegian-Greenland and Northwestern European Sea Basins in the Paleogene

Published and original data on the lithology and fauna (mainly foraminifers) of the Paleogene Norwegian-Greenland and Northwestern European Sea Basins are generalized in this article. Their paleogeographic evolution and the character of development of connections with the North Atlantic, Mesotetis, and the Arctic Ocean are established from the moment of generation to their disappearance. It is shown that the paleogeographic conditions of the studied sedimentation basins depend to a great extent on the tectonic movements of lithospheric plates. Iceland Plume volcanism exerted a considerable influence on the paleoenvironment and sedimentogenesis. The paleotectonic and climatic conditions of sedimentation are reconstructed. The occurrence of bauxite-bearing continental residual soil and other data point to a tropical, humid climate in the Early Paleogene, which changed into a moderate humid climate by the end of the Late Paleogene. Terrigenous sediments, including oil-and-gas bearing ones, were formed in the sea basins; they contain products of eroded residual soil, placers of accessory minerals, pyroclastics of volcanoes of the Iceland Plume, and zeolite-bearing, amber-bearing, phosphorite-bearing, and glauconitic horizons that have practical interest.     

Paleogeography of the Southern Baltic Region in the late Mesozoic: Implications of foraminifers

Foraminifers from Middle-Upper Jurassic and Upper Cretaceous sediments of the Kaliningrad basin located in the southwestern part of the East European platform are studied. During the greater part of the Late Mesozoic, the study region represented a northern margin of a spacious epicontinental sea in the Boreal zoogeographic realm. The analyzed composition and quantitative distribution of foraminifers, ratio between planktonic and benthic species, ornamentation degree of tests, and their preservation are used to reconstruct paleogeography and history of eustatic sea-level changes. The upper Callovian through Upper Jurassic zonation based on distribution of Epistomina species is proposed. Defined foraminiferal assemblages are correlated with coeval assemblages from the East to West European platforms and North Atlantic     

Upper quaternary biostratigraphy and formation environments of the southwestern Atlantic Core ACB-17-1447 inferred from micropaleontological data

The foraminiferal (planktonic and benthic) and nannofosssil assemblages have been analyzed in the sediments of Core ACB-17-1447 taken from the South America continental slope north of the Rio Grande Rise piedmont during Cruise 17 of the R/V Akademik Sergey Vavilov. The core section is largely composed of carbonate and marly hemipelagic mud. The Quaternary age of the host sediments is evident from the occurrence of the planktonic foraminiferal index species Globorotalia truncatulinoides. Based on the nannofossil assemblages, the core sediments are attributed to the upper Pleistocene-Holocene. They contain abundant reworked Pliocene, Miocene, and Paleogene taxa transported from the slopes of the underwater Rio Grande Rise. The paleotemperature analysis of the planktonic foraminifers provided data for constructing the temperature curve that demonstrates two warm peaks. During the first warm period (Interval of 7–9 cm), the surface water temperature was as high as 26°C (Holocene optimum), which exceeds by 3–4°C its presentday values and implies the more intense warm Brazil Current. The earlier warm peak with temperatures up to 24°C recorded in the upper Pleistocene sediments (Interval of 69–71 cm) most likely reflects the 3rd oxygenisotope stage (MIS 3), which corresponds to the interstadial phase of the last glaciation (30–40 ka ago). Based on the abundances, taxonomic diversity, and proportions of the characteristic species of benthic foraminifers, the Core ASV-17-1447 section is divided into six intervals correlated with the marine isotopic stages defined by both the planktonic foraminifers and climatic changes evident from the variations in the bottom water circulation along the southwestern slope of the Brazilian Basin during the Late Quaternary.