Characteristic Property of the Formation of Authigenic Minerals in Bottom Sediments of the South Caspian Basin under Hydrogen Sulfide Contamination Conditions

Oceanology - The paper presents the results of lithological, mineralogical, and geochemical studies of bottom sediments in the central part of the South Caspian Basin. A complex of analytical...     

Distribution of some rare and trace elements in modern bottom sediments of the Caspian Sea

The features of the distribution of some rare and trace elements in modern bottom sediments of the Caspian Sea have been studied from samples collected during cruises 35, 39, and 41 of the R/V Rift and the cruise of the R/V Nikifor Shurekov in 2013. It was established that bottom sediments in different areas of the Caspian Sea vary to some degree in the contents of Zr, Hf, Th, V, Cr, Co, Ni, Cu, Sr, and Ba in comparison to suspended matter discharged by the Volga River and rivers originating in the Caucasus. As follows from the results of a comparison of the geochemical features of modern bottom sediments of the Volga River delta and different sedimentary subsystems of the Caspian Sea with the chemical composition of Middle Archean granitoids and Paleozoic and Mesozoic–Cenozoic basalts, which are regarded as geochemical images of such provenance areas as the basement of East European Platform, Urals, and Caucasus, none of these regions is considered the dominant provenance area for all sedimentary subsystems of the Caspian Sea region. Here, the revealed similarity between modern bottom sediments of the northern, central and southern Caspian Sea regions, the Volga River delta, and Post-Archean average Australian shale (PAAS) in some parameters, including REE spectra, assumes that the Volga River discharge plays a dominant role in the formation of the geochemical image of Caspian Sea subsystems. The role of clastics, including the fine-grained fraction, which is supplied to the Caspian Sea from the Caucasus region and Elburz Mountains, is insignificant already in the coastal area, which is determined both by influence of the marginal filter (MF) and large-scale cholestatic current circulation.     

Isotopic Composition of Nd,Pb, and Sr in Modern Bottom Sediments of the Barents Sea

Doklady Earth Sciences - The isotopic characteristics (εNd, 207Pb/206Pb, and 87Sr/86Sr) of the modern bottom sediments sampled in the Barents Sea during the 67th voyage of the R/V Akademik...     

Lithological and Biogeochemical Investigations of the North Atlantic Sediment System (Data from the 49th Cruise of the R/V Akademik Ioffe)

Oceanology - Marine sediments and samples of suspended particulate matter from the North Atlantic were studied. It is shown that modern sedimentation in this area is controlled mainly by the...     

First find of kutnohorite in modern sediments of the South Caspian basin

High-manganese kutnohorite was found in the surface layer of bottom sediments of the South Caspian basin by the method of X-ray diffraction for the first time. Bottom sediments were collected by a multicorer during the 39th voyage of R/V Rift in 2012. Study of the samples by a complex of methods (X-ray diffraction, scanning electron microscopy, atomic absorption, and analysis of the carbon isotope composition) allowed us to attribute kutnohorite to autigenic minerals of the early stage of diagenesis.     

Composition of fragmental minerals of the surface layer of bottom sediments in the Caspian Sea

The mineral composition of heavy and light subfractions of the modern bottom sediments of the Caspian Sea is studied. The concentration of the minerals in the Caspian Sea made it possible to identify nine terrigeneous mineralogical provinces in its area. Based on the mineral composition of the heavy subfraction of the bottom sediments, the main sources of the fragmentary material supply are established. The distribution of the terrigeneous minerals over the bottom area in the modern bottom sediments of the Caspian Sea depends on the sources of the fragmentary material; the stability and flotation properties of minerals; the morphology of the bottom; and the hydrodynamic conditions.     

Mineral composition of sedimentary matter in the Caspian Sea

Data on the mineral composition of sedimentary matter and its fluxes in the sediment system of the Caspian Sea are presented. River runoff, aerosols, particulate matter from sediment traps, and the upper layer (0–1 cm) of bottom sediments are considered. The contents of detrital minerals (quartz, albite, and K-feldspar), clay minerals (illite, chlorite, and kaolinite), and carbonates (calcite, Mg-calcite, dolomite, aragonite, and rhodochrosite) are determined. Gypsum was found in bottom sediments but is absent in the other object of the sediment system.