Grain size, mineral and chemical compositions of modern deposits fron the northern Caspian Sea and the Volga River delta

Comprehensive investigations revealed that modern deposits in the northern Caspian Sea involve terrigenous sands and aleurites with admixture of detritus and intact bivalve shells, including coquina. Generally, these deposits overlay dark grayish viscous clays. Similar geological situation occurs in the Volga River delta; however, local deposits are much poorer in biogenic constituents. Illite prevails among clay minerals. In coarse aleurite fraction (0.100-0.050 mm) heavy transparent minerals are represented mostly by epidotes, while light minerals - mostly by quartz and feldspars. Sedimentary material in the Volga River delta is far from completely differentiated into fractions due to abundant terrigenous inflows. Comparatively better grading of sediments from the northern Caspian Sea is due to additional factors such as bottom currents and storms. When passing from the Volga River delta to the northern Caspian Sea, sediments are enriched in rare earth elements (except Eu), Ca, Au, Ni, Se, Ag, As, and Sr, but depleted in Na, Rb, Cs, K, Ba, Fe, Cr, Co, Sc, Br, Zr, ??, U, and Th. Concentrations of Zn remain almost unchanged. Sedimentation rates and types of recent deposits in the northern Caspian Sea are governed mainly by abundant runoff of the Volga River.

Chemistry and mineralogy of ODP Leg 124 sediment samples

From X-ray mineralogical studies and chemical analyses of the whole rocks and the fine fractions (<2 µm) of ten to fifteen samples at each site of ODP Leg 124, two major sources were identified in the sedimentary components of the Celebes and Sulu basins: (1) a terrestrial and continental contribution; (2) a volcanic influx that gives way to well-defined volcanic units or to a dilute contamination, consisting of coarse-grained minerals (Plagioclase, pyroxene, olivine, spinel) or a smectitic-rich fraction produced by the alteration of volcanic glasses and ashes. The continental signature increases the amount of quartz in the rocks and the phyllitic association is complex: micas, kaolinite, disordered interstratified clay-minerals. The chemical compositions of the bulk rocks and the fractions <2 µm are more potassic and aluminum-rich. The volcanic imprint depends on the grain-size and chemical properties of the components. Ca/Na contents highly variable compared to the K content of the bulk composition are due to the presence of coarse-grained volcanic Plagioclase. The fractions <2 µm are more magnesian than in the continental regime. The diagenesis is revealed by the crystallization of zeolites, the fixation of magnesium into the smectites that depletes the pore fluids in this element. Smectitization of the disordered interstratified clay minerals enriches the alkalinity of the pore fluids. Some deep formations of the Sulu Basin are affected by a thermal event, but no thermal event was recognized in the Celebes Basin.

(Table 1) Dissolved and particulate organic carbon, phosphorus, and nitrogen in waters of the Sea of Japan

Concentrations of dissolved and particulate organic carbon (DOC and POC, respectively), phosphorus (DP and PP, respectively) and particulate organic nitrogen (PON) were determined at Station VITYAZ6656 in the Sea of Japan in 12 sea water samples collected in June 1972 with a 200-liter sampling bottle. Mean weighted concentrations from the surface to 2000 m were: DOC - 1.58 mg/l, POC - 17.9 µg/l, DP - 13.9 µg/l, PP - 0.185 µg/l, PON - 2.7 µg/l, the ratios were DOC:DP=100:9 and POC:PON:PP=100:14:1. Relation between POC (µg/l)and the light attenuation index "e" (1/m) for the visible part of the spectrum is described by the equation POC = ca. 170e. The maximum of POC in the upper layer correlated with the maxima of phyto- and bacterioplankton and protozoa.

Grain size and chemical compositions of bottom sediments from the Amur Bay

Composition of clay minerals in the <0.001 mm size fraction from the uppermost layer of bottom sediments in the northern Amur Bay was determined by X-ray powder diffraction analysis, and enrichment of 33 elements in the <0.001 mm and <0.01 mm size fractions of surface sediments from a number of sites at the marginal filter of the Razdol'naya River were studied by ICP-MS. Fe, U, and chalcophile elements occur in the highest concentrations in sediments from all sampling sites within the filter. The bottom sediments are not enriched in trace, alkali, and alkaline earth elements. Maximum concentrations of chemical elements were found in deposits from the brackish part of the marginal filter, perhaps, because of formation of Fe and Mn (Al) hydroxides. Bottom sediments at the boundary between the brackish and marine parts of the filter contain the lowest concentrations of the examined elements.

Minerals of bulk samples and the fine-grained (<2-µm) fractions from DSDP Leg 67 Holes

Leg 67 sample sediments are mainly composed of biogenic carbonate and biogenic siliceous materials. Apart from calcite, crystallized minerals are scarce; however, they are better represented in sites near the continent and in all Quaternary sediments. These minerals are: quartz, feldspars, smectite, and, rarely, chlorite, dolomite, and zeolite.

(Table 1) Results of X-ray radiographic analyses of authigenic phosphorites from the Southwest Africa shelf

In the biologically productive area on the Southwest Africa shelf a current process of diagenetic phosphorite formation occurs. Remains of phytoplankton are the main source of phosphorus in host bottom sediments. Phosphorus concentrates in nodules due to its redistribution in bottom sediments and precipitation from interstitial waters. Accumulation of the phosphate nodules, as well as of scattered fish bone debris in sediments occurs at sudden change in hydrological conditions and removal of fine sediment fractions due to increased bottom currents or during transgressions.

Concentration of dissolved phosphates and total phosphorus in seawater near the Cape Utrish, Black Sea

Dynamics of growth of natural phytoplankton and bacterioplankton in deep seawater upwelled to the upper sea layer were studied. Seawater from the lower part of the aerobic zone of the Black Sea was shown to have high bio-productive potential and can be used as an environment for algae and bacteria cultivation.