785 resultados para Surface chemical composition
Resumo:
Paleotemperature curves were drawn from oxygen-isotope ratios in CaCO3 of planktonic foraminiferal tests and by the micropaleontological method using quantitative relationships of their species. Two series of curves yield similar results. These data confirm that isotope composition of oxygen reflects primarily temperature, and not isotope composition in ocean water. Temperature of the upper layer of ocean water increased from north to south both during the last two glaciations and in the interglacials. All three sediment cores collected from different latitudes show approximately the same amplitudes of fluctuation of mean annual temperature during times of their accumulation, as determined independently by different methods; these amplitudes are estimated as 5-7°C.
Resumo:
The monograph includes the study of chemical and mineral compositions of terrestrial and marine manganese ores, methods of their analysis, dependence of manganese crust geochemistry on tectonic position of their formation, problems of manganese genesis and sources of manganese in ocean ores in connection with geohistorical aspects of ocean formation and development. A hypothesis is offered that formation of giant manganese mineral basins on continental margins resulted from a large asteroid fall to the ocean.