Geophysical processes and biosphere: article

Аnnotation: Late Holocene sediments have been recovered in a core from the central part of the Chukchi Sea to reconstruct the conditions of their accumulation. The sediments consist mainly of terrigenous and just partly of biogenic material. Fine sand is dominated by up to 99.8 % light fraction minerals, whereas heavy minerals account for not more than 1.4 %. Results of magnetic susceptibility, related to sand and heavy mineral content, decrease from bottom to top of the core. The species composition of the palynospectra varies insignificantly over the core and, on the whole, reflects the modern vegetation of the coast of the Chukchi Sea. The increased number of cysts of dinoflagellates and other aquatic palynomorphs, as well as some increased content of coarse-grained material at the up-per part of the sediment core, is caused presumably by recent climate warming conditions. Two peaks of 137Cs activity at 7.5 and 1.5 cm core depths are related to radioactive fall-out, caused by the accidents at the Chernobyl nuclear power plant in 1986 and the Fukushima nuclear power plant in 2011. The resulting rates of sedimentation of 2.5 mm/yr to 3 mm/yr correspond well to rates of sedimentation, determined by 210Pb dating (2.0 mm/yr).