The periodic pattern of diatom sedimentation and geochemistry of diatom oozes in Lake Baikal

The Upper Pleistocene paleoclimatic records according to data of deep-water drilling in the Black Sea and Lake Baikal have been correlated. It has bee n shown that in both basins the two last interglacials were characterized b y intense diatom sedimentation. It is stated that the appearance of diatom oozes in the sediments is related to an increased inflow of dissolved silic a and nutrient salts. In oceans, this occurred during a rise of internal wa ter, and on continents it was caused by surface runoff in the epochs of int ense chemical weathering. The association of biogenic silica with uranium a nd organic matter (mainly humic acids) occurs not in Lake Baikal only but i s also characteristic of upwelling zones, where sedimentation of humic acid s and uranium is believed to occur at the water-bottom boundary. It has bee n found that the Baikal diatom sediments, already enriched in uranium in th e superficial layer, further accumulate it immediately beneath the redox bo undary. It has been demonstrated that the distribution of "clastophilic" el ements in the column of the Upper Pleistocene Baikal sediments is a mirror image of distribution of biogenic silica as a thinner. Each event recognize d in the oceanic paleoclimatic record in this time range is clearly pronoun ced in the sediment columns of the Akademichesky Ridge in Lake Baikal.