Ages and sedimentation rates of bottom sediments from the south arid zone of the Pacific Ocean

Radiocarbon datings are used to calculate mean sedimentation rates of metalliferous sediments in the southern arid zone of the Pacific Ocean adjoining the axis of the East Pacific rise (20°S). Owing to low sedimentation rates and intense mixing, only averaged figures could be obtained for ages less than 16 ky. Sedimentation rate varies from 0.3 to about 1 cm/1000 years in the surface layer and is several times higher in the time interval from 20 ky to 45 ky ago. Formulas for calculating mean sedimentation rates with allowance for benthic mixing are presented.

Composition of bottom sediments from Mediterranean anoxis basins

Biomass and size structure of planktic infusoria communities were investigated in March 1987 at nine stations on a 370 mile transect across the coastal upwelling zone, the California current, and subtropical waters. Infusoria compose up to 71-92% of total biomass of heterotrophic micro- and nannoplankton; their biomass was 0.6-2.0 g/m**2 in the 0-200 m layer. Distinctive characteristics of taxonomic and size structures were of great diversity of microplanktic Stormbilidiwn forms, comparatively low abundance of tintinnids, and high abundance of nannoplanktic infusoria that accounted for 26-54% of biomass.