A GEOPASS-NERC project on diatom deposition and sediment accumulation in Lake Baikal, Siberia

This new project is multidisciplinary, with physical and chemical palaeolimnological aspects mainly the responsibility of Swiss and Russian scientists, and the biological limnology and palaeolimnology components mainly undertaken by the British and Russian groups. The overall project aim is to improve palaeoclimate reconstructions using sedimentary diatoms by promoting better understanding of diatom ecology and sediment-forming processes. The initial work plan is divided into four main parts: To understand diatom phytoplankton ecology more fully, to assess taphonomic changes associated with the transformation of phytoplankton diatom communities into sediment assemblages, to demonstrate sediment core integrity and representativity and to calibrate modern diatom assemblages against contemporary climate records. The preliminary results from the interrelated studies of phytoplankton, sediment traps and sediment cores used in GEOPASS-NERC, demonstrate the complexity of links between the living and fossil systems. Furthermore, the nature of recent sedimentation in Lake Baikal is spatially variable and incompletely known. This poses a major challenge to palaeolimnological interpretation. Turbidite deposits and differential preservation of microfossils, combined with inadequate knowledge of the modern ecology of endemic diatoms, all conspire to obfuscate the sedimentary record of environmental change.

Interpreting the environmental record in the sediments of Blelham Tarn

Two aspects of the environmental record in the sediments of Blelham Tarn have been investigated: (1) the ecological history of the catchment, and lake-catchment relationships, by detailed analysis of the preserved pollen (as an indication of vegetation) and sediment composition with respect to a range of inorganic and organic geochemical variables and (2) a detailed investigation of the manner in which sediment is being formed today, including the way in which microfossils (pollen and diatoms) are being recruited and incorporated into sediments. When the record was examined by biological and geochemical analysis, together with radionuclide dating, of closely spaced samples, it was found that the changes of the last 30 yrs represented only the most recent episode in a long history of modification of the lake by man. To find an approach to this it is necessary to go back for at least 2500 yrs.

Variations in northeast Asian environments over the last 350,000 years reconstructed from pollen records from the northwest Pacific Ocean

EXTRACT (SEE PDF FOR FULL ABSTRACT): Recent analyses of terrestrial (pollen) and marine microfossils (foraminifera and radiolaria) in cores V28-204 and RC14-99 from the northwest Pacific Ocean extend the continuous, chronostratigraphically-controlled records of the regional vegetation of the Pacific coast of Japan and offshore marine environments through three full glacial cycles. The high-resolution pollen time series show systematic relationships between fluctuations in Japanese vegetation and global ice volume over the last 350 kyr. ... Comparison with solar insolation at 30°N and with an index of orbital parameters suggests that variation in northeast Asian summer monsoon intensity is related to orbital forcing.