Pollen counts from Kasten corer CON01-603-5 at CONTINENT Ridge.
Laboratory processing of concentrates was aimed at the removal of non-sporomorph organic matter by means of chemical treatment, micro-sieving and heavy liquid seperation. The optained concentrates were checked under the microscope and sample purity was estimated on the basis of particle counts. The results of AMS 14C dating show differences in the sedimentation rate among three sites of Lake Baikal.
At both sites, the lowest dry bulk density values (ca. 0.40 g cm−3) correspond to intervals with high diatom concentrations and high sediment accumulation rate. By contrast, the top and bottom of the sections analysed, rich in clay minerals, have high dry bulk density but low diatom concentration and sedimentation rate (Fig. 3).
Dissolution was high throughout the profile—in most cases, only 10–20% of the valves considered as pristine (Fig. 4). High relative percentages of A. baicalensis and of benthic Fragilaria (sensu lato) were positively correlated (r=0.29 and r=0.26, respectively) to samples with large proportions of pristine valves. There were no significant relationships between this index of dissolution and any of the other dominant taxa. Fragmentation of the valves was also high. On average only 45% of the total count was represented by whole valves (Fig. 4) and high percentages of non-fragmented valves were positively correlated with the percentages of pristine valves. The percentages of pristine valves showed high variation (20–70%) and by contrast with the dissolution index, they were significantly correlated with the variations in percentages of many dominant taxa.
The diatom succession at Academician Ridge is similar to the one from Continent Ridge and the two records, despite having very different sampling resolution, can be easily compared on the basis of their main floristic changes (Fig. 6). BVAR at Academician Ridge is about half that of Continent Ridge. There are also marked differences in the relative abundance of some taxa. At Academician Ridge, S. grandis and A. baicalensis are more abundant and S. formosus and C. sp. cf. operculata are less abundant than at Continent Ridge. The large peak in vegetative cells of A. skvortzowii found at Continent Ridge (DAZ 2) is absent at Academician Ridge, and is the most striking difference between the two records.