72 documents found in 239ms
# 1
De Batist, M. • Canals, M. • Sherstyankin, P. • Alekseev, S. • INTAS Project 99-1669 Team
Abstract: In 1999 it was decided to create an international team of specialists and combine efforts and expertise to produce a new, more accurate bathymetric map of Lake Baikal. The aim was to re-compile the original sounding data that were used for the 1992 maps, to digitise them, to correct them using up-to-date, calibrated acoustic velocity information, to integrate them with as much as possible of the more recently acquired sounding data, and to produce a new, computer-generated, computer version of the Lake Baikal bathymetry map based on ALL available sounding data.
# 2
Förster, A. • Hötzl, H. • Rettenmaier, D. • Kück, J.
Abstract: Several geophysical logs were obtained in 2002 in the AIG10 borehole. One set of logs (FMI, UBI, and DSI) were measured by Schlumberger in the deep, open-hole part of the borehole (Daniel et al., 2004; Prioul et. al., 2004). GFZ and ICDP OSG performed two logging campaigns with GFZ standard logging tools (Mud Parameter, SGR, GR-BCS-DIL and MSFL). The first campaign covered the section to a depth of 708 m (depth of casing), the second campaign covers the entire borehole to 1001 m (total depth). In May 2003, a third campaign was conducted by GFZ and IPGP, which included the measurement of a temperature log with GFZ's Distributed Optical Fibre Temperature Sensing (DTS) system.
# 3
Martin, Patrick • Boes, Xavier • Goddeeris, Boudewijn • Fagel, Natalie
Abstract: The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).
# 4
Martin, Patrick • Boes, Xavier • Goddeeris, Boudewijn • Fagel, Natalie
Abstract: The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).
# 5
Martin, Patrick • Boes, Xavier • Goddeeris, Boudewijn • Fagel, Natalie
Abstract: The vertical distribution of organisms in the sediment indicates that animals can be present as deep as 15 cm although at very low abundance at such depths (Fig. 4, Fig. 5 and Fig. 6). Oligochaetes and nematods are the only groups able to deeply penetrate into the sediment at significant densities (Fig. 4) in contrast to all other groups, which stay closer to the sediment surface. Maximal densities however seem to shift to the sediment surface with increasing bathymetric depth, as suggested in Fig. 5 and Fig. 6, so that all animal groups are more concentrated near the surface in the deepest parts of Lake Baikal. In such case, the depth of sediment mixing due to bioturbation appears to decrease with increasing bathymetric depth (Fig. 2b).
# 6
Martin, Patrick • Boes, Xavier • Goddeeris, Boudewijn • Fagel, Natalie
Abstract: In all abyssal stations, densities are never over an average of c. 3100 individuals m−2 (Fig. 3, Table 1). In contrast, the shallow station (CON01-427, Posolskoe Bank) harbours the highest observed densities (oligochaetes reach densities as high as 13573 individuals m−2 on average). Gammarids are present in this latter station at 128 m deep, while they are absent from all deep stations. The presence of some groups is anecdotal, such as Hydrachnidia (one specimen in a core at 388 m and two specimens in a core at 625 m) and chironomid larvae (two larvae in a core at 625 m). Interestingly, the two deepest Vydrino cores (CON01-105-7, 600 m, and CON01-106-3, 700 m) are virtually free from animals, suggesting that these stations are perhaps the best choice for the study of stratigraphy and climate proxies.
# 7
Mackay, Anson • Ryves, D. • Battarbee, Rick • Flower, Roger • Jewson, David • (et. al.)
Abstract: Diatom-inferred snow depth reconstructions for BAIK38 using uncorrected taxa (Fig. 5a–c) show similar trends throughout the study period, with all or only five taxa in the model; snow depth levels are marginally higher in zone 2 in comparison to zones 1 and 3. However, error values are large in comparison to the changes observed. The snow depth reconstruction using corrected diatom abundances (Fig. 5d) shows a somewhat different response. Low values characterise the period coincident with the MWP (between c. 880 AD and c. 1180 AD), which increase into the LIA, reaching peak depths between 1500 and 1775 AD. After then, snow depth values decline to their lowest values in this study by c. 1900 AD. In recent decades, snow depth values appear to increase slightly again up to the top of the core dated at 1994.
# 8
Mackay, Anson • Ryves, D. • Battarbee, Rick • Flower, Roger • Jewson, David • (et. al.)
Abstract: Preservation differences can be used as correction factors to recalculate the relative abundances of each of the five dominant plankton taxa in BAIK38 and are depicted in Fig. 4. The resulting profile shows that Synedra acus is now the dominant taxa in zone 1 of the core, with other taxa being present at abundances generally less than 10%. At the zone 1/2 boundary, S. acus declines and is replaced by Cyclotella minuta and, to a lesser extent, Aulacoseira skvortzowii and Aulacoseira baicalensis. This profile is different from the relative abundance profile in Fig. 3, as S. acus values decline to very low values by c. 1400 AD, and C. minuta increases to peak values between c. 1525 and 1650 AD. Furthermore, the profile indicates that A. baicalensis remains common throughout this zone. Towards the zone 2/3 boundary, taxa more characteristic of warmer waters increase earlier than previously suggested at c. 1750 AD.
# 9
Mackay, Anson • Ryves, D. • Battarbee, Rick • Flower, Roger • Jewson, David • (et. al.)
Abstract: Fig. 3 is the diatom stratigraphy of dominant phytoplankton taxa for BAIK38 expressed as relative percentages, plotted against the age scale. Zone 1 (c. 880 AD–c. 1180 AD) is dominated throughout by the autumnal blooming species Cyclotella minuta, while Aulacoseira baicalensis and Synedra acus (both of which bloom in spring) are also present in lower but similar proportions (c. 15%). Zone 2 (c. 1180 AD–1840 AD) is characterised by an increase in C. minuta values in excess of 80% relative abundance, which are sustained virtually throughout the zone. During this time, other taxa are present at only very low abundances, while some (e.g., Stephanodiscus meyerii and S. acus) are frequently absent. Zone 3 (c. 1840 AD–1994 AD) is characterised firstly by a decline in relative abundance of C. minuta to its lowest levels in the profile, up until c. 1950 AD. This decline is accompanied by concomitant increases in A. baicalensis and, to a lesser extent, Aulacoseira skvortzowii and S. meyerii.
# 10
Mackay, Anson • Ryves, D. • Battarbee, Rick • Flower, Roger • Jewson, David • (et. al.)
Abstract: Samples were routinely analysed for wet density (WD), percentage dry weight (%DW) at 105 °C, and loss-on-ignition analysis (LOI) at 550 °C, and data used to calculate diatom accumulation rates (DAR) in the sediment core. LOI is an approximation of organic content in sediment cores (Bengtsson and Enell, 1986). Each sample was prepared for diatom analysis using the procedure outlined in Mackay et al. (1998), minimizing additional dissolution of valves by omitting chemical pretreatments during preparation. Divinylbenzene microspheres (mean diameter 6.4 μm) were added to enable diatom concentrations and accumulation rates to be calculated (Battarbee and Kneen, 1982). Suspensions were settled on glass coverslips and permanent slides made using Naphrax slide mountant (refractive index 1.73). Diatoms were counted using oil immersion phase contrast light microscopy at ×1000 magnification.
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