A synthesis of post-glacial diatom records from Lake Baikal
A synthesis of post-glacial diatom records from Lake Baikal
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DOI：
10.1007/bf00684034
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发表时间：
1994-01-01
影响因子：
2.1
通讯作者：
Likoshway, Ye. V.
中科院分区：
文献类型：
--
作者：
Bradbury, J. Platt;Bezrukova, Ye. V.;Likoshway, Ye. V.
化石硅藻的生物地层学为西伯利亚东南部贝加尔湖提供了重要的年代学、古湖泊学和古气候资料。硅藻是沉积物中最具优势且保存最完好的微化石，其独特的组合和种类提供了整个盆地在千年至百年尺度上、在高沉积速率和低沉积速率环境下的核间相关性。独特物种的分布，曾经通过放射性碳测定年代，允许硅藻作为湖泊全新世历史的测年工具。Selenga三角洲脚下305号站点的硅藻、花粉和有机地球化学记录提供了从晚冰期（15ka）到全新世的古湖泊和古气候变化历史。在14ka之前，硅藻非常罕见，可能是因为冰川融水进入湖中的过度浑浊阻碍了生产力。在14ka至12ka之间，湖泊生产力增加，可能是因为强风促进了深层混合和营养物质的再生。花粉证据表明，此时贝加尔湖中部洼地以寒冷的灌木-草原景观为主。随着夏季日照的增加，针叶树取代了草原类群，但硅藻生产力在11至9 ka之间下降，这可能是由于猛烈的暴雨径流通过短而陡峭的排水通道进入湖泊导致夏季浑浊度增加。8千年后，较为干燥的大陆性气候盛行，贝加尔湖的现代硅藻植物群开始崭露头角。在院士岭，一个沉积速率缓慢的地点，10米岩心顶部的全新世硅藻组合在更深的层次上重新出现，这表明这些岩心至少记录了两个以前的间冰期（或间冰期？）。然而，在末次冰期之前发育的独特物种表明，贝加尔湖的营养循环动态和相关的区域气候环境并不完全类似于全新世的条件。在冰期，贝加尔湖深盆沉积物主要是由源头可能被冰川覆盖的大河迅速沉积而来的碎屑。然而，在海底院士岭（深度= 300 m），硅藻生物地层学的详细分析表明，diastems（持续时间较短的断裂）和（或）高度可变的积累速率使这些记录的古湖泊和古气候重建变得复杂。
The biostratigraphy of fossil diatoms contributes important chronologic, paleolimnologic, and paleoclimatic information from Lake Baikal in southeastern Siberia. Diatoms are the dominant and best preserved microfossils in the sediments, and distinctive assemblages and species provide inter-core correlations throughout the basin at millennial to centennial scales, in both high and low sedimentation-rate environments. Distributions of unique species, once dated by radiocarbon, allow diatoms to be used as dating tools for the Holocene history of the lake. Diatom, pollen, and organic geochemical records from site 305, at the foot of the Selenga Delta, provide a history of paleolimnologic and paleoclimatic changes from the late glacial (15 ka) through the Holocene. Before 14 ka diatoms were very rare, probably because excessive turbidity from glacial meltwater entering the lake impeded productivity. Between 14 and 12 ka, lake productivity increased, perhaps as strong winds promoted deep mixing and nutrient regeneration. Pollen evidence suggests a cold shrub - steppe landscape dominated the central Baikal depression at this time. As summer insolation increased, conifers replaced steppe taxa, but diatom productivity declined between 11 and 9 ka perhaps as a result of increased summer turbidity resulting from violent storm runoff entering the lake via short, steep drainages. After 8 ka, drier, but more continental climates prevailed, and the modern diatom flora of Lake Baikal came to prominence. On Academician Ridge, a site of slow sedimentation rates, Holocene diatom assemblages at the top of 10-m cores reappear at deeper levels suggesting that such cores record at least two previous interglacial (or interstadial?) periods. Nevertheless, distinctive species that developed prior to the last glacial period indicate that the dynamics of nutrient cycling in Baikal and the responsible regional climatic environments were not entirely analogous to Holocene conditions. During glacial periods, the deep basin sediments of Lake Baikal are dominated by rapidly deposited clastics entering from large rivers with possibly glaciated headwaters. On the sublacustrine Academician Ridge (depth = 300 m), however, detailed analysis of the diatom biostratigraphy indicates that diastems (hiatuses of minor duration) and (or) highly variable rates of accumulation complicate paleolimnologic and paleoclimatic reconstructions from these records.