玛珥湖与纹泥年代学
MAAR LAKE AND VARVE CHRONOLOGY
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摘要: 火山活动是影响全球变化的重要因素之一,玛珥湖和纹泥年代学是近年来古气候研究的新领域。玛珥湖由于其独特的封闭性及其物化条件,使之成为古环境变迁信息的理想载体。纹泥年代学是高分辨率研究过去全球变化的重要手段。玛珥湖的现存状态可以分为空型、湖型、沼泽型和干枯型。纹泥是某些玛珥湖中比较常见的一种沉积构造,它的形成需要一种精细的平衡。硅藻作为纹泥的一个重要组成部分,对光量、温度和各种无机盐反应敏锐,具有重要的古环境意义。能否制作完好的沉积物薄片是纹泥年代学成功与否的关键,本文对纹泥年代学的具体操作方法做了扼要介绍。中国有广泛的火山分布,其中不乏玛洱湖的存在,对之进行详细研究,不仅可以获得可与黄土、冰芯和深海岩芯相媲美的古气候序列,而且可以解决古气候学中某些难题。Abstract: Volcanic activity is one of the important factors that may affect global climate.Volcanic products can also provide records of palaeoenvironmental changes. Recently the study of maar lake and varve chronology is becoming a new field for palaeoclimate research.It provides high resolution records of palaeoenv0ironment with a time series on seasonal scale.Maar is a kind of collapse circular basin that is caused by phreatomagmatic explosion, and is cut into the pre-eruptive country rocks and surrounded by ring wall of pyroclastic material. Maar is small and has protective screen of wall. It receives sediments that are restricted within small area.Diatoms are common in maar lake. As a result of different adaptation to temperature and phototrophy, they have different shapes in different seasons. In the absence of diatom, we can distinguish varyes according to the sedimentary rhythm. These varyes recorded paleoclimate changes like tree rings. If we collaborate varve chronology with the absolute dating, we can establish high resolution time series of palaeoclimate,which may be valuable for studying climatic events influenced by the periodicity of sun spot and other short periodicity events such as El Nino.There are a lot of volcanoes in China. Among them, there are some maars. It is hoped that geological sequences from maars comparable with loess, ice core and deep-sea core will soon be available for palaeoclimatic analysis.
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Key words:
- maar lake /
- varve /
- diatom /
- varve chronology
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