Short-term fluctuations in vegetation and phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany)
Short-term fluctuations in vegetation and phytoplankton during the Middle Eocene greenhouse climate: a 640-kyr record from the Messel oil shale (Germany)
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DOI：
10.1007/s00531-010-0609-z
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发表时间：
2011-11
影响因子：
2.3
通讯作者：
O. Lenz;V. Wilde;W. Riegel
中科院分区：
文献类型：
--
作者：
O. Lenz;V. Wilde;W. Riegel
古近纪是地球上最近的温室期。特别是在古新世晚期和始新世早期，已经描述了几个叠加的短期高温事件，包括极端事件，如古新世-始新世热最大值。记录了与这些事件有关的海洋和陆地领域的主要动物群和植物群的更替。高分辨率孢粉分析中始新世早期玛珥湖沉积物在梅塞尔，达姆施塔特，德国附近，提供了一个深入了解顶极植被在中始新世温室气候的时间跨度没有显着的气候偏移的动态。数值技术，如去趋势对应分析和小波分析已被应用到识别周期性波动和长期趋势的植被通过一个时间间隔约640 kyr。根据花粉图的数值分带，可将植被的发育分为三个阶段。在整个这些阶段，顶极植被没有实质性的变化，在质量上的组成，但可能在结合在湖的水位下降明显较低的湿度条件的趋势可能会被确认。藻类种群从淡水甲藻cystMesselodinium thielepfeifferae的核心的最高部分的优势ofBotryococcus的转变被解释为响应内的酸度和营养物质的可用性变化的湖泊。花粉组合的时间序列分析表明，在米兰科维奇范围内的偏心率，结晶度和岁差的变化可以区分。此外，在子米兰科维奇范围内的波动表示。这表明，在稳定的沉积条件下，在中始新世的梅塞尔植物的变化是由轨道强迫。
The Palaeogene was the most recent greenhouse period on Earth. Especially for the Late Palaeocene and Early Eocene, several superimposed short-term hyperthermal events have been described, including extremes such as the Palaeocene–Eocene Thermal Maximum. Major faunal and floral turnovers in the marine and terrestrial realms were recorded in association with these events. High-resolution palynological analysis of the early Middle Eocene maar lake sediments at Messel, near Darmstadt, Germany, provides an insight into the dynamics of a climax vegetation during the Middle Eocene greenhouse climate in a time span without significant climatic excursions. Numerical techniques like detrended correspondence analysis and wavelet analysis have been applied to recognize cyclic fluctuations and long-term trends in the vegetation through a time interval of approximately 640 kyr. Based on the numerical zoning of the pollen diagram, three phases in the development of the vegetation may be distinguished. Throughout these phases, the climax vegetation did not change substantially in qualitative composition, but a trend towards noticeably less humid conditions probably in combination with a drop of the water level in the lake may be recognized. A shift in algal population from the freshwater dinoflagellate cystMesselodinium thielepfeifferaeto a dominance ofBotryococcusin the uppermost part of the core is interpreted as a response to changes in acidity and nutrient availability within the lake. Time series analyses of pollen assemblages show that variations in the Milankovitch range of eccentricity, obliquity and precession can be distinguished. In addition, fluctuations in the sub-Milankovitch range are indicated. This demonstrates that floral changes during steady depositional conditions in the Middle Eocene of Messel were controlled by orbital forcing.