Late Quaternary paleohydrology in the North American Great Plains inferred from the geochemistry of endogenic carbonate and fossil ostracodes from Devils Lake, North Dakota, USA
Late Quaternary paleohydrology in the North American Great Plains inferred from the geochemistry of endogenic carbonate and fossil ostracodes from Devils Lake, North Dakota, USA
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DOI：
10.1016/0031-0182(96)00002-8
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发表时间：
1996-09
期刊：
影响因子：
--
通讯作者：
B. Haskell;D. Engstrom;S. Fritz
中科院分区：
文献类型：
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作者：
B. Haskell;D. Engstrom;S. Fritz
北达科他州魔鬼湖是一个封闭盆地湖泊，其中水化学对水文变化敏感，使其成为记录古气候条件的宝贵资源。岩心中的 Ostracode 微量元素和大量碳酸盐地球化学用于生成 12,000 年盐度波动记录。大量碳酸盐部分中 Sr、Ca 和 Ba 的相对含量可以在机械上与沉积物矿物学（方解石/霰石）和/或溶质化学的变化联系起来，而介形阀的元素地球化学反映了溶质化学。在来自魔鬼湖岩心的介形虫阀门中，相关的 Sr/Ca 最小值和 Mg/Ca 最大值可能是由于在含盐量较高的区间内多个矿物相沉淀过程中霰石介导的 Sr 化学反应。根据地球化学指标，魔鬼湖记录可分为四个水文时期： (a) 12.5−9 k.y.：低盐度； (b) 9.5−4.5 k.y.：波动的含盐条件，最大值约为 8 k.y.； (c) 4.5−3.5 k.y.：低盐度阶段，但可能不如 12.5−9 k.y. 时那么新鲜； (d) 3.5 k.y.-现在：盐相，尽管通常低于 9.5−4.5 k.y.然而，整个记录的特点是存在很大程度的变化，表明该地区缺乏长期的气候稳定性。
Devils Lake, North Dakota is a closed-basin lake in which water chemistry is responsive to hydrological changes, making it a valuable resource for documenting paleoclimate conditions. Ostracode trace-element and bulk-carbonate geochemistry in a core are used to generate a 12,000-year record of salinity fluctuations. The relative amounts of Sr, Ca and Ba in the bulk-carbonate fraction can be linked mechanistically to changes in sediment mineralogy (calcite/aragonite) and/or solute chemistry, whereas the elemental geochemistry of ostracode valves reflect solute chemistry. Associated minima in Sr/Ca, and maxima in Mg/Ca, in ostracode valves from the Devils Lake core may be due to aragonite mediation of Sr chemistry during the precipitation of multiple mineral phases during more saline intervals. The Devils Lake record can be divided into four hydrological periods on the basis of the geochemical proxies: (a) 12.5−9 k.y.: Low salinity; (b) 9.5−4.5 k.y.: Fluctuating, saline conditions with a maximum at about 8 k.y.; (c) 4.5−3.5 k.y.: Low salinity phase, but probably not as fresh as at 12.5−9 k.y.; (d) 3.5 k.y.-Present: Saline phase, although generally less so than 9.5−4.5 k.y. However, a large degree of variability characterizes the entire record, suggesting the absence of long-term climatic stability in this region.