Oxygen isotope analysis of diatom silica and authigenic calcite from Lake Pinarbasi, Turkey
Oxygen isotope analysis of diatom silica and authigenic calcite from Lake Pinarbasi, Turkey
复制标题
土耳其皮纳尔巴西湖硅藻二氧化硅和自生方解石的氧同位素分析
DOI：
--
复制
发表时间：
2001
期刊：
影响因子：
--
通讯作者：
J. Reed
中科院分区：
文献类型：
--
作者：
M. Leng;Philip Barnker;P. Greenwood;N. Roberts;J. Reed
硅藻二氧化硅的18 O/16 O比值越来越受到关注，特别是对于不存在碳酸盐的湖泊。在这里，我们比较保存在硅藻二氧化硅和自生方解石从一个开放的，春天喂，淡水湖从土耳其的核心，跨越海洋氧同位素阶段3的18 O/16 O比。两套同位素数据显示出截然不同的趋势，尽管它们的相互依赖的水18 O/16 O比值和湖水温度。这种差异最可能的解释是安纳托利亚高原强烈的大陆性气候所介导的生物生产力的季节性差异。硅藻二氧化硅和自生方解石是在一年中的不同时间从湖水中的溶质中沉淀出来的。硅藻的生产力遵循一个明确的季节性周期，首先是最重要的是在春季，然后是秋季。方解石的沉淀遵循所有形式的光合生物的生产力，消耗二氧化碳，但在大多数湖泊中，这发生在夏季。δ 18 Ocalcite曲线显示夏季平均温度最高值约为100 ℃。30-35和CA。58 ka BP，而干预数据代表了一段相对凉爽的夏季。硅藻δ 18 O曲线呈双极型（15-20 ‰和29-33‰），表明硅藻的氧组成至少有两个离散的来源或过程，但可能涉及稀释机制，使同位素值发生偏移。最有可能的枯竭水源是春季解冻时进入湖中的雪。我们推断，许多自生的方解石曲线，从地区明显的季节性气候可能会暂时限制在夏季的几个月，硅藻二氧化硅季节性特定的水同位素组成提供了补充数据，而不是替代分析的基础上碳酸盐。
There is increasing interest in the 18O/16O ratio of diatom silica, particularly for lakes where carbonates are absent. Here we compare the 18O/16O ratios preserved in diatom silica and authigenic calcite from an open, spring-fed, freshwater lake core from Turkey which spans marine oxygen isotope stage 3. The two sets of isotope data show contrasting trends in spite of their mutual dependence on the water 18O/16O ratio and lake-water temperature. The most likely explanation for this divergence is difference in seasonality of biological productivity mediated by the strongly continental climate of the Anatolian plateau. Diatom silica and authigenic calcite are precipitated from solutes in the lake-water at different times of the year. Diatom productivity follows a well-defined seasonal cycle, peaking first and most importantly in the spring and then in the autumn. The precipitation of calcite follows productivity by all forms of photosynthetic organisms that deplete CO2 but in most lakes this occurs during the summer months. The δ18Ocalcite curve shows mean summer temperature maxima at ca. 30–35 and ca. 58 ka BP while the intervening data represent a period of relatively cool summers. The δ18Odiatom curve shows bipolar results (15–20 and 29–33‰), which suggests that at least two discrete sources or processes contributed to the oxygen composition of the diatoms but probably involved a dilution mechanism to shift the isotopic values. The most likely source of depleted water is from snow entering the lake during the spring thaw. We infer that many authigenic calcite curves from regions with markedly seasonal climates may be temporally limited to a few summer months and that diatom silica provides complementary data on seasonally-specific water isotopic composition rather than a substitute for analyses based on carbonate.