Age model and chemistry of sediment core STK7 from Steisslinger See

Stable isotope records for carbon and oxygen in bulk carbonates, carbon in bulk organic matter, and for total and chromium-reducible sulfur in a lacustrine sediment core from Lake Steisslingen (Southwest Germany) show several distinct and abrupt shifts during the last 15,000 years. Variations in the isotopic composition of authigenic carbonates indicate two major phases in the lake history. In the pre-Holocene, the hydrological budget of the lake was apparently stable. Variations of delta18O values of authigenic carbonates were, therefore, dominantly controlled by temperature changes. A decrease in the delta18Ocarb values of about 2 per mil at the Allerød/Younger Dryas transition is interpreted as a drop in mean annual air temperatures of approximately 5°C. An abrupt temperature increase of a similar magnitude is inferred at the Younger Dryas/Preboreal boundary. Throughout most of the Holocene, the isotopic composition of authigenic carbonates was influenced by marked changes in the hydrological budget of the lake. A major positive excursion in the delta13Ccarb and delta18Ocarb values at the beginning of the Atlantic and a smaller one in the Preboreal were related to evaporation effects, which indicate that dry climatic conditions must have prevailed at that time. A simultaneous increase in delta13C values of bulk organic matter at the beginning of the Atlantic suggests a high level of productivity in the lake. As a consequence, aqueous sulfate became limited as indicated by variations in the delta34S values of total and chromium-reducible sedimentary sulfur. Therefore, we conclude that the beginning of the Atlantic was characterized not only by dry but also by warm climatic conditions, which triggered a higher productivity in the lake. In the Subatlantic sediments, large variations in carbon, oxygen, and sulfur isotope ratios were observed as a result of human activities, causing considerable perturbations in the biogeochemical element cycling of Lake Steisslingen. Results obtained by the study of the continuous 15 ka record of Lake Steisslingen document clearly that isotopic proxy data from lacustrine sediments can provide useful information on environmental and climatic changes of local, regional, and in the case of the Younger Dryas event, of even hemispherical significance.

采自德国西南部施泰斯林根湖（Lake Steisslingen）的湖相沉积物岩芯（lacustrine sediment core），其全岩碳酸盐（bulk carbonates）的碳、氧同位素组成、全岩有机质（bulk organic matter）的碳同位素组成，以及总硫与铬还原硫（chromium-reducible sulfur）的稳定同位素组成记录显示，过去15000年间存在多次显著且突变的同位素偏移。自生碳酸盐（authigenic carbonates）的同位素组成变化揭示了该湖泊演化历史中的两个主要阶段。全新世前（pre-Holocene）阶段，该湖泊的水文收支（hydrological budget）整体稳定，因此自生碳酸盐的δ¹⁸O值变化主要受温度变化调控。在阿勒罗德/新仙女木（Allerød/Younger Dryas）过渡期，自生碳酸盐的δ¹⁸Ocarb值下降约2‰，这被解释为年平均气温下降约5℃。在新仙女木/前博林（Younger Dryas/Preboreal）边界处，可推断出现了幅度相近的气温快速升高事件。全新世（Holocene）的绝大多数时段内，自生碳酸盐的同位素组成受湖泊水文收支的显著变化影响。大西洋期（Atlantic）初期，δ¹³Ccarb与δ¹⁸Ocarb值出现显著正偏；前博林期（Preboreal）则出现幅度较小的正偏，二者均与蒸发效应（evaporation effects）相关，表明当时气候以干旱为主。大西洋期初期，全岩有机质的δ¹³C值同步升高，表明当时湖泊生产力处于较高水平。随之而来的是水体硫酸盐（aqueous sulfate）供应受限，这一结论可通过总沉积硫与铬还原沉积硫的δ³⁴S值变化得到佐证。因此本研究认为，大西洋期初期兼具干旱与温暖的气候特征，这推动了湖泊生产力的提升。亚大西洋期（Subatlantic）的沉积物中，碳、氧、硫同位素比值出现大幅波动，这是人类活动导致施泰斯林根湖生物地球化学元素循环（biogeochemical element cycling）发生显著扰动的结果。本研究对施泰斯林根湖连续15000年沉积记录的分析结果清晰表明，湖相沉积物的同位素代用资料（isotopic proxy data）可为局地、区域乃至（如新仙女木事件这类）半球尺度的环境与气候变化提供有效参考信息。