Investigating the hydrological significance of stalagmite geochemistry (Mg, Sr) using Sr isotope and particulate element records across the Late Glacial-to-Holocene transition
Investigating the hydrological significance of stalagmite geochemistry (Mg, Sr) using Sr isotope and particulate element records across the Late Glacial-to-Holocene transition
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DOI：
10.1016/j.gca.2016.10.024
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发表时间：
2017-02-15
影响因子：
5
通讯作者：
Greig, A.
中科院分区：
文献类型：
--
作者：
Belli, R.;Borsato, A.;Greig, A.
微量元素和Sr同位素记录在两个同时代的石笋，其特征在于不同的生长速率和流量制度在萨维洞（格罗塔萨维，NE意大利）揭示了不同的来源和合并机制Mg和Sr。Mg主要来源于溶解的洞穴寄主岩石，而来自土壤的颗粒Mg起着次要的作用。颗粒载镁的存在下推断的Mg和颗粒相关的元素（Th，Al和Mn），这是优先集中在开放的柱状方解石层的共同变化。Mg浓度的变化校正颗粒影响的组件，Mg-C参数，是由水-岩相互作用，较高和较低的Mg-C在干和湿阶段，分别控制。这被认为反映了富镁相的不一致溶解。基于Sr-87/Sr-86比值，校正了空气中外源Sr的贡献，得到了仅为Sr-c的贡献。石笋方解石中Sr-C的变化受洞穴沉积物生长速率和方解石-水Sr分配在湿相和干相的变化的影响，只有在很小程度上由富Mg相的不一致溶解。Mg-c和Sr-cg的浓度分布（生长速率效应校正）显示出负相关性，并推断出水文意义，这是捕获在水文指数，HI。我们建议，HI提供了强大的信息，水-岩相互作用有关的水文变化，可用于在潮湿和半干旱环境中，土壤镁和外源锶的校正可以应用的信心。HI指数的应用允许Grotta Savi氧同位素数据的校正，以产生一个Δ O-18（c）时间序列，显示何时水分来源和大气重组的变化，或水分量的变化是显着的。这在新仙女木（Younger Dryas，YD）时期尤为明显。萨维记录支持的概念，一个两阶段的YD，标志着增加的水分和更强的影响，亚得里亚海和地中海的影响在北方亚得里亚海地区从12.3万年起。然后，一个大规模的大气重组和逐步北移的极锋造成了逐步减少海洋的影响，该地区从12.1万年，支持的概念，半球变化。(C)2016爱思唯尔有限公司版权所有。
The trace element and Sr isotope records in two coeval stalagmites characterized by different growth rates and flow regimes at Savi cave (Grotta Savi, NE Italy) reveal different sources and incorporation mechanisms for Mg and Sr. Mg is sourced primarily from dissolved cave host rock while particulate Mg derived from soil plays a subordinate role. The presence of particulate-borne Mg is inferred from the co-variation of Mg and particle-associated elements (Th, Al and Mn) which are preferentially concentrated in open columnar calcite layers. Variation in Mg concentrations corrected for particleinfluenced components, the Mg-c parameter, is controlled by water-rock interaction, with higher and lower Mg-c during dry and wet phases, respectively. This is thought to reflect incongruent dissolution of Mg-rich phases. Correction of Sr concentrations for contributions from airborne exogenic Sr, based on Sr-87/Sr-86 ratios, yields the bedrock-only contribution (Sr-c). Sr-c variation in stalagmite calcite is influenced by speleothem growth rate and by variation of the calcite-water Sr partitioning in wet and dry phases, and only to a minor extent by incongruent dissolution of Mg-rich phases. Concentration profiles for Mg-c and Sr-cg (corrected for growth rate effects) show inverse correlations and are inferred to show hydrological significance which is captured in a hydrological index, HI. We suggest HI provides robust information on water-rock interaction related to hydrological changes and can be utilized in both wet and semi-arid environments, provided the corrections for soil Mg and exogenic Sr can be applied with confidence. Application of the HI index allows correction of Grotta Savi oxygen isotope data, to yield a delta O-18(c) time series that shows when changes in moisture sources and atmospheric reorganization, or changes in moisture amount, were significant. This is especially evident during the Younger Dryas (YD). The Savi record supports the concept of a two-phase YD, marked by an increase of moisture and stronger impact of Adriatic and Mediterranean Sea influences over the northern Adriatic region from 12.3 ka onwards. Then, a large-scale atmospheric reorganization and gradual northward shift of the Polar Front caused a progressive reduction of sea influence over the region from 12.1 ka, supporting the concept of a hemispheric change. (C) 2016 Elsevier Ltd. All rights reserved.