Strontium isotopic composition of modern and Holocene mollusc shells as a palaeosalinity indicator for the Baltic Sea
Strontium isotopic composition of modern and Holocene mollusc shells as a palaeosalinity indicator for the Baltic Sea
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DOI：
10.1016/j.chemgeo.2006.02.010
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发表时间：
2006-08
期刊：
影响因子：
3.9
通讯作者：
A. Widerlund;P. Andersson
中科院分区：
文献类型：
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作者：
A. Widerlund;P. Andersson
来自凸起海滩沉积物的亚化石碳酸盐软体动物壳中的 87Sr/86Sr 同位素比率被用作波罗的海的古盐度指标。主要目的是证明该方法在以前的冰川区域的适用性，使用现代贝壳（贻贝、Macoma baltica 和 Radix balthica）中发现的 87Sr/86Sr 比率来阐明用于基于亚化石贝壳进行古盐度测定的参数和条件。假设波罗的海海水中的 Sr 浓度由海水和河水之间的二元保守混合控制，计算代理盐度数据。基于对现代贝壳中 87Sr/86Sr 比率的重复测定，可以以优于 ±5% 的相对精度（对于高达~10‰的盐度）来量化代理盐度数据。与当前测量的盐度进行比较表明，代理数据的精度通常优于 ±5%。凭借这种精度和准确性，可以检测到波罗的海主要次盆地（波提尼亚湾、波提尼亚海和波罗的海本部）之间目前的盐度差异。使用亚化石贝壳（M. edulis 和 M. baltica）测定古盐度，校准 14 C 年龄为 6770–3070 cal BP。贝壳沉积物位于海拔 65m 处。下降到现在的海平面。确定的波的尼亚湾（4.8–10.3‰）和波的尼亚海（7.3–10.3‰）的古盐度与早期对这些次盆地最大滨海阶段古盐度的估计（8–10‰）非常吻合。在一处地点，对同一贝壳沉积物中的两种不同贝类进行了测年（M. edulis 和 M. baltica）。这些贝壳的年龄相差 460±7014C 年，这可能表明某个地点的生态条件可能在不同时期有利于不同的动物群。
The87Sr/86Sr isotope ratio in subfossil carbonate mollusc shells from raised-beach sediments is used as a palaeosalinity indicator for the Baltic Sea. The main purpose is to demonstrate the applicability of the method in a formerly glaciated area, using87Sr/86Sr ratios found in modern shells (Mytilus edulis, Macoma baltica, and Radix balthica) to elucidate the parameters and conditions to be used for palaeosalinity determinations based on subfossil shells. Proxy salinity data are calculated assuming that the Sr concentration in Baltic Sea water is controlled by a two-component, conservative mixing between seawater and river water. Based on replicate determinations of the87Sr/86Sr ratio in modern shells, proxy salinity data can be quantified with a relative precision of better than ±5% for salinities up to ∼10‰. Comparison with measured, present-day salinities indicates that the accuracy is generally better than ±5% for the proxy data. With this precision and accuracy, the present-day salinity differences between the major Baltic sub-basins (Bothnian Bay, Bothnian Sea, and Baltic Proper) can be detected. Palaeosalinities were determined using subfossil shells (M. edulis and M. baltica) with calibrated14C ages of 6770–3070 cal BP. The shell deposits occur from 65m a.s.l. down to the present-day sea level. The palaeosalinities determined for the Bothnian Bay (4.8–10.3‰) and the Bothnian Sea (7.3–10.3‰) are in good agreement with earlier estimates of the maximum Littorina Sea stage palaeosalinity in these sub-basins (8–10‰). At one locality, two different shell species from the same shell deposit were dated (M. edulis and M. baltica). The shells differed in age by 460±7014C years, a possible indication that the ecological conditions at a locality may have been favourable to different faunas at different times.