Quantitative salinity reconstructions of the Baltic Sea during the mid‐Holocene
Quantitative salinity reconstructions of the Baltic Sea during the mid‐Holocene
复制标题
全新世中期波罗的海盐度定量重建
作者：
W. Ning;P. Andersson;Anupam Ghosh;Mansoor Khan;H. Filipsson
我们重建了波罗的海大约从公元 1000 年起过去的沿海环境。 7300 至 3500 卡。 a BP，重点关注海面盐度 (SSS)。为了定量确定 SSS，采用了两种方法：测量软体动物壳中的 87Sr/86Sr 比率 (SSSSr) 和甲藻包囊 Operculodinium centrocarpum (SSSpl) 的过程长度变化。 SSSSr 在 6800 至 6400 cal 之间约为 6-7。 BP，类似于现代条件。 6000 至 3900 cal 之间。 a BP、SSSSr 始终较高，范围在 ~9 到 13 之间。对盐度变化敏感的微化石，如 Radiosperma corbiforum 和 Spiniferites spp.，支持 SSSSr 估计。与 SSSSr 相比，SSSpl 值始终较高，平均约为 14。我们认为 SSSpl 倾向于高估盐度，并且不如 SSSSr 可靠。多代理方法，包括微化石、有机碳含量、碳氮比和粒度的分析，允许将研究期分为三个区域（区域 I-III）。 I 区（7300-6400 cal. a BP）的特点是相对的 O. centrocarpum 和 R. corbiforum 浓度、淤泥含量和 C/N 比，对应于区域 Littorina 海侵最大值。 II 区（6400–3900 cal.a BP）的特点是刺松属植物数量增加。和 R. corbiforum 丰度降低，以及相对于 I 区降低的 C/N 比和淤泥含量。 III 区（3900-3500 cal. a BP）代表后滨海阶段的开始，表明向现代波罗的海阶段的转变，盐度降低。
We reconstructed the past coastal environment of the Baltic Sea from c. 7300 to 3500 cal. a BP, with a focus on sea surface salinity (SSS). To quantitatively determine the SSS, two methods were employed: measurements of 87Sr/86Sr ratios in mollusc shells (SSSSr) and process length variations of dinoflagellate cysts Operculodinium centrocarpum (SSSpl). The SSSSr was ~6–7 between 6800 and 6400 cal. a BP, similar to modern conditions. Between 6000 and 3900 cal. a BP, SSSSr was consistently higher, ranging between ~9 and 13. Microfossils sensitive to salinity variations, such as Radiosperma corbiforum and Spiniferites spp., support the SSSSr estimate. In comparison with the SSSSr, the SSSpl values were consistently higher, with an average of ~14. We suggest SSSpl tend to overestimate salinity and are not as reliable as SSSSr. A multi‐proxy approach, including analysis of microfossil, organic carbon content, C/N ratios and grain‐size, allowed for a division of the study period into three zones (Zones I–III). Zone I (7300–6400 cal. a BP) is characterized by relatively O. centrocarpum and R. corbiforum concentrations, silt contents and C/N ratios, corresponding to the regional Littorina transgression maximum. Zone II (6400–3900 cal. a BP) is characterized by increased Spiniferites spp. and decreased R. corbiforum abundances, and by lowered C/N ratios and silt contents relative to Zone I. Zone III (3900–3500 cal. a BP) represents the start of the Post‐Littorina Sea phase, indicating a shift to the modern Baltic Sea phase with decreased salinity.