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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Glacial hydrologic conditions in the Black Sea reconstructed using geochemical pore water profiles
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Glacial hydrologic conditions in the Black Sea reconstructed using geochemical pore water profiles

机译：利用地球化学孔隙水剖面重建黑海的冰川水文条件

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摘要

Chloride and δ~(18)O compositions of interstitial water extracted from a long sediment core retrieved from the NW coast of the Black Sea allowed us to constrain the main hydrologic changes of the Back Sea during the Late Pleistocene and Holocene. Prior to its reconnection with the Mediterranean Sea (through the Marmara Sea) at approximately 9000 calendar yr before present (9kacalBP), the Black Sea has evolved as a fresh to brackish water lake. At the time of reconnection, hydrologic changes were drastic. Bottom water salinities changed from a few psu (practical salinity unit) to ~22psu. Since solutes in the interstitial water column within sediments are advected and diffused the measured concentrations do not reflect those of past bottom waters. In order to reconstruct these former concentrations, we used an advection/diffusion model. Different scenarios of bottom water chloride and δ~(18)O variations were accounted for in this model in order to simulate "present day" vertical profiles for concentrations of interstitial water in order to compare them to measured ones. The comparison suggests that the glacial Black Sea was a homogeneous freshwater lake (with a δ~(18)O of ~-10‰ and a salinity of ~1psu). Modern hydrologic conditions would only have been reached at ~2kacalBP, concomitant with the onset of coccolith-rich thin layers that characterize modern basin sediments. Such delayed salinization (over ~7000yr) in the basin may have been due to higher precipitation during the early Holocene. We also simulated the impact of a catastrophic reconnection and a smoother reconnection. Both salinity scenarios lead to undistinguishable modelled "present day" profiles, indicating that the precise impact of the last reconnection was lost due to the advection/diffusion processes.
机译：从黑海西北缘取回的长沉积岩心中提取的间隙水的氯和δ〜（18）O组成，使我们能够控制晚更新世和全新世后海的主要水文变化。在大约9000历年（9kacalBP）之前，黑海与地中海重新连接（通过马尔马拉海）之前，黑海已经发展成为淡淡的咸淡水湖。重新连接时，水文变化剧烈。底水盐度从几psu（实用盐度单位）变为〜22psu。由于沉积物中间隙水柱中的溶质被平流并扩散，因此测得的浓度不能反映过去的底水浓度。为了重建这些先前的浓度，我们使用了对流/扩散模型。在该模型中考虑了底部氯化​​物和δ〜（18）O变化的不同情况，以便模拟间隙水浓度的“现今”垂直剖面，以便将其与实测水进行比较。比较表明，冰川黑海是一个均质的淡水湖（δ〜（18）O为〜-10‰，盐度为〜1psu）。现代水文条件只能在〜2kacalBP左右才能达到，同时伴随着富含可可巨石的薄层的出现，这是现代盆地沉积物的特征。流域盐碱化延迟（超过7000年）可能是由于全新世早期降水增加。我们还模拟了灾难性重新连接和更平滑的重新连接的影响。两种盐度情景均导致无法区分的“当前”轮廓模型，这表明由于对流/扩散过程而失去了最后一次重新连接的精确影响。

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