Changes in the Provenance of the Holocene Deposits of the Oga and Tsivolki Bays (Novaya Zemlya Archipelago) according to Sr, Nd, and Pb Isotope Data

IF 0.7 4区 地球科学 Q4 GEOCHEMISTRY & GEOPHYSICS
I. A. Vishnevskaya, Yu. A. Kostitsyn, T. G. Okuneva, N. G. Soloshenko
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引用次数: 0

Abstract

The paper considers Sr, Nd, and Pb isotope data obtained for two cores of bottom sediments taken in the Oga and Tsivolki bays of Severny Island of the Novaya Zemlya archipelago. The studied sequence of sediments from Oga Bay has accumulated over the last thousand years. The 87Sr/86Sr ratio decreases from top to bottom down the section from 0.72225 to 0.71995, the value of εNd varies from –6.1 to –5.5. The Pb isotopic composition varies within narrow limits: the 206Pb/204Pb ratio from 19.107 to 19.139, the 207Pb/204Pb ratio from 15.632 to 15.635, and the 208Pb/204Pb ratio from 38.568 to 38.635. A rapid decrease in the 87Sr/86Sr ratio at a relatively stable neodymium and lead isotope composition indicates a change in the source of the clastic material. This can be explained by the fact that the material of the destruction of Permian clay shales, and then Devonian–Silurian sedimentary carbonates, first entered the area of glacier abrasion and further, respectively, into the sedimentation zone. The sediment column from Tsivolki Bay was formed over a little more than 10 000 years. Based on the Sr, Nd, and Pb isotope ratios, these bottom sediments are divided into lower and upper parts: before and after 150 cm (or ~3500 years). In the lower part of the column, the 87Sr/86Sr ratio increases from 0.72055 to 0.72580, the value of εNd remains approximately the same and varies around –8.2. In the upper part, the 87Sr/86Sr ratio drops to 0.72049 in the near-surface layer; at the same time, the value of εNd increases to –6.4. At the boundary of these two units, the 206Pb/204Pb ratio abruptly changes from about 18.0 in the lower part to 19.3 in the upper part and 208Pb/204Pb from about 36.5 in the lower part to 38.7 in the upper part of the section. The change in the Sr, Nd, and Pb isotope characteristics is likely a reflection of changes in the composition of the rocks in the area where the basin was removed, which is now being eroded by the glacier. Comparison with modern sources supplying clastic material to the Kara Sea showed that the material is supplied to the Oga and Tsivolki bays only from Novaya Zemlya.

Abstract Image

Abstract Image

根据锶、钕和铅同位素数据研究奥加海湾和齐沃尔基海湾(新泽姆利亚群岛)全新世沉积物产地的变化
本文研究了在新亚泽姆利亚群岛塞维里岛奥加湾和齐沃尔基海湾采集的两块海底沉积物岩芯中获得的锶同位素、钕同位素和铅同位素数据。所研究的奥加湾沉积物序列是在过去一千年中累积而成的。87Sr/86Sr 比率从上到下从 0.72225 降至 0.71995,εNd 值从 -6.1 降至 -5.5。Pb同位素组成的变化范围很窄:206Pb/204Pb比值从19.107到19.139,207Pb/204Pb比值从15.632到15.635,208Pb/204Pb比值从38.568到38.635。在钕和铅同位素组成相对稳定的情况下,87Sr/86Sr 比率迅速下降,表明碎屑物质的来源发生了变化。这可以解释为二叠纪粘土页岩的破坏物质,然后是泥盆纪-志留纪沉积碳酸盐,首先进入冰川磨蚀区,然后分别进入沉积区。齐沃尔基海湾的沉积柱是在一万多年前形成的。根据锶、钕和铅同位素比值,这些底部沉积物可分为上下两部分:150 厘米之前和之后(或约 3500 年)。在柱体的下部,87Sr/86Sr 的比值从 0.72055 增加到 0.72580,εNd 的值基本保持不变,变化在 -8.2 左右。在上部,近表层的 87Sr/86Sr 比率下降到 0.72049;同时,εNd 值上升到 -6.4。在这两个单元的交界处,206Pb/204Pb比值从下部的约18.0骤变到上部的19.3,208Pb/204Pb比值从下部的约36.5骤变到上部的38.7。锶、钕和铅同位素特征的变化很可能反映了盆地被移走地区岩石成分的变化,该地区目前正受到冰川的侵蚀。与向喀拉海提供碎屑物质的现代来源进行比较后发现,向奥加海湾和齐沃尔基海湾提供的物质仅来自新亚泽姆利亚。
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来源期刊
Geochemistry International
Geochemistry International 地学-地球化学与地球物理
CiteScore
1.60
自引率
12.50%
发文量
89
审稿时长
1 months
期刊介绍: Geochemistry International is a peer reviewed journal that publishes articles on cosmochemistry; geochemistry of magmatic, metamorphic, hydrothermal, and sedimentary processes; isotope geochemistry; organic geochemistry; applied geochemistry; and chemistry of the environment. Geochemistry International provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.
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