Water depth and diagenetic constraints on the use of barium as a palaeoproductivity indicator
Water depth and diagenetic constraints on the use of barium as a palaeoproductivity indicator
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水深和成岩作用对使用钡作为古生产力指标的限制
DOI：
10.1144/gsl.sp.1992.064.01.18
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
E. Suess
中科院分区：
文献类型：
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作者：
Marta T. Von Breymann;K. Emeis;E. Suess
在太平洋和印度洋沿岸上升流和赤道辐散带的高生产力区下面的沉积物中，钡是富集的，在此基础上，沉积物中的钡含量一直被认为是潜在的古生产力指标。对秘鲁边缘沉积物的分析证实了深海初级生产力高的地区钡积累增强的模式，但也表明这种模式不能扩展到浅水沉积物。来自秘鲁大陆架的沉积物缺乏任何钡富集，而在水深超过2000米的斜坡和盆地沉积物中，钡元素显著富集。位于快速下沉的利马盆地的682号站点进一步说明了这种深度效应。水深>3000 m的第四系沉积物富含有机碳、蛋白石和生物钡。中新世沉积物，虽然沉积在高生产力的沃茨与沿海上升流中心，没有显示富集钡记录对应的非常高的有机碳和蛋白石的水平;模式是一致的沉积在浅水盆地。除了水深对钡分布的影响外，在经历强缺氧成岩作用的上升流区沉积物中可以观察到原生信号的叠加。微晶重晶石部分溶解在间隙硫酸盐耗尽的间隔所示的沉积物从秘鲁边缘。溶解的硫酸盐耗尽的间隔的深水段的重晶石导致高钡浓度附近的硫酸盐还原区，向下的硫酸盐和向上的钡扩散促进当地的重晶石沉淀在成岩前沿的终端。在深水沉积地点的沉积氧和亚氧环境中的钡分布具有很高的潜力，作为古生产力指标;然而，在不同水深的地区和缺氧成岩环境中，应谨慎使用钡积累作为海洋肥力的代表，在这些地区，硫酸盐耗竭使间隙沃茨相对于重晶石不饱和。
Abstract Sediments underneath the high productivity areas of the coastal upwelling and equatorial divergence zones in the Pacific and Indian oceans are enriched in barium, and on this basis the barium content of the sediments has long been suggested as a potential palaeoproductivity indicator. Analyses of sediments from the Peru margin corroborate the pattern of enhanced barium accumulation in areas of high primary productivity in the deep ocean, but also show that this pattern cannot be extended to shallow-water deposits. Sediments from the Peru shelf lack any barium enrichment, whereas this element is significantly enriched in slope and basinal deposits in water columns deeper than 2000 m. This depth effect is further illustrated at Site 682 located in the rapidly subsiding Lima Basin. The Quaternary sequence deposited at water depths >3000 m is enriched in organic carbon, opal and biogenic barium. The Miocene sediments, although deposited under highly productive waters associated with a coastal upwelling centre, do not show an enrichment in the barium record corresponding to the very high organic carbon and opal levels; a pattern that is consistent with deposition in shallow basins. In addition to the effect of water depth on the barium distribution, overprinting of primary signals can be observed in sediments from upwelling areas undergoing strong anoxic diagenesis. Microcrystalline barite is partly dissolved in intervals depleted in interstitial sulphate as shown for sediments from the Peru margin. Dissolution of barite in sulphate depleted intervals of deep water sections leads to high barium concentrations near the termination of the sulphate reducing zone, where downward sulphate and upward barium diffusion foster local barite precipitation in diagenetic fronts. The barium distribution in sedimentary oxic and suboxic environments at deep water depositional sites has a high potential as a palaeoproductivity indicator; however, barium accumulation as a proxy for ocean fertility should be used with caution in areas of varying water depths and in anoxic diagenetic environments where sulphate depletion undersaturates the interstitial waters with respect to barite.
Becker, K.：“海洋钻探计划的记录”初步报告。
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