Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)
Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)
复制标题
DOI：
10.5194/esurf-6-141-2018
复制
发表时间：
2017-09
期刊：
影响因子：
--
通讯作者：
R. Hindshaw;N. Tosca;A. Piotrowski;E. Tipper
中科院分区：
文献类型：
--
作者：
R. Hindshaw;N. Tosca;A. Piotrowski;E. Tipper
抽象的。确定海洋沉积物来源是利用海洋沉积物岩心提取有关过去气候和海洋环流的信息的先决条件。锶、钕同位素是追踪物源来源的经典工具。尽管人们对北冰洋有相当大的兴趣，但从锶和钕的同位素组成来看，环北极源区的特点很差。本文介绍了斯瓦尔巴特群岛古近纪中央盆地沉积物的锶、钕同位素数据，其中包括首次发表的斯瓦尔巴群岛水系悬浮物的数据。水系悬浮物具有相当大的同位素变化(e_(ND)=−20.6~−_(13.4)；87Sr/86Sr=0.73421~0.74704)，这可能与其形成的沉积建造的沉积历史有关。结合集水岩和沉积物的粘土矿物学分析，认为中央盆地沉积岩具有两种来源。一种是来自格陵兰基底岩的元古界沉积物，富含伊利石，具有高的87Sr/86Sr和低的e-Nd值。二是西伯利亚玄武岩中的石炭-侏罗纪沉积物，富含蒙脱石，具有较低的87Sr/86Sr和较高的e-Nd值。由于整个古近纪(从深海到陆相)沉积条件的变化，这两种物源在中央盆地建造中的相对比例不同。现代水系悬浮物的同位素组成受现代作用，特别是冰川作用的控制，这决定了地层的现今暴露程度，从而决定了每个地层对水系悬沙负荷的相对贡献。这项研究表明，水系悬浮物的ND同位素组成具有季节性变化，这可能反映了较长期的水文变化，这对基于固定端元随时间变化的物源研究具有重要意义。
Abstract. The identification of sediment sources to the ocean is a prerequisite to using marine sediment cores to extract information on past climate and ocean circulation. Sr and Nd isotopes are classical tools with which to trace source provenance. Despite considerable interest in the Arctic Ocean, the circum-Arctic source regions are poorly characterised in terms of their Sr and Nd isotopic compositions. In this study we present Sr and Nd isotope data from the Paleogene Central Basin sediments of Svalbard, including the first published data of stream suspended sediments from Svalbard. The stream suspended sediments exhibit considerable isotopic variation ( e Nd = − 20.6 to − 13.4; 87 Sr ∕ 86 Sr = 0.73421 to 0.74704) which can be related to the depositional history of the sedimentary formations from which they are derived. In combination with analysis of the clay mineralogy of catchment rocks and sediments, we suggest that the Central Basin sedimentary rocks were derived from two sources. One source is Proterozoic sediments derived from Greenlandic basement rocks which are rich in illite and have high 87 Sr ∕ 86 Sr and low e Nd values. The second source is Carboniferous to Jurassic sediments derived from Siberian basalts which are rich in smectite and have low 87 Sr ∕ 86 Sr and high e Nd values. Due to a change in depositional conditions throughout the Paleogene (from deep sea to continental) the relative proportions of these two sources vary in the Central Basin formations. The modern stream suspended sediment isotopic composition is then controlled by modern processes, in particular glaciation, which determines the present-day exposure of the formations and therefore the relative contribution of each formation to the stream suspended sediment load. This study demonstrates that the Nd isotopic composition of stream suspended sediments exhibits seasonal variation, which likely mirrors longer-term hydrological changes, with implications for source provenance studies based on fixed end-members through time.