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Patterns of erosion in the Western Alps and quantification of sediment reworking in the associated Po River foreland basin

西阿尔卑斯山的侵蚀模式和相关波河前陆盆地沉积物改造的量化

基本信息

批准号：
258542216
负责人：
Dr. Hella Wittmann-Oelze
金额：
--
依托单位：
Dipartimento di Scienze Ambiente e Territorio e Scienze della Terra (DISAT)
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2014
资助国家：
德国
起止时间：
2013-12-31 至 2015-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/258542216?language=en
关键词：
Patterns erosion Western Alps quantification

项目摘要

Tectonically active mountain belts generate sediment that is, on its journey to the sea, intermittently stored in foreland basins, where it undergoes episodes of temporary storage and reworking. This reworking results in buffering of the eroded sediment fluxes that is caused by diffusive sediment transport and channel-floodplain interaction, causing a missing link in the source-sink connection. As a result, forces like climate cycling controlling sediment export cannot be linked directly to preserved sedimentary successions. The Po drainage basin is an excellent test site to evaluate the timescales and magnitudes of sediment transport and mixing patterns, as it integrates over the rapidly eroding Western and Central European Alps, as well as the Northern Apennines, and the low-relief Po floodplain storing vast amounts of post-orogenic detritus. Until now, widespread recycling of Alpine detritus in the Apenninic accretionary wedge and low apatite and zircon fertility in the Apennines compared to the Alps limited the application of e.g. heavy mineral suites for source rock discrimination and sediment transport. Here, we propose to use a unique combination of mineral fertility analysis and triple in situ-produced cosmogenic nuclides to resolve this challenge. We will first characterize the source areas for their erosion signal using cosmogenic 10Be, then will analyze their downstream changes in relative sediment contributions in the Po plain by using 26Al/10Be ratios in comparison to then known cosmogenic and petrographic source-area fingerprints, and finally, we will determine stable 21Ne concentrations that will allow to assess the residence time of sediment in the Po foreland basin. This approach will lead to a better understanding of reworking of sedimentary deposits and time scales of sediment storage potentially buffering and thus modifying the source area´s erosional signal. Outcomes of this proposal are expected to increase the awareness for the fact that 1) detrital sediments are not transported instantaneously to the sea after their erosion in the source area, 2) that the geochemical fingerprint of such sediments might be integrative over an unknown transfer time, and 3) finally that the sedimentary archive may not necessarily preserve the direct products of erosion episodes but that these may have been modified during floodplain transfer.

构造活跃的山带产生的沉积物，在其出海的途中，间歇性地储存在前陆盆地中，在那里经历了临时储存和重新加工的时期。这种改造导致了由扩散泥沙输送和河道-泛滥平原相互作用引起的侵蚀泥沙通量的缓冲，导致源-汇连接中的一个缺失环节。因此，像气候循环这样控制沉积物输出的力量不能直接与保存下来的沉积序列联系起来。Po流域盆地是评估沉积物运移和混合模式的时间尺度和大小的极佳试验场，因为它整合了快速侵蚀的西欧和中欧阿尔卑斯山、北部亚平宁山脉和储存着大量造山后碎屑的低起伏Po泛滥平原。到目前为止，高山碎屑在亚平宁期增生楔中的广泛循环，以及亚平宁山脉与阿尔卑斯山相比，磷灰石和锆石丰度较低，限制了重矿物套件在源岩识别和沉积物搬运方面的应用。在这里，我们建议使用矿物肥力分析和三种原位生产的宇宙核素的独特组合来解决这一挑战。我们将首先利用宇宙成因的10Be来表征其侵蚀信号的源区，然后将利用26Al/10Be比值与当时已知的宇宙成因和岩石源区指纹相比较，分析它们在Po平原相对沉积物贡献的下游变化，最后我们将确定稳定的21Ne浓度，以评估沉积物在Po前陆盆地的停留时间。这种方法将有助于更好地理解沉积沉积的改造和沉积物储存的时间尺度，潜在地缓冲并修正源区的S侵蚀信号。这一建议的结果可望提高人们对以下事实的认识：1)碎屑沉积物在源区受到侵蚀后不会立即运往海洋，2)这类沉积物的地球化学指纹在未知的转移时间内可能是完整的，3)沉积档案不一定保存侵蚀事件的直接产物，但这些指纹可能在洪泛平原转移过程中被修改。