Unraveling natural and human-accelerated erosional and weathering processes in the past: The new "comminution dating" approach based on uranium isotope analyses applied on a lake sediment record

揭示过去自然和人为加速的侵蚀和风化过程：基于铀同位素分析的新“粉碎测年”方法应用于湖泊沉积物记录

基本信息

批准号：
324893917
负责人：
Dr. Alexander Francke
金额：
--
依托单位：
Wollongong Isotope Geochronology Laboratory (WIGL)
依托单位国家：
德国
项目类别：
Research Fellowships
财政年份：
2016
资助国家：
德国
起止时间：
2015-12-31 至 2018-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/324893917?language=en
关键词：
Unraveling natural human accelerated erosional

项目摘要

Erosion and weathering are predominately controlled by tectonic uplift and climate conditions and are therefore affected by natural variations. Rapid anthropogenic induced climate warming can trigger distinct modifications in these processes in the near future. Furthermore, anthropogenic wood clearance and agricultural land use can accelerate the erosion in the terrestrial realm. Although a profound understanding of how erosion and weathering form landscapes are fundamentally important for future predictions, appropriate analytical methods for linking the history of erosion and weathering to paleoenviromntal and -climatic proxy data in the geological history are sparse. A new promising method to close this gap of knowledge is the application of uranium isotope analyses on clastic sediment material, which enables the determination of the so-called comminution age, i.e. the time that has elapsed since a detrital grain was formed by weathering. By comparing the comminution age with the depositional age in a sedimentary basin, erosional processes and catchment dynamics can be quantified. A long residence time of clastic material in the weathering horizon (long regolith residence time) suggests slow removal of topsoil material by sheet wash, whereas a short regolith residence time points to an intensification and deepening of the denudation by gully erosion. This relatively new method shall be applied on a lacustrine sediment succession from Lake Ohrid (Macedonia, Albania). The paleoclimatic and -environmental history of Lake Ohrid is already well studied by using sedimentologic, (bio-)geochemical, isotope (O, C), and pollen data. This information will be combined with the uranium isotope data in order to investigate the link between climate, environment and erosion. Thereby, particular focus will be drawn on the human impact on the landscape evolution by wood clearance and agricultural land-use during the Late Holocene period. Since uranium isotope analysis as a proxy for past landscape evolution is a relatively new approach and was not applied to lake sediment successions until today, the proposed research project also encompasses a calibration and evaluation of the method. Chemical pre-treatment methods will be tested for their applicability on lake sediments, and the conceptual model of sheet wash versus gully erosion will be studied on (sub-)recent sediments from Darwin Harbor (Northern Territory, Australia). Erosional processes in the catchment area of Darwin Harbor can geographically be separated into two endmembers, characterized by sheet wash and gully erosion, respectively. This study enables a detailed examination if the signal of these two erosion types can be detected in the Darwin Harbor sediments by means of uranium isotope analyses.

侵蚀和风化主要由构造隆升和气候条件控制，因此受自然变化的影响。在不久的将来，在这些过程中，快速的人为诱导的气候变暖会触发不同的修改。此外，人为的木材清除和农业土地使用可以加速陆地领域的侵蚀。尽管对侵蚀和风化形式的景观的深刻了解对于未来的预测至关重要，但是适当的分析方法是将侵蚀和风化的历史与古细胞和批准的代理数据联系起来。弥合这一知识差距的一种新的有前途的方法是在碎屑沉积物材料上的铀同位素分析的应用，这可以确定所谓的粉碎年龄，即自从潮湿谷物以来已经通过风化形成以来已经过去的时间。通过比较沉积物盆地中的浓度年龄与沉积年龄，可以量化侵蚀过程和集水动力学。在风化的地平线中碎屑材料的长时间停留时间（长岩石停留时间）表明，通过薄纸清洗对表层土壤的材料缓慢去除，而短的岩石停留时间则指向通过吞噬侵蚀的强化和深化腐蚀。这种相对较新的方法应适用于来自奥奥尔德湖（马其顿，阿尔巴尼亚）的湖泊沉积物。通过使用沉积学，（生物）地球化学，同位素（O，C）和花粉数据，已经对Ohrid湖的古气候和环境历史进行了很好的研究。该信息将与铀同位素数据结合使用，以研究气候，环境和侵蚀之间的联系。因此，在全新世晚期，将特别关注人类对木材清除和农业土地利用的影响的影响。由于铀同位素分析作为过去景观演化的代理是一种相对较新的方法，直到今天才适用于湖泊沉积物的继任方法，因此拟议的研究项目还涵盖了该方法的校准和评估。化学预处理方法将在湖泊沉积物上的适用性进行测试，并将在（澳大利亚北领地）达尔文港（亚地区的亚）沉积物上研究板清与沟壑侵蚀的概念模型。达尔文港集水区的侵蚀过程在地理上可以分为两个末端成员，分别以清洗板和沟渠的侵蚀为特征。这项研究可以通过铀同位素分析在达尔文港沉积物中检测到这两种侵蚀类型的信号。