Linking erosion and the sediment record : detrital thermochronology in the Taiwan

连接侵蚀和沉积记录：台湾的碎屑热年代学

基本信息

批准号：
NE/E012426/1
负责人：
Linda Kirstein
金额：
$ 34.67万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Fellowship
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FE012426%2F1
关键词：
Linking erosion sediment record detrital

项目摘要

Whether tectonic activity or climate is the driving force behind the major uplift of mountains during Cenozoic times is a lively modern controversy in tectonic geomorphology. Since this chicken or egg debate was instigated by Peter Molnar and Philip England in 1990 much effort has been invested in determining whether tectonic activity has driven long term climate change or vice versa. However we are only just beginning to understand some of the complex interplay between climate and tectonics and how this shapes the landscape that surrounds us. What is required is greater resolution to solve the problem through an integrated, cross-disciplinary approach. I propose to use both the modern and ancient record of sediment supply from the Central Ranges of eastern Taiwan to investigate long term erosion rates and document whether climate or tectonic activity dominates the erosion record in this active orogen. End member scenarios where climate or tectonic activity dominates the signal will be modelled independently using a surface dynamic model thereby potentially fingerprinting climate versus tectonic forcing in ancient sedimentary records. To tackle this problem I intend to focus on Taiwan due to the high rates of rock uplift and erosion recorded there which reflect both the convergent tectonic setting and sub-tropical climate. Taiwan although small has a major global impact as it contributed almost 2% of the total global suspended sediment entering the ocean in the last 30 years. Such high rates of erosion are not sustainable over prolonged periods of time, as no high grade metamorphic rocks have been exhumed in the core of the orogen, yet average erosion rates since the beginning of collision in the Late Miocene are comparable with average historic erosion rates. Understanding what drives erosion in this setting through time is the ambition of this project. Ultimately the results will help determine how the effects of climate and/or tectonic forcing are preserved in ancient sediment archives and in future help to evaluate the importance of climate versus tectonic forcing in the sedimentary record over geological time. The fluvial response to exhumation in an antecedent river system will be documented and long term erosion rates in both modern and ancient detrital sediments determined using low temperature thermochronometers or geological clocks. The clock concept can be used as a basic tool in investigating what happens to a rock as it first moves from depth towards the surface and then is eroded and finally deposited in a basin. The concept as applied here is based on the fact that minerals become closed to the diffusion of particular elements at particular temperatures. Once closed the clock start to tick and information on the cooling history of the sample is accumulated. If the depositional age of the sample is known, from either magnetostratigraphy or nanofossils, then the time taken by the sample to pass through closure and be exhumed from depth and deposited in the basin can be calculated. The erosion rate can then be inferred by thermal modelling. Current investigations tend to be either model biased or field biased and not well integrated. As a result, once I have collected the data concerning erosion rates both in the Pliocene and Quaternary sequences I aim to apply the surface dynamic model CHILD to modelling sediment flux and fluvial response to long term exhumation forced by climate and/or tectonic variation. The model results will be generated to closely mirror what is preserved in the sediment archive and help distinguish between climate and tectonic forcing in the erosion record. If this is achieved I shall have improved our understanding of how these processes shape the Earth's surface and taken a large step towards linking erosion history with the sediment record.

在新生代时期，构造活动还是气候是山区主要升高背后的驱动力是构造地貌的活泼现代争议。由于彼得·莫尔纳尔（Peter Molnar）和菲利普·英格兰（Philip England）在1990年煽动了这场鸡或鸡蛋辩论，因此在确定构造活动是否导致长期气候变化还是反之亦然方面投入了很多努力。但是，我们才刚刚开始了解气候和构造之间的某些复杂相互作用，以及这如何塑造我们周围的景观。需要的是更大的解决方案，可以通过综合的跨学科方法解决问题。我建议利用台湾东部中央范围的现代和古代沉积物供应记录来研究长期侵蚀率，并记录气候还是构造活动是否主导着这种活跃的造山基因的侵蚀记录。气候或构造活动主导信号的最终成员场景将使用表面动态模型独立建模，从而在古代沉积记录中潜在地指纹与构造强迫进行指纹构成。为了解决这个问题，我打算将重点放在台湾上，因为那里记录了岩石隆起和侵蚀的速度，这既反映了收敛的构造环境和亚热带气候。台湾虽然Small具有重大的全球影响力，因为它在过去30年中贡献了进入全球悬浮沉积物总悬浮沉积物的2％。如此高的侵蚀发生率在很长一段时间内无法可持续，因为造成造成的核心尚未挖掘出高级变质岩石，但是自中新世晚期碰撞开始以来，平均侵蚀率与平均历史侵蚀率相当。在随着时间的流逝中，了解在这种环境中驱动侵蚀的是什么是该项目的野心。最终，结果将有助于确定在古代沉积物档案中保留气候和/或构造强迫的影响，并在将来有助于评估气候与构造强迫在地质时期内的重要性与构造强迫的重要性。将记录在先前的河流系统中对挖掘的河流反应，并在使用低温热化学计或地质时钟确定的现代和古代碎屑沉积物中长期侵蚀率。时钟概念可以用作研究岩石首次从深度向表面移动，然后被侵蚀并最终沉积在盆地的基本工具。此处应用的概念是基于以下事实：矿物质因特定温度下特定元素的扩散而封闭。关闭后，时钟开始滴答滴答，并累积了有关样品冷却历史记录的信息。如果已知样品的沉积年龄，即从磁层学或纳米化石中，则可以计算样品通过闭合并从深度中挖出并沉积在盆地中的时间。然后可以通过热建模来推断侵蚀速率。当前的研究往往是模型有偏见或偏置的模型，并且不充分整合。结果，一旦我收集了有关上新世和第四纪序列中有关侵蚀速率的数据，我旨在将表面动态模型儿童应用于对沉积物通量和河流反应建模的长期回应，以应对气候和/或构造变异强迫。该模型结果将产生以紧密反映在沉积物档案中保存的内容，并有助于区分侵蚀记录中的气候和构造强迫。如果实现这一目标，我将提高我们对这些过程如何塑造地球表面的理解，并迈出了将侵蚀历史与沉积物记录联系起来的很大一步。