Forcing controls on sediment generation and erosion rates in the Earth’s highest coastal range: the Sierra Nevada de Santa Marta (NE Colombia)

该项目的目的是研究和量化地球上最高的沿海山脉--内华达山脉的侵蚀率和相关的控制机制。沉积速率和沉积物产量在很大程度上是由构造、气候和岩性等外部强迫控制决定的，这些外部强迫控制反过来又调节着折返作用、水的可用性以及矿物学对机械和化学风化的响应。来自山坡的泥沙的体积、速率和粒度分布代表了从高地地区输送并通过泥沙输送系统传播的泥沙的初始输入。河流沉积物传递了许多信息，反映了每个流域碎屑贡献产生的来源信号，因此比以基岩为重点的其他技术更适合于限制侵蚀速度。然而，与任何其他碎屑方法(例如，沉积物测量、宇宙成因核素和热年代学)一样，使用矿物学数据来估计地貌演变是基于一些假设和限制。位于哥伦比亚加勒比海的圣玛尔塔山脉(SNSM)是一个独特的区域，在那里可以研究和量化在化学风化盛行的活跃构造环境中控制沉积物生成、生产和转移的强迫因素。事实上，高折返速率(&gt；1 mm/年)、热带气候、岩性分布、金字塔形状和随后的径向排水，构成了研究这些因素的相互作用及其在决定沉积物产生、转移和组成方面的作用的理想条件。这项研究旨在利用多学科方法解决地质问题，包括宇宙成因核素、矿物学(大宗岩石学和拉曼重矿物分析)、地球化学和地质年代学等分析工具，并结合高分辨率地貌和构造分析。这套分析技术还保证避免(或至少最大限度地减少)潜在的偏差因素(例如矿物肥力)，这些因素会改变对岩性的正确识别和量化。基本的科学问题集中在(I)每种岩性对构造和气候控制的响应，以及这如何控制沉积物的产生，(Ii)由此产生的河流输送的沉积物成分，(Iii)侵蚀和携带SNSM周围沉积物的水系的形态特征的影响，(Iv)调节每个流域的侵蚀和沉积模式的控制。

The aim of the project is to study and quantify erosion rates and related controlling mechanisms in the Sierra Nevada de Santa Marta, the highest coastal mountain range on Earth. Sedimentation rates and sediment production are largely determined by external forcing controls as tectonics, climate and lithology which in turn regulate exhumation, water availability and mineralogical response to both mechanical and chemical weathering. The volumes, rates and grain size distributions of sediment supplied from hillslopes represent the initial input of sediment delivered from upland areas and propagated through sediment routing systems. River sediments convey a number of information reflecting the provenance signals resulting from detrital contribution of each watershed and are therefore more suitable to constrain erosion rates than other techniques focussing on bedrock. As with any other detrital approach (e.g., sediment gauging, cosmogenic nuclides, and thermochronology), however, the use of mineralogical data to estimate landscape evolution is based on a number of assumptions and limitations. The Sierra Nevada de Santa Marta (SNSM) in the Colombian Caribbean, represent a unique area where to study and quantify the forcing factors regulating sediment generation, production, and transfer in active tectonic settings where chemical weathering prevail. In fact, the combination of high exhumation rates (>1mm/year), the tropical climate, the lithological distribution, the pyramid shape and consequent radial drainage, constitute the ideal conditions for studying the interplay of these factors and their role in determining sediment production, transfer and composition. The research aims at tackling the geological problems using a multidisciplinary approach including analytical tools as cosmogenic nuclides, mineralogy (bulk petrography and Raman heavy mineral analysis), geochemistry and geochronology combined to high-resolution geomorphological and structural analyisis. The suite of analytical techniques also guarantees to avoid (or at least minimise) the potential biasing factors (e.g. mineral fertility) which can alter the correct identification and quantification of contributing lithologies. Fundamental scientific questions focus on (i) the response of each lithology to tectonic and climatic controls and how this controls sediment generation, (ii)the resulting sediment composition delivered by rivers, (iii) the influence of morphological features of drainages eroding and carrying sediments around the SNSM, (iv) the controls regulating erosion and sedimentation patterns for eachdrainage system.