Understanding sedimentary processes in the uphill catchment of Source-to Sink-Systems: An example from the Sierra Nevada de Santa Marta (NE Colombia)

The character of sediments generated in the uphill catchments is markedly variable and exert a primary control on the sediment cascade and the evolution of source-to-sink systems. Understanding these processes is therefore critical to better understand how these systems function in both modern and deep-time settigns. This study aims to understand and quantify the processes regulating sediment generation and transfert in the uphill catchments of the Sierra Nevada de Santa Marta (SNSM) - the world's highest coastal range within subtropical regions. We tackle the complex task of quantify the role of external forcings on sediment production in 17 drainages basins within the SNSM by challenging conventional assumptions and introducing new compositional models. Our research significantly expands the existing knowledge base on compositional modelling by presenting a systematic framework for characterizing sediment generation, particularly focusing on the influence of tectonics, climate, lithological factors, and analytical reliability. We produced a robust compositional database encompassing optical petrography (11,463 grains), Raman heavy mineral analysis (44,782 grains), detrital geochronology (apatite, titanite, and zircon – 6378 grains), apatite (1159 grains) and titanite (1571 grains) geochemistry, and bulk-rock and silt-clay geochemistry.We present a novel linear log-ratio (end-member) sediment generation model calibrated on geomorphological parameters as connectivity and erodibility, facilitating the evaluation of sediment generation capacities from metamorphic, plutonic, and volcanic lithologies. Sediment texture and composition vary remarkably from drainage to drainage, providing the elements to model both the relative (by comparing lithologies) and absolute capacity of drainage lithologies to produce sediments, in the settings of the SNSM. Our results reveal significant variations in sediment texture and composition among drainages, providing insights into both the relative and absolute capacity of different lithologies to produce sediments in the SNSM setting. We found that metamorphic rocks produce higher amounts of sand compared to plutonic and volcanic lithologies, while the sediment generation capacity of plutonic rocks is up to 9 times higher than that of volcanic lithologies. In mixed drainages with equal proportions of metamorphic and other rocks, metamorphic detritus can constitute up to 60 % of sand compositions. Surprisingly, geomorphological parameters like structural connectivity and erodibility played a minor role in sediment generation in this tectonic setting, contrary to findings in other regions. This study underscores the importance of understanding processes operating in uphill catchments to better constrain those acting in other sectors of Source-to-Sink systems. Our findings contribute to advancing quantitative methods in provenance analysis and improve our understanding of sediment generation and routing in complex tectonic and climatic settings.