Conversion of tectonic and climatic forcings into records of sediment supply and provenance

摘要

Understanding how environmental forcings (e.g., tectonics, climate) are transformed by erosional landscapes into sedimentary signals is a critical component of inverting the stratigraphic record. Previous research has largely focused on sediment supply (Qs) and grain size as the de facto sedimentary signals of changing forcing mechanisms. We use a numerical model to consider the paired response of sediment provenance (Pv), expressed as fractional sediment load, and Qs to demonstrate that the same change in environmental forcing may have a different expression in the sedimentary record. While Qs reflects integrated denudation across an erosional catchment, Pv is controlled by spatially variable erosion that occurs in transient landscapes. Pv from proximal sediment sources increases during upstream knickpoint migration, whereas Pv from distal sediment sources increases when bedrock channels incise to produce lower gradient profiles. Differences between the Qs and Pv signals relate to distinct geomorphic processes that operate on different time scales and allow for a refined differentiation of the timing and mechanism of forcings than possible via analysis of either signal alone. Future efforts to integrate multiple sedimentary signals may thus yield a richer picture of underlying forcing mechanisms, facilitating efforts to invert the stratigraphic record.