- Copyright © 2016, SEPM (Society for Sedimentary Geology)
Production, transport, and deposition of siliciclastic sediments takes place across changing altitudes, physical processes, environments, and controls en route from source to sink commonly through a downstream narrowing and then broadening fairway of sediment grains, constituting giant “hourglasses” of nature, a fundamental unit of both geomorphology and sedimentology.
Here we review the status of the rapidly evolving multidisciplinary source-to-sink approach, and compare it with the more mature sequence stratigraphic approach. The latter uses outcrop, well, and seismic data to gain information about elements of basin fills with less data coverage and is thus mainly a “sink-to-sink” approach. Source-to-sink on the other hand aims to understand the dynamics and budgets of the complete onshore–offshore sediment fairway, including elements of the transect that are no longer preserved. Furthermore, we summarize the spatial and temporal variability of source-to-sink systems, and discuss qualitative and semiquantitative methods for reconstruction of area, relief, and sediment supply from source terrains.
The variability of source-to-sink systems is viewed in the framework of three end-member types, “steep, short, and deep,” “wide and deep,” and “wide and shallow,” where each is characterized by typical patterns of sediment partitioning and long-term preservation. Modern and sub-modern systems are keys to enhance our understanding of their ancient counterparts. Three different time-framework categories for source-to-sink analysis are presented: modern systems, pre-modern Quaternary systems, and pre-Quaternary systems, all of which have large differences when it comes to amount and type of data, controlling factors, accuracy in interpretation, and societal applications. Importantly, systems are evolving through time with the effect that estimations of source-area parameters for one period of time may change significantly into another when boundary conditions are different.
Sink reconstruction can, with variable confidence, be established through the use of seismic-reflection, well, and outcrop data, whereas reconstruction of source relief, drainage, and sediment production is a more challenging task. Methods like landscape interpolation, sediment volume backfilling, geomorphological scaling relationships, sediment-load estimations from river data and from stratigraphy as well as geochemical data can, preferably in combination, be used to unravel past source terrains. These methods are presented along with a discussion on how they can improve models for basin fill.
Sink and source reconstruction is a two-way process. Source reconstruction sheds light on sink understanding and vice versa. This integrated approach is a prerequisite for further advance in source-to-sink studies. The prognosis of source-area parameters may give additional insight into the complete erosional–depositional system in general and sediment supply in particular and hence enables us to arrive at more robust models and predictions for the sink where resources commonly are contained.