Deciphering Earth's natural hourglasses: Perspectives on source-to-sink analysis

Production, transport and deposition of sediments takes place across changing altitudes, physical processes, environments and controls en route from source to sink through a downstream narrowing and then broadening fairway of... [ view full abstract ]

Production, transport and deposition of sediments takes place across changing altitudes, physical processes, environments and controls en route from source to sink through a downstream narrowing and then broadening fairway of sediment grains, constituting giant “hour-glasses” of nature, a fundamental unit of both geomorphology and sedimentology.

Here we review the status of the rapidly evolving multidisciplinary source-to-sink approach, compare it with the more mature “sink-to-sink” sequence stratigraphic approach, summarize the spatial and temporal variability of source-to-sink systems, and discuss qualitative and semi-quantitative 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 active margins, passive margins and intra-cratonic basins, of which each is characterized by typical patterns of sediment partitioning and long term preservation. The systems are largely time invariable; 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; sub-modern to 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, well and outcrop data, whereas reconstruction of source relief, drainage and sediment production generally is attached with more uncertainty. Methods like landscape interpolation, sediment volume backfilling, geomorphological scaling relationships, sediment flux estimations from river data and from stratigraphy as well as isotope-based analytical data can, preferentially in combination, be used to unravel past source terrains. Such 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 mutuality 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 were resources commonly are contained.