Revisiting morphological relationships of modern source-to-sink segments as a first-order approach to scale ancient sedimentary systems

Abstract

Catchments provide water and sediment to downstream sedimentary systems, and these form individual source-to-sink systems. Source-to-sink systems comprise adjacent linked segments, commonly hinterland catchments, alluvial- and coastal plains, the continental shelf, continental slope and submarine fan. The dimensions of the catchment and how it scales to downstream segments provides insight into the sedimentary and tectonic controls that influence the morphology and sedimentation patterns in a basins evolution. In ancient sedimentary successions, where the sedimentary routing system is buried and inaccessible for study, or fragmented due to uplift and erosion, using scaling relationships can provide a powerful tool to understand the complete sedimentary system.Observational data from modern sedimentary systems provide an opportunity to create morphological and sedimentological scaling relationships of segments on the entire source-to-sink system. However, previous studies on global modern source-to-sink systems have typically been based on a limited number of examples restricted by the data available at the time and the methodology used to analyze large datasets. In the last decade, the volume and quality of remotely sensed information has significantly improved so that it is now timely to revisit scaling relationships of modern source-to-sink systems' segment morphologies, and discuss the implications of those results for sedimentological parameters and applicability to ancient source-to-sink systems.The results of this reanalysis show that dimensions of the catchment and submarine fan segments scale internally in terms of fan width, length and area. In addition, fan area scales to its largest hinterland catchment area in agreement with previous studies, however, it is important to consider all catchments that contribute sediment to a basin floor region. In paleogeographic settings, where individual submarine fans are difficult to tie to a single catchment, and where basin floor systems are amalgamated, the contributing sediment discharge of all catchments may be significant and likely influence the scale of its submarine fan.Accommodation versus sediment supply in relation to relative sea level change are important controls on the position of the shoreline which vary considerably from system to system over time and space, thus influencing morphological relationships between source-to-sink segments. The continental shelf should therefore be viewed as a transient geomorphic feature rather than a segment of a source-to-sink system. Furthermore, the continental slope length should not be used to scale other segments of the source-to-sink system, which contradicts previous research. The underlying tectonic and sedimentological control on the continental shelf and slope segments, in addition to the subjective interpretation of their basinward boundaries, may render those segments unsuitable for scaling the morphology of other segments. The study highlights both the temporal variability and complexity of controls that influence the morphology and scaling relationships of internal and adjacent linked source-to-sink segments, and the need to place this in a framework of both tectonic and sedimentological history.