Climate, tectonics or morphology: what signals can we see in drainage basin sediment yields?

Abstract

Abstract. Sediment yields from river basins are typically considered to be controlled by tectonic and climatic drivers. However, climate and tectonics can operate simultaneously and the impact of autogenic processes scrambling or shredding these inputs can make it hard to unpick the role of these drivers from the sedimentary record. Thus an understanding of the relative dominance of climate, tectonics or other processes in the output of sediment from a basin is vital. Here, we use a numerical landscape evolution model (CAESAR) to specifically examine the relative impact of climate change, tectonic uplift (instantaneous and gradual) and basin morphology on sediment yield. Unexpectedly, this shows how the sediment signal from significant rates of uplift (10 m instant or 25 mm a −1 ) may be lost due to internal storage effects within even a small basin. However, the signal from modest increases in rainfall magnitude (10-20 %) can be seen in increases in sediment yield. In addition, in larger basins, tectonic inputs can be significantly diluted by regular delivery from non-uplifted parts of the basin.

The sensitivity of landscape evolution models to spatial and temporal rainfall resolution

“…Downstream, valleys are wider and less steep, with the underlying geology becoming Triassic mudstone and sandstones (Bowes et al, 2003). This basin has been extensively modelled in previous studies (Coulthard and Macklin, 2001;Coulthard and Van de Wiel, 2013;Coulthard et al, 2012bCoulthard et al, , 2013a, and a pre-calibrated version of the CAESAR-Lisflood model was readily available. The basin was sub-divided to provide test subbasins of various sizes, giving three basin sizes -herein referred to as the complete Swale, the Upper Swale and the Arkengarthdale tributary ( Fig.…”

Opportunities from low-resolution modelling of river morphology in remote parts of the world

“…climate variation, hydropower exploitation). Given the lack of detailed and extensive data for remote parts of the world, the simplified model can substitute and/or support multi-parameter 2-D modelling of river watersheds (Coulthard and Van de Wiel, 2013) or be coupled to detailed 2-D modelling of some river features (e.g. junctions and bifurcations), such as the typical downscaling approach used in Guerrero et al (2013b).…”

Quantitative bounds on morphodynamics and implications for reading the sedimentary record

“…1). The latter far exceeds historical records of sediment flux (and its variability), and therefore our understanding of the role of morphodynamic feedbacks in environmental signal preservation is based largely on small-scale physical models 10,15 and numerical experiments 13,[15][16][17][18] . Nonetheless, upscaling results from analogue models to natural depositional systems incorporates uncertainties, and consequently, reconstructions of the sedimentary archives on both the Earth and the Mars routinely neglect any morphodynamic filtering (for example, Zhang et al 7 ).…”

“…Although sedimentary deposits have been shown to contain a rich archive of environmental (allogenic) conditions and their changes 7,13 (that is, tectonics, climatic, sea level, anthropogenic), there is increasing recognition of the role of self-organized (autogenic) dynamics of sediment-transport systems in obscuring or even obliterating the record of externally forced environmental signals [10][11][12]14 . Numerical and physical experiments [10][11][12][14][15][16][17][18] and field investigations 8,19 indicate that the primary signal in physical stratigraphy can in cases be the record of the nonlinear sediment-transport dynamics, played out through geologic time. Detangling autogenic dynamics from allogenic forcing in the sedimentary record is difficult, because we lack quantitative metrics to assess where environmental conditions may be preserved in depositional archives.…”