Short communication: Forward and inverse analytic models relating river long profile to tectonic uplift history, assuming a nonlinear slope–erosion dependency

[摘要] The long profile of rivers is shaped by the tectonichistory that acted on the landscape. Faster uplift produces steeper channelsegments, and knickpoints form in response to changes in the tectonic upliftrates. However, when the fluvial incision depends non-linearly on the riverslope, as commonly expressed with a slope exponent of n ≠1 , the linksbetween tectonic uplift rates and channel profile are complicated by channeldynamics that consume and form river segments. These non-linear dynamicshinder formal attempts to associate the form of channel profiles with thetectonic uplift history. Here, we derive an analytic model that explores asubset of the emergent non-linear dynamics relating to consuming channelsegments and merging knickpoints. We find a criterion for knickpointpreservation and merging, and we develop a forward analytic model that resolvesknickpoints and long profile evolution before and after knickpoint merging.We further develop a linear inverse scheme to infer tectonic uplift historyfrom river profiles when all knickpoints are preserved. Application of theinverse scheme is demonstrated over the main trunks of the Dadu River basinthat drains portions of the east Tibetan Plateau. The model infers twosignificant changes in the relative uplift rate history since the lateMiocene that are compatible with low-temperature thermochronology. Theanalytic derivation and associated models provide a new framework to explorethe links between tectonic uplift history and river profile evolution whenthe erosion rate and local slopes are non-linearly related.

[学科分类] 土壤学