Combining information preserved in fluvial topography and strath terraces to extract rock uplift rates in the Apennines

Abstract:

Longitudinal river profiles respond to changes in tectonic uplift rates through climate-modulated erosion. Therefore, rock uplift rate information should be recorded in fluvial topography and extracting this information provides crucial constraints on tectonic processes. In addition to the shape of the modern river profile, paleo-river profiles can often be mapped in the field by connecting strath terraces. These strath terraces act as markers that record complex incision histories in response to rock uplift rates that vary in space and time. We exploit an analytical linear solution to the linear version (n=1) of the stream-power equation to efficiently extract uplift histories from river networks and strath terraces. The analytical solution is based on the transient solution to the linear version (n=1) of the stream-power equation. The general solution to this problem states that the elevation of a point in a river channel is equal to the time integral of its uplift history, where integration is carried out over the time required for an uplift signal to propagate from the baselevel of the river network to the point of interest. A similar expression can be written for each strath terrace in the dataset. Through discretization of these expressions into discrete timesteps and spatial nodes, a linear system of equations can be solved using linear inverse methods. In this way, strath terraces and river profiles can be interpreted in an internally consistent framework, without the requirement that the river profile is in a steady state. We apply our approach to the Northern Apennines where strath terraces have been extensively mapped and dated. Comparison of our inferred rock uplift rate history with modern rock uplift rates enables us to distinguish short-term deformation on a buried thrust fault with long-term mountain building processes.