DRAINAGE AREA EXCHANGE BETWEEN RIVER BASINS PRODUCES LONG-LIVED TRANSIENT LANDSCAPES

Cratonic landscapes make up the majority of Earth’s surface and contribute significant quantities of sediment to ocean basins. Previous research on cratonic landscapes has pointed to diverse drivers of relief and rates of erosion in individual river basins, leaving the processes that set the first-order relief structure of tectonically quiescent landscapes poorly constrained. Here we show that erosional competition between river basins may control large-scale morphology in some cratonic landscapes. We use topographic analysis, catchment-averaged denudation rates determined from concentrations of ¹⁰Be in modern river sand, and a proxy for the steady-state elevation of river networks, χ, to demonstrate that river basin dynamics, including divide migration and stream capture, drive much of the observed variability in erosion rates and topographic asymmetry in the Ozark dome, a low-elevation, cratonic landscape.

We find that high-elevation, low-relief surfaces, often interpreted as relict surfaces, can form in situ as a result of basin dynamics. The positive feedback associated with persistent loss of drainage area has resulted in basins with long-term erosion rates that are lower than the surrounding landscape and lower than the rate of uplift. These basins have thus lost relief and increased in elevation. The stream-power river incision model predicts landscape response times on the order of 10 Ma, suggesting that landscapes subjected to consistent, low rates of isostatic uplift should be close to steady state after ~ 10 Ma. The Ozarks have not experienced significant tectonic activity since the late Paleozoic, yet, we find that rivers draining the Ozark dome are in geometric disequilibrium and are actively reorganizing. Our results suggest that the persistent exchange of drainage area between adjoining river basins and the concomitant nonuniformity in erosion rates can greatly increase the time-to-steady-state and is a viable mechanism to autogenically produce long-lived transient landscapes.