Drainage reorganization and divide migration induced by the excavation of the Ebro basin (NE Spain)

Abstract

Abstract. Intracontinental endorheic basins are key elements of source-to-sink systems as they preserve sediments eroded from the surrounding catchments. Drainage reorganization in such a basin in response to changing boundary conditions has strong implications on the sediment routing system and on landscape evolution. The Ebro and Duero basins represent two foreland basins, which developed in response to the growth of surrounding compressional orogens, the Pyrenees and the Cantabrian mountains to the north, the Iberian Ranges to the south, and the Catalan Coastal Range to the east. They were once connected as endorheic basins in the early Oligocene. By the end of the Miocene, new post-orogenic conditions led to the current setting in which the Ebro and Duero basins are flowing in opposite directions, towards the Mediterranean Sea and the Atlantic Ocean. Although these two hydrographic basins recorded a similar history, they are characterized by very different morphologic features. The Ebro basin is highly excavated, whereas relicts of the endorheic stage are very well preserved in the Duero basin. The contrasting morphological preservation of the endorheic stage represents an ideal natural laboratory to study the drivers (internal and/or external) of post-orogenic drainage divide mobility, drainage network, and landscape evolution. To that aim, we use field and map observations and we apply the χ analysis of river profiles along the divide between the Ebro and Duero drainage basins. We show here that the contrasting excavation of the Ebro and Duero basins drives a reorganization of their drainage network through a series of captures, which resulted in the southwestward migration of their main drainage divide. Fluvial captures have a strong impact on drainage areas, fluxes, and their respective incision capacity. We conclude that drainage reorganization driven by the capture of the Duero basin rivers by the Ebro drainage system explains the first-order preservation of endorheic stage remnants in the Duero basin, due to drainage area loss, independently from tectonics and climate.

Neogene Epeirogeny of Iberia

“…A body of work exists that makes use of the stream power erosional model (e.g., slope‐area and “chi” analyses) to predict patterns of fluvial incision, longitudinal profiles, and drainage divide migration across Iberia (e.g., Giachetta et al, ; Vacherat et al, ). We investigate whether an inverse approach that makes use of a simple version of the stream power erosional model and smoothly varying uplift rates can be used to predict meaningful histories of uplift.…”

“…Slope‐area analyses, and increasingly chi‐elevation analyses, are favored methods for solving the stream power model and have been used on drainage networks through Iberia (e.g., Schoenbohm et al, ; Vacherat et al, ; Willett et al, ). However, both approaches have significant drawbacks if one wishes to solve for histories of uplift.…”

Late Pliocene-Pleistocene incision in the Ebro Basin (North Spain)

“…García-Castellanos et al, 2003). The drainage divide delimiting the current Ebro catchment shows numerous evidence of geomorphic disequilibrium suggesting that it is still currently enlarging through drainage network growth, captures, and divide migration (Vacherat et al, 2018;Struth et al, 2019).…”

Base Level and Lithologic Control of Drainage Reorganization in the Sierra de las Planchadas, NW Argentina

“…Additionally, regular transitions from fault‐controlled longitudinal drainage to regional slope‐controlled transverse drainage have been noted in a variety of orogenic settings, such as the northern Andes (Struth et al, ), Pyrenees (Babault et al, ), and Atlas Mountains (Babault et al, ). Drainage reorganization can also fundamentally control the production and preservation of topography; substantial migration of drainage divides (Bonnet, ), the development or excavation of internally drained basins (Sobel et al, ; Vacherat et al, ), the dissection of large plateaus (Giachetta & Willett, ), and the in situ formation of high‐elevation, low‐relief landscapes (Sinclair, ; Whipple et al, ; Yang et al, ) have all been attributed to planform changes in drainage networks and geometry.…”