Erosive Response of Non-Glaciated Pyrenean Headwater Catchments to the Last Major Climate Transition and Establishing Interglacial Conditions

Kurt Martin Stange,Hans-Joachim Kuss,Cornelia Spiegel,Johan Petter Nystuen,Reza Sohbati,Ivar Midtkandal,Warren Thompson,Andrew Murray

doi:10.3390/quat2020017

Abstract

Non-glaciated mountain headwater catchments feature high-resolution geomorphic archives, which provide important insight into erosive processes and sediment dynamics in mountain ranges. As such the Valle de la Fueva catchments in the southern Pyrenees present high-lying talus remnants, extensive denudation surfaces (pediments), deeply incised tributary ravines, and low-lying fluvial-cut terraces. Based on geomorphic analyses and absolute dating using terrestrial cosmogenic nuclides and optically stimulated luminescence, a (late stage) catchment erosion model for the Valle de la Fueva was elaborated and indicates successive development stages of (i) lasting pedimentation under cold-climate conditions during Marine Isotope Stages 4–2, (ii) rapid fluvial dissection, sediment remobilization and downcutting of ravines in response to the last major climate transition and establishing interglacial conditions, and (iii) late stage fluvial incision after 3–4 ka due to regionally increased flood magnitudes, and/or intensification of agriculture and forest management. Valle de la Fueva headwater catchment analysis indicated that the styles and magnitudes of basin surface processes were directly correlated with the amplitude and nature of paleoclimatic changes, modified by the interplay of environmental parameters. In contrast to large-scale fluvial systems, mountain headwater catchments seemed to be less afflicted with temporal and spatial averaging biases. They are thus useful targets for investigating direct climate change effects, surface process coupling, and non-linear response mechanisms in Quaternary fluvial systems.

Highlights

A great deal of research has been carried out on the long-term evolution of drainage networks and for understanding the coupling and feedback mechanisms between climate, tectonics, fluvial system dynamics, and surface processes in general; e.g., [1,2,3,4,5,6,7,8,9,10]
In extension to Stange et al [18], this paper presents catchment erosion rates, volumetric measurements and sediment budgets, as well as new terrestrial cosmogenic nuclide (TCN)- and optically stimulated luminescence (OSL)-derived chronological data for the most recent fluvial erosion phase in the Valle de la Fueva headwater catchments in the southern central Pyrenees (Figure 1)
Similar conclusions could be drawn from clast 3305-05 top (Table 4; location 4, Figure 2), which was last exposed to daylight at 96 ± 7 ka, around the onset of the last cold climate cycle

Summary

Introduction

A great deal of research has been carried out on the long-term evolution of drainage networks and for understanding the coupling and feedback mechanisms between climate, tectonics, fluvial system dynamics, and surface processes in general; e.g., [1,2,3,4,5,6,7,8,9,10]. Long-term fluvial incision rates derived from the vertical spacing of terrace staircase systems are potentially misleading as to the actual magnitudes of paleo-surface processes. This is because erosion rates that are calculated from vertical (i.e., two-dimensional) incision scarps between adjacent terrace features are potentially afflicted with spatial- and time-averaging biases—the latter of which increases with the age of terraces. This includes potential time lags, for instance, between glacial headwater dynamics and downstream fluvial response

Methods

Results

Discussion

Conclusion