Abstract
In tectonically active mountain ranges, the landscape is shaped by the interplay of erosion/sedimentation and tectonically driven crustal deformation. Characteristic landforms such as moraines, wind gaps, fault scarps, and river terraces can be used to decipher the landscape evolution. However, the available data often allow for different interpretations. Here we study the Pradol (Pradolino) Valley in Western Slovenia, a deeply incised canyon whose floor rests several hundreds of metres above the surrounding valleys. We use high-resolution digital elevation models, geomorphic indices and field observations to unravel the evolution of this peculiar landform. We present a six-stage evolution model of the canyon that includes the blockage of valleys by advancing glaciers, river diversion, and rapid incision due to a high discharge of post-glacial meltwater. The formation of the Pradol Valley was most likely facilitated by an underlying fault that serves as an easily erodible weakness zone in the Mesozoic limestones. Our model indicates that the formation of the canyon could have occurred during the last glaciation, which results in incision rates of several cm/yr. With the proposed model we can explain all remote and field observations available. Our study shows that a complex interplay of different landscape-shaping processes is needed to explain the occurrence of the Pradol dry valley and that rapid changes in the morphology occurred after the last glacial maximum.
Highlights
IntroductionIn the following we only use the Slovenian names) is a wind gap located close to the village of Logje at the Slovenian-into the valley between Mija and Matajur (Italian) border, approximately 12 km west of Kobarid (Fig. 1)
We conclude that the Pradol Valley must have had a major episode of incision during the last glacial maximum (LGM), lasting ca. 7-15 kyr due to the blocking of the Nadiža channel by glaciers coming from NE
Cataclastic abrasive wear of the bedrock caused by faulting along the Predjama Fault located along-strike the canyon likely contributed to this process
Summary
In the following we only use the Slovenian names) is a wind gap located close to the village of Logje at the Slovenian-Italian border, approximately 12 km west of Kobarid (Fig. 1). It is a steep canyon with vertical to overhanging walls, bisecting the mountain ridge of the Vogel (Italian: Monte Voglu; 1124 m) and the Mija (Italian: Monte Mia; 1237 m). This study aims to provide an insight into the formation process of the Pradol Valley from a geomorphological perspective. We constrain the role of major landscape forming processes, such as active tectonic deformation, glaciations, and fluvial erosion on the formation of the valley and the surrounding region and present a model that fits all available observations
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