The Quarternary Development of the Škofja Loka Hills

Abstract

The study deals with the geomorphological development of the Škofja Loka Hills (the area along the Sora river, between the Ljubljana Basin and the Idrijca river) during the Quarternary. After the formation of broad Tertiary tropic planation surfaces and of two broad lower terraces lying directly beneath them that can be established in limestone and in impermeable rocks, an erosion into depth followed which created valleys 150—300m deep. In these narrow valleys, which become wider only in the non-limestone impermeable rocks, six narrow, yet very distinct, terraces have been preserved. The author atributes of these terraces the Ice Age origin, taking into consideration the state of their preservation along all these valleys, the exceptional thickness and characteristic rounding of the gravel and its connection with the periglacial fine scree material, with the glaciofluvial gravel and moraines, as well as with the locally preserved pollen deriving from the cold periods. During the Quarternary the erosion was a very continuous process. It is supposed to have coirtdiiued from the warmer periods into the older ones, when there was besides the erosion into depth also an intensive lateral erosion. This process was discontinued only during the driest olimaxes of the glaciation periods when the rivers could no longer carry away all the fine scree material from the valleys which had glided into them by way of solifluction. The fine scree material was thus left in the valleys and this considerably diminished the accumulative capacity of the Sora river at its entrance from the hilly region into the Ljubljana Basin. For this reason its predominantly fluvioperiglacial alluvion was covered by the alluvion brought by the Sava river which had carried from under the glaciers enormous quantities of the glaciofluvial gravel. During the glaciation periods a very effective headwards erosion and the corresponding recession of slopes had also taken place. This is proved by the exceptionally wide funnel-shaped headwaters areas of the valleys, and above all by the periglacial fine scree material preserved in the lower part of these slopes and in the alluvial fans under them which originates mainly from the last Ice Age.