The Dolenjska Karst Area Uncovered on the Bič–Korenitka Motorway Section

Abstract

Limestone along the Bič–Korenitka motorway route is tectonically heavily fractured, forming broad collapsed and crushed zones, where it is often fractured to the level of tectonic breccia. This is understandable, as the area in question is part of the Sava compressive wedge which has undergone several phases of tectonic processes. Unlike southwestern Slovenia, where Cretaceous limestone prevails, this karst developed in the Triassic and Jurassic limestone which is covered with thicker weathered material. The most prominent karst formations are sinkholes which can be found at the bottom of uvalas. In the course of the motorway construction work, subsoil karren and caves were also uncovered. Those that developed at the bottom of the lowlands and are often flooded by underground streams are of exceptional shapes. They feature a unique rock relief which is now being described for the very first time. The old caves, through which streams were once flowing, attest to the lowering of the groundwater level, which reaches the surface only in the lowest-lying lowlands. A good part of the caves is filled with fine-grained sediment and has been transformed underneath it. The shaping of fissure caves located predominantly along vertical cracks could be defined as having occurred subterraneously. The water widened the cracks into fissure caves and at the same time filled them with fine-grained sediment. The characteristics of the shallow (underground water is close to the surface), sediment-covered, specific type of Slovenian karst are in the process of being brought to light. Many of them (caves, subsoil karren or stone forests) are worth being protected and preserved.