Lithological and structural guidance on speleogenesis in Spluga della Preta cave, Lessini Mountains (Veneto, Italy)

Spluga della Preta is one of the first caves in Italy to be well studied and described from a geological and morphological point of view. Eighty years after its first exploration a large amount of lithological and structural data has been collected in the whole karst system and detailed surface geological surveys were carried out. The step-like profile of the cave was initially considered as a consequence of base-level lowering stages related to the entrenchment of the nearby Adige River. In this work lithological guidance of the horizontal levels is demonstrated, considering only the deepest passages to be palaeo-phreatic. The main tectonic structures guide the oldest and inactive parts of the cave, developed mostly within weakly cohesive fault breccias, whereas the active streams are now deepened along secondary joints. Morphological analysis allows inference of a hypothesis concerning the speleogenetic evolution of the cave and its relationship with an upper perched aquifer hosted in the Cretaceous Maiolica Formation.