Kaltbach Cave (Siebenhengste, Switzerland): Phantom of the Sandstone?

Abstract

Jama Kaltbach je razvita v Hochgantskem eocenskem peščenjaku na območju Siebenghengste v Švici. Rezultat ponovne izmere jame je precej večja dolžina, nov načrt jame in številna opažanja, ki kažejo na to, da jama ni nastala z »normalno speleogenezo«, ampak je t.i. fantomska jama. Fantomske jame nastajajo pri delnem preperevanju nečistega apnenca v toplih klimah, v pogojih nizkega hidravličnega gradienta. Ob povečanju gradienta, voda izpere netopni preostanek, pri čemer nastane jama. Članek obravnava geomorfološke značilnosti jam, ki nam omogočajo prepoznavati fantomske jame.

Kaltbach cave is developed within the Eocene Hohgant sandstone in the Siebenhengste area in Switzerland. A remapping project of the cave resulted in a huge increase in length. It also produced a complete, updated map and longitudinal section. The cave’s morphology does not fitwiththe“normal”speleogenesis:itisaso-calledphantom cave. Phantoms are created by differential weathering of impure limestone under a preferably warm climate and a very low hydrologic gradient. Once the gradient steepens, the undissolved residual sediments are piped out; the “cave” manifests itself. The paper discusses the geomorphological features that permit to recognize the phantom caves.