The Waidbruck conglomerate forms a formation consisting of clastic sedimentary rocks , which is superimposed on the crystalline basement and merges upward into the volcanic rocks of the Etschtal volcanic group . It is the deposition of rivers and streams. The formation is therefore not continuously present, but only formed locally. In addition to the occurrences near Waidbruck in Eisack Valley, there are also larger occurrences in Valsugana . The conglomerate is dated to the early Permian , more precisely to the sacmarium . So it was formed between 294.6 and 284.4 million years ago. In profile near Waidbruck, the conglomerate is 50 meters thick, and overall the thickness in the western Dolomites varies between 0 and 150 meters.
These are poorly sorted conglomerates and gravel-bearing sandstones. The pebbles are usually only slightly rounded, which suggests a relatively short transport route. Sandstone layers increase somewhat towards the top. While crystalline basement rock has been worked up in the lower layers, phyllite pebbles from Brixen quartz phyllite and quartz pebbles can be found at Waidbruck, and volcanoclastic parts increase in the upper part and form a smooth transition to the volcanites of the Etschtal volcanic group. In the classic outcrop near Waidbruck there is a color change from red conglomerates in the lower area to gray sediments in the upper area. The reddish sediments indicate formation in a desert climate, the gray sediments indicate a more regular water flow.
The sediments at the base are interpreted as debris flows with subsequent short transport in a periodically water-bearing torrent. The overlying sediments could represent sediments from alluvial fans or molasses sediments in fracture tectonic depressions in a hilly or mountainous country.
- Commissione Italiana di Stratigrafia: Arenaria di Val Gardena , page 61. PDF file