I conglomerati prewürmiani della conca di Ponte nelle Alpi (Belluno)

The pre-würmian conglomerates of the Ponte nelle Alpi zone (Belluno, Northern Italy)

Abstract

This report describes and maps the pre-würmian conglomerates which outcrop on the bottom of the Ponte nelle Alpi zone. The authors’ research reveals new elements which are useful in explaining the sedimentation conditions which caused those irregularities in stratification already partly reported by previous Authors. On the basis of the data contained in the literature and field observations, the chronostratigraphic collocation of these conglomerates is discussed, also taking into account those of S. Giorgio (reported here for the first time) which modify existing official maps. The conglomerates of the Ponte nelle Alpi zone show similar characteristics and belong to a single sedimentary complex, laid down in at least two depositional phases, clearly distinguishable both at Cadola and at Prà d’Anta. The lower part of these deposits shows the typical sedimentation irregularity of the ice contact drifts, while the upper part is of fluvio-glacial origin. The anomalous disposition of the conglomerates at Cadola, concordant with the Eocene p.p. marles of the rocky substrate, gives rise to the hypothesis that their dislocation took place due to neotectonic phenomena which also involved the slope on which they lie.