Composition of modern stream sands derived from sedimentary source rocks in a temperate climate (Northern Apennines, Italy)

The Northern Apennine is a moderate relief thrust–fold belt (maximum elevation of less than 2000 m above sea level) lying in an area of temperate climate, drained by short (mean 50 km) transversal streams flowing northwards into the Po River main channel. The mountain range is mostly made-up of sedimentary rocks with minor ophiolite slices. The source rock types of nine contiguous watersheds, draining an overall area of more than 2800 km2, were quantitatively defined through a Geographical Information System (GIS). The bedrock lithology at the source area was compared with the composition of the medium-sized fluvial sand to evaluate how the various types of sedimentary source rocks are represented in the stream sand population. The sand provenance approach has two approximation levels; the first level distinguishes the source rock types and constrains some assumptions about the degree of recycling; the second level calculates the contribution of different source rock types according to the previous results. Provenance modelling obtained through this method fits well with the real geology of the eroded landscape. This provides an actualistic example that can be useful for a quantitative provenance approach to the study of ancient sediments fed by recycled sedimentary thrust–fold belts.