Minero-petrographical features of weathering profiles in Calabria, southern Italy

The paper reports interdisciplinary research of weathering profile stages on gneiss with regard to tectonic and landscape evolutions of the western Sila Grande Massif (Southern Italy). The outcropping rocks consist of medium- to coarse-grained biotite–garnet and sillimanite gneiss (BGS-G), and medium- to coarse-grained biotite–muscovite migmatitic gneiss (M-G). The BGS-G rocks are fractured and weathered with either massive or foliated texture, whereas the M-G rocks are intensely weathered and fractured with a massive texture and frequent pegmatite veins. Petrographical and mineralogical variations show that both gneissic rocks (BGS-G and M-G samples) underwent weathering processes characterized by a progressive chemical attack on the labile minerals with generation of neoformed minerals and substitution of the original rock fabric. The weathering processes produced phyllosilicates and Fe-oxides; neoformed clay minerals and ferruginous products replaced feldspars and biotite during the most advanced weathering stage. Microfractures and morphological variations occur on the original rock and, thereby, affect the surrounding landscape processes. The weathering profile mineralogy and rock textures viewed in the context of landscape evolution provide useful insights into the widespread slope movement phenomena in the Sila Grande Massif gneiss.

► We examine the different weathering stages on gneissic rocks from Calabria.
► We show in detail changes from fresh to completely weathered rocks.
► We relate weathering profiles with original texture, climate and landscape evolution.
► These results provide a useful tool to gain insight in the landsliding investigation.