The onset of the sedimentary cycle in a mid-latitude upland environment: weathering, pedogenesis and geomorphic processes on plutonic rocks (Sila Massif, Calabria)

This work represents an integrated analysis of weathering landforms, including minor landform morphologies and soil profiles developed on granitoid terrains of the Sila Massif uplands (Calabria, southern Italy). The results of our analysis indicate that cryoclastic and thermoclastic processes, along with chemical weathering, are the main factors controlling rock degradation. Microscale features observed in primary minerals and parent rock fabrics, such as structural discontinuities, cleavage planes, fracturing patterns, and variations in chemical composition, play important roles in triggering weathering and, given sufficient time, progressively lead to grussification and soil development. Exfoliation, hydration, and splitting apart of biotite, as well as hydrolysis and etching of plagioclase and K-feldspar, appear to be prominent factors in the breakdown of bedrock. Whereas time controls the degree of development of the main weathering features and climate influences type and intensity of the dominant processes, relief strongly influences the development and preservation/removal of the regolith/soil cover. Geomorphological evidence of severe surface erosion is quite good, especially along steep slopes where weathering products are quickly removed, although on the highest, dissected paleosurfaces (the oldest paleolandscape remnants in the Sila Massif), wide boulder fields represent relics of past, deep spheroidal weathering that have been exhumed by intense erosion. Erosive, depositional, or reworking phenomena, often enhanced by human activity, are well recorded by macro- and micromorphological features of soils, which show simple, poorly differentiated, rejuvenated profiles, buried or truncated horizons, abundant coarse-grained primary minerals or rock fragments, and pedorelicts. The soil clay mineralogy, characterized by illite, chlorite, and vermiculite, and the dominance of coarse textures confirm a young pedogenetic stage of evolution, although highly weathered sand grains (quartz included) occur in rarely preserved mature paleosols. This interpretation is also consistent with the compositional immaturity of fluvial sands, which have undergone low to moderate transport.