L’analisi geomorfica quantitativa applicata allo studio morfotettonico dell’Alta Garfagnana e della Lunigiana Orientale (Appennino Settentrionale)

The quantitative geomorphic analysis applied to the morphotectonic study of the High Garfagnana and Eastern Lunigiana areas (Northern Apennines, Italy)

Abstract

In a sector of the Northern Apennines corresponding to the area between the two tectonic depressions of the High Garfagnana and the Lunigiana some techniques of quantitative geomorphological analysis were applied with the aim of characterising the morphostructural features of the area. The importance that this particular region has in the tectonic evolution is associated with the interaction between the lifting processes of the core complex of the Apuan Alps and the neighbouring graben separated by a displacement with complex structural characteristics. Calculations of the extensive parameters of the hydrographic network and relief, such as drainage density and relief energy, were associated with the determination of morphometric parameters of the hierarchized hydrographic system on an area of more than 400 km². The existing relationship between development of the hydrographic network and the fracturing systems was deducted from the azimuthal analysis of the fluvial segments divided into the hierarchical order and the relative basins. Analysis of the quantitative data interpreted in areal and linear morphostructural terms showed both the sectorial disequilibria of the differential upliftings and also the chronological variations of the systems of fragile deformation starting from the Middle Pliocene. An E-W system at present constitutes both the main direction of the shear with dextral mechanism between the two graben and also the northern limit of the Apuan dome, which represents the area with the most rapid uplifting. Progressive anti-clockwise rotations of the azimuthal directions should indicate an analogous rotation of the axis of maximum extension at least until the Lower Pleistocene. Alignments that are significant, but not of univocal interpretation within the present tectonic context, are represented by the ENE-WSW and ESE-WNW directions.