An alternative method of azimuthal data analysis to improve the study of relationships between tectonics and drainage networks: examples from southern Italy

The Auletta basin coincides with the present-day lower valley of the Tanagro River and is filled by upper Pliocene to lower-middle Pleistocene marine to continental sediments. Such deposits are tilted towards SW and dislocated by the 20 km-long NW-SE-trending fault bordering the huge carbonate morphostructure of the Alburni Mts. The complex evolution of the basin during the Quaternary has controlled the geometric arrangement of the main rivers of the area. The two major streams (i.e. Tanagro and Bianco rivers) appear to be structurally controlled by N120-140 degrees-striking faults, as suggested by morphometric and geometrical (i.e. right-angled confluences and elbows, trellis-type fluvial pattern) characters of the net. In the southern flank of the valley, the preferred orientation of the I and II order fluvial channels (orthogonal to the Alburni Mts) indicates that the high relief and steep slopes of the Alburni positive morphostructure have been able to reduce the influence of the bedrock fracture pattern on the arrangement of minor streams.

A detailed morphotectonic study of two intermontane basins located in the axial zone of the southern Apennines (Auletta and Valico di Prestieri basins) has been carried out to assess the relationships between Quaternary tectonics and fluvial network geometry. The comparison of morphological and structural features has been aided by an alternative method of morphotectonic data analysis based on the treatment of azimuthal populations by cumulative diagrams.