The S2 foliation is affected by later open to tight folds (F3 and F4). F3 folds have sub-vertical axial planes and mainly NW-SE trending axes and a poorly developed axial plane crenulation cleavage. In the Anglona region the F3 fold axes show a NNW-SSE trend plunging 20-25° toward north (Fig. 4). These folds are mainly caused by a nearly N-S continuing compression during or soon after the main transpressive deformation event (D2). The F3 folds show an axial trend weakly deviating from the F2 axes folds and to L2 stretching lineation (Figs. 4a and b). Analogously to F2 folds the F3 folds are more developed towards the N-NE. In Asinara island, moving northward, up to the Stretti zone, the F2 fold axes are weakly affected by F3 folds that show a more regular trend of N90-100° plunging 35-40° to both the NE and SW (Fig. 4 a).
In both the Nurra-Asinara island and the Anglona-SW Gallura zones, the F3 folds produce interference pattern of both the type 0 and 3 (Ramsay & Huber, 1987). F4 have kink geometry with relatively steeply dipping axial plane. Their axes show variable trends and plunges in the different areas (Fig. 4). Rare recumbent folds have been observed with sub-horizontal or shallowly dipping axial planes (Fig. 9). They are associated with shallowly dipping normal shear planes with a broadly top-to-the south sense of shear, with development of cataclasites and asymmetric folds. Top-down to the south ductile/brittle to brittle shear zones and folds with horizontal axial plane accommodate the extensional collapse of the belt at upper crustal levels, after the thickening stage (Carmignani et al., 1994).