RESTRICTED RIFTING AND ITS COEXISTENCE WITH COMPRESSIONAL STRUCTURES - RESULTS FROM THE CROP-3 TRAVERSE (NORTHERN APENNINES, ITALY)

A geological interpretation of the deep seismic reflection line CROP 3 (Italian program CROsta Profonda: deep crust, profile no. 3), which c rosscuts the Northern Apennines from the Tyhrrenian to the Adriatic co ast, is presented. The profile images the lithosphere up to 15 s TWT a nd highlights several peculiarities: (a) the lower crust is bedded by discontinuous sub parallel reflective markers which terminate at appro ximate to 7 s beneath the western side of the profile; (b) in the same area a notable reflection is recognizable at 10 s and is interpreted as the top of the asthenosphere; tc) east-plunging shear zones are rec ognizable throughout the crust, By contrast, the Adriatic (outer) side of this line shows: (a) reflections deepening westward, from 13 to 15 s TWT, related to the base of the crust (33-38 km depth); (b) the abs ence of thick bedding of reflective markers within the lower crust; an d tc) tectonic structures affecting the basement which are different f rom those which deform the cover of the Northern Apennines, Geological interpretation is based on the eastward migration of ductile shear zo nes which have been recognized on the seismic line. The bending of the outer zone crust is considered to be a consequence of the rifting pro cess with the application of pushing forces against the Adriatic litho sphere which cannot escape toward east.