GNGTS 2013 - Atti del 32° Convegno Nazionale

normal faults, mostly dipping towards the E (i.e., an increase of about 2500 m is depicted in AA-AA’ section moving from the hanging wall to the footwall of Mesozoic faults; an increase of about 1800 m is depicted in A-A’ section moving from the hanging wall of the fault trace in the middle part of the section to the footwall of the Travettore-Codevigo fault; Fig. 2). The other sections don’t allow unravel the Mesozoic extension because they parallel the platform margin (B-B’ section) or fall within the Northern Adriatic Basin (CC-CC’, C-C’, D-D’ and E-E’ section). The SVFS partially accommodates also some phases of the Cenozoic flexuring as attested by the thickness variations of the Paleogene to Neogene units, while a control of the eustatism could not be totally neglected (Massari et al., 1986; Mellere et al ., 2000). The Paleocene-Eocene flexuring, linked to the growth of the Dinarides, is recorded only in the eastern side of the foredeep and doesn’t influence the western part (Fantoni et al., 2002). The Chattian-Langhian flexuring of the Veneto-Friuli foredeep is less pronounced and related to the Sothern Alps loading. On the other hand, the subsequent Serravallian-Lower Messinian cycle testifies a prominent flexuring linked to the build up of the Eastern Southern Alps with the development of a deep sedimentary basin (up to 1460 m deep; Fantoni et al ., 2002). Such flexuring is recorded mainly in the central and eastern part of the foredeep and marginally in the study area: an increase of the Upper-Middle Miocene thickness (about 1500 m) is observed only in the A-A’ section moving from W to E with a sharp variation near the faults ( e.g ., the fault depicted in the middle part of the section and the Travettore-Codevigo fault; Fig. 2). The Pliocene-Pleistocene flexural cycle affected only the southern and western part of the foredeep with a bending towards SW linked to the Northern Apennines build up (Fantoni et al ., 2002). The map of the Pliocene base depth (Fig. 3) clearly shows the general deepening of the horizon towards the S, even though a differential slope is observed in the foredeep and between the hanging wall and the footwall of the SVFS. On the other hand, the throw of the Pliocene base along SVFS show a general increase towards NW (from 70 to 430 m along the Conselve-Pomposa and Schio-Vicenza faults; from 60 m to 200 m along the Travettore- Codevigo fault; Tab. 2) with only a small local irregular trend (from 70 m in E-E’ section to 10 m in DD’ section and to 30 m in C-C’; Tab. 1). The two apparently-conflicting results, i.e. the general deepening of the Pliocene base towards the S versus increasing gradient of the post-Miocene fault throws towards the NW, can be reconciled considering the different response of LBE block and the Veneto-Friuli foredeep to the Apennines subduction and the SVFS as a structural boundary between the two domains (inset of Fig. 3). During the Pliocene- Pleistocene, the LBE block was affected by a strong uplift in its northern sector (Zanferrari et al ., 1982) and a deepening in its southern part, as depicted by the Pliocene base map (Fig. 3). Indeed, the area constituted an inherited structural high separating the central-western from the Eastern Southern Alps foredeeps and was free to tilt due to the Apennines subduction. In contrast, the Veneto-Friuli foredeep was already a low area because of the Serravallian- Upper Messinian flexuring associated to the Eastern Southern Alps load (Barbieri et al ., 2004). During the Pliocene-Pleistocene, the foredeep suffered a supplemental southward flexuring with the development of accommodation space filled by Pliocene shallow water sandstones (Eraclea sandstone), grading southward into fine-grained hemipelagic sediments (Santerno group) locally covered by Flysch (Porto Corsini and Porto Garibaldi Formations), and by Pleistocene-Holocene shallow marine sand and sandstone (Asti group) (Mancin et al ., 2009). A differential response of the Veneto foredeep to the Apennines subduction is observed: the southern part was free to bend showing a slope similar to the one of the LBE block (ca. 3%; Fig. 3), while the northern part was unable to uplift due to load of the Eastern Southern Alps margin and was less affected by the bending (slope ca. 1%; Fig. 3). This different Pliocene-Pleistocene behaviour between the two structural domains (LBE block versus Veneto-Friuli foredeep) is recorded along the boundary of the blocks marked by the SVFS. A vertical scissor movement took place on the fault system testified by the increasing throw of the Pliocene base towards NW (Fig. 3). 191 GNGTS 2013 S essione 1.2