1 Seismic images of an extensional basin, generated at the hangingwall of a 2 low-angle normal fault: the case of the Sansepolcro basin (Central Italy) 3 4 Massimiliano R.Barchi (1) & Maria Grazia Ciaccio* (2) 5 (1) University of Perugia, Italy, Dpt. Scienze della Terra, Perugia, Italy 6 Fax +39 075 5867167 7 e-mail
[email protected] 8 (2) Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy 9 Fax +39 06 51860307 10 e-mail
[email protected] 11 12 13 Abstract 14 15 The study of syntectonic basins, generated at the hanging-wall of regional low- 16 angle detachments, can help to gain a better knowledge of these important and 17 mechanically controversial extensional structures, constraining their kinematics and 18 timing of activity. 19 Seismic reflection images constrain the geometry and internal structure of the 20 Sansepolcro Basin (the northernmost portion of the High Tiber Valley). This basin 21 was generated at the hangingwall of the Altotiberina Fault (AtF), an E-dipping low- 22 angle normal fault, active at least since Late Pliocene, affecting the upper crust of 23 this portion of the Northern Apennines. 24 The dataset analysed consists of 5 seismic reflection lines acquired in the 80s’ by 25 ENI-Agip for oil exploration and a portion of the NVR deep CROP03 profile. The 26 interpretation of the seismic profiles provides a 3-D reconstruction of the basin’s 27 shape and of the sedimentary succession infilling the basin. This consisting of up to 28 1200 m of fluvial and lacustrine sediments: this succession is much thicker and 29 possibly older than previously hypothesised.