Guidebook - Ispra

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Volume n° 3 - from P14 to P36 P18 P18 - Leaders: M.Morsilli, G. Rusciadelli, A. Bosellini Figure 2.3.3 - Reconstructed geometry of the pre-collapse depositional profi le of the Maiella platform at the end of the Early Cretaceous. Following this reconstruction, the pre-collapse depositional profi le corresponds to a depositional and essentially aggrading or weakly prograding platform with a slope inclined about 25-30°. slope clinostratifi ed deposits) (Rusciadelli et al., 2003), and the pre-collapse depositional profi le of the platform-to-basin transition can be envisaged (Figure2.3.3). The reconstruction of the possible precollapse depositional profi le of the Maiella platform margin at the end of the Early Cretaceous suggests that the platform edge extended 1 km further to the north, compared with the present position of the paleoescarpment. The maximum thickness of the sediments eroded by the margin collapse is estimated around 300 m (Rusciadelli et al., 2003). The presence of large and small-scale scalloped structures and of breccias and megabreccias deposits, intercalated in slope successions during two distinct time intervals, suggests that the present escarpment confi guration was the result of two main evolution phases dominated by collapse events (Figure2.3.4). The fi rst one occurred between the Middle Albian and the Lower Cenomanian, as suggested by the age of megabreccias with platform derived clasts outcropping northward (Bocca di Valle unit), and is defi ned by a major collapse event which affected the platform margin along its whole length. The previous physiography of the margin was deeply modifi ed, and for the fi rst time during the Cretaceous the platform to basin transition corresponds to an erosive and by-pass slope. The inherited confi guration was characterised by prominent ridges with an average 30° dipping stable slope, and by indentations with a less stable slope, affected by periodic different-scale collapses. These were responsible for the progressive backstepping of the platform edge. During this phase, large amounts of breccias, megabreccias and bioclastic deposits were shed basinward over distances of 15 km as average from the platform edge and distributed over an area of 150 km 2 at least. Concomitantly to this phase, or immediately after, a widespread emersion of the platform occurred followed by
THE APULIA CARBONATE PLATFORM-MARGIN AND SLOPE, LATE JURASSIC TO EOCENE OF THE MAIELLA MT. AND GARGANO PROMONTORY: PHYSICAL STRATIGRAPHY AND ARCHITECTURE P18 Figure 2.3.4 - Interpretation of the origin and evolution of the Maiella paleoescarpment during the Albian p.p.- Campanian p.p. time interval (after Morsilli et al., 2002). 25 - P18 Volume n° 3 - from P14 to P36
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