The Laga Basin: stratigraphic and structural setting

Most of the ancient turbidite systems are known being deposited in foredeep basins<br>at the front of active thrust belt. Differently from fluvio-deltaic systems generally<br>lacated in the more internal portion of these basins, the turbidite systems occur at<br>different depth in the more deeper portions of these basins (foredeep turbidite systems)<br>or in the relatively shallower tectonically confined depressions occurring on top of the<br>thrust belt (wedge-top turbidite systems) (see discussion in Mutti et al. 2002, 2003).<br>Foredeep turbidite systems represent the classical sedimentation in a broad and flat<br>basin plain, showing thick to thin parallel and continuous sandstone beds with the<br>Bouma-type depositional division. Wedge-top turbidite systems are directly fed by<br>fluvio-deltaic systems and more clearly record both climate changes affecting the source<br>areas and tectonic activity of the orogenic wedge.<br>Messinian turbidite deposits of the northern and central Apennines show many<br>characters indicating sedimentation in confined basins, formed since the upper<br>Tortonian in relation to the segmentation of the Langhian-lower Tortonian Marnoso-<br>Arenacea foredeep basin (inner stage of the Marnoso-Arenacea, Ricci Lucchi, 1986). In<br>these last years, detailed facies and physical stratigraphic analyses as a well as structural<br>and thermal analyses, conducted on the Laga and Argilloso-Arenacea Fms (central<br>Apennines), demonstrate as these basins were located at the hinge between foredeep and<br>wedge-top depozones of the Messinian Apennine thrust belt (Milli and Moscatelli,<br>2000, 2001; Bigi et al., 2003; Moscatelli, 2003; Milli et al., 2004; Falcini et al., 2006;<br>Stanzione et al., 2006; Casero and Bigi, 2006; Aldega et al., 2006; Critelli et al., 2007;<br>Milli et al., 2007). Anisotropy of the subducted plate and thrust propagation rate deeply<br>controlled the onset of complex basins at the top of the orogenic wedge (Casero and<br>Bigi 2006; Bigi et al., 2006). The resulting topography of these basins and the<br>concomitant climate changes exerted a strong control on turbidite sedimentation and on<br>the stratigraphic organization of these deposits.