History and tectonic implications of low‐angle detachment faults and orogen parallel extension, Picentini Mountains, Southern Apennines fold and thrust belt, Italy

Abstract

Abstract. Late Miocene to Pliocene movement on low-angle extensional faults within the internal Southern Apennines orogenic belt was superposed on an earlier, Miocene imbricate thrust stack. The low-angle faults formed within the interior of the belt during orogen parallel extension as thrust imbrication continued in the foreland. Extreme tectonic thinning defines discrete structural domains of hyperextension which are linked by a complex system of extensional and transcurrent faults. Some of the best examples of hyperextension structures in the Southern Apennines are exposed in the Picentini Mountains. In this area, detailed mapping, fault-kinematic analysis, and excellent stratigraphic control contributed to the construction of restorable cross sections and forward models of deformation.With these constraints, it is possible to document extensional displacement on shallowly dipping supercrustal faults whose orientation is a primary feature and is not due to later tilting. During movement, upper plate rocks were disarticulated by listric and planar normal faults that soled into a ramp-flat detachment system. The depth of the basal detachment increased in the direction of upper-plate motion and ranged from 5 to 10 km. Displacement on the low-angle detachment was accompanied by block tilting in the upper plate assemblage, incisement and excisement of the upper and lower plate rocks as fault trajectories changed through time, and the progressive cataclasis of hanging wall and footwall assemblages. Preexisting thrusts were only locally reactivated during extension, and faults emanating from the underlying decollement systems cross the imbricated thrust sheets at moderate to high angles. Longitudinal extension resulted in thinning of the thrust stack to less than half the original thickness and had a cumulative magnitude of between 200 and 250 % (beta > 2).

The Campania‐Lucania Extensional Fault System, southern Italy: A suggestion for a uniform model of active extension in the Italian Apennines

“…The Picentini detachment appears, in its western part (Monte Stella–Monte Monna zones), as a clearly inactive structure. This is demonstrated by stratigraphical and geomorphological considerations [ Ferranti and Oldow , 1999; Casciello et al , 2006] but also suggested by its subhorizontal attitude, its wave‐shaped trajectory and the crosscut relationships with the SAf high‐angle normal faults. The eastern part, gradually sloping under the Acerno–Monte Raimagra ridge, might acts instead, as a presently active fault on which the high‐angle normal faults, including the SAf and Irf detach.…”

“…In the internal side of the Campania‐Lucania arc, extension generated both low‐angle (LANFs) and high‐angle normal faults. LANFs have been recognized as the cause of diffuse younger‐on‐older subhorizontal tectonic contacts in the Picentini, Maddalena, Lauria and Morano Calabro Mountains [ D ' Argenio et al , 1987; D ' Argenio and Ietto , 1988; Ietto et al , 1992; Ferranti et al , 1996; Ferranti and Oldow , 1999; Casciello et al , 2004, 2006] and have been generally referred to an early extensional stage preceding the origin of the high‐angle normal faults bounding the Quaternary basins.…”

“…Furthermore, the analysis of the literature data (reported below as in the original papers) is complicated by the recent chronostratigraphic revision of the Pliocene–Quaternary boundary which presently corresponds to the Zanclean‐Gelasian passage, whereas until 2010 it was placed at the Gelasian‐Calabrian passage. According to Ferranti and Oldow [1999], in the Salerno area, the activity of the Picentini detachment fault (PiDh, Figure 2) would be bracketed between the upper Miocene and the late Pliocene and would be clearly separated from the high‐angle extension referable to the early Pleistocene–Holocene.…”

Construction of a composite pressure–temperature path: revealing the synorogenic burial and exhumation history of the Sevier hinterland, USA

“…, 1992b; Wallis et al. , 1993; Wells, 1997; Ferranti & Oldow, 1999; Collins, 2002). Despite the theoretical predictions and field examples of alternating shortening and extension, P – T paths confirming such alternations are not widely reported (e.g.…”

“…England & Thompson, 1984). In parallel with the recognition that plate boundary forces, gravitational potential energy, rock rheology and erosion dynamically interact to influence deformation kinematics (Davis et al, 1983;Platt, 1986;Molnar & Lyon-Caen, 1988;England & Houseman, 1989;Royden, 1993;Rey et al, 2001), orogenic histories involving synconvergent extension and alternations in shortening and extension have been documented (Hodges et al, 1992b;Wallis et al, 1993;Wells, 1997;Ferranti & Oldow, 1999;Collins, 2002). Despite the theoretical predictions and field examples of alternating shortening and extension, P-T paths confirming such alternations are not widely reported (e.g.…”