Distinct magnetic fabric in weakly deformed sediments from extensional basins and fold-and-thrust structures in the Northern Apennine orogenic belt (Italy)

Abstract

International audienc

Distinguishing the Mélange-Forming Processes in Subduction-Accretion Complexes: Constraints from the Anisotropy of Magnetic Susceptibility (AMS)

“…We used the contour diagram for the principal susceptibility axes distribution for isolating the AMS contribution of subfabrics, if any (e.g., primary sedimentary fabric from tectonic fabric) [101,[103][104][105][107][108][109][110]. As a matter of fact, subfabrics, due to distinct processes or events, may be expressed in different mineral and/or grain-size fractions and are superposed in the conventionally observed AMS [103].…”

Application of anisotropy of magnetic susceptibility (AMS) fabrics to determine the kinematics of active tectonics: examples from the Betic Cordillera, Spain, and the Northern Apennines, Italy

“…The Northern Apennines are an accretionary fold and thrust belt (Bally et al, 1986) where crustal deformation, rock uplift, and topographic growth result from the ongoing subduction of Adria beneath Europe (Picotti and Pazzaglia, 2008;Carminati and Doglioni, 2012). The Apennine orogenic wedge initiated ∼ 30 Ma along the southern flank of the Alps (Le Pichon et al, 1971) and has grown at variable rates through the Neogene dependent on the transfer of mass imbricated from the subducting plate (Picotti and Pazzaglia, 2008).…”

“…Rapid rollback of Adria with respect to Europe results in retreat and stretching of the upper plate, forming a wide zone of back arc crustal extension. The Apennine wedge started to become emergent ∼ 4 Ma (Picotti and Pazzaglia, 2008), uplifting and exposing paired compressional and extensional deformation fronts near the trench and in the forearc, respectively, with the structural transition near the topographic culmination of the range (D'Agostino et al, 2001;Carminati and Doglioni, 2012). Balanced cross sections for the Apennines (Bally et al, 1986;Hill and Hayward, 1988) indicate ∼ 130 to 150 km of subduction over the 30 Myr history of the wedge, which indicates relatively slow long-term rates at ∼ 4 to 5 km Myr −1 (4-5 mm yr −1 ), similar to the GPS geodetic rates (Devoti et al, 2008;Caporali et al, 2011;Bennett et al, 2012).…”

“…A number of circum-Mediterranean orogens are associated with rapid slab rollback, resulting in paired compressional and extensional domains in the orogenic wedge of the retreating upper plate (Elter, 1975;Carminati and Doglioni, 2012). Examples include the Calabria Arc-Tyrrhenian Sea (Beccaluva et al, 1985;Milia et al, 2009), the Hellenic Arc-Aegean Sea (Le Pichon and Angelier, 1979;Papazachos et al, 2000), and the Gibraltar Arc-Alboran Sea (Lonergan and White, 1997;Platt et al, 2006;Fernández-Ibáñez and Soto, 2008).…”

Strain patterns in glacitectonically thrusted sediments and conditions during thrusting

“…Additional insights into the fabric patterns at Rubjerg Knude and Møns Klint come from studies of AMS fabric development in deformed rocks (see Borrradaile and Henry, 1997; Parés, 2015, for reviews) and sediments (e.g., Collombat et al, 1995;Housen and Kanamatsu 2003;Caricchi et al, 2016) in crustal tectonic environments. A leading model developed from such field studies (notably by Averbuch et al, 1992;Borradaile and Henry, 1997;Bakhtari et al, 1998;Saint-Bezar et al, 2002) and more recently tested in analogue sandbox experiments (Almqvist and Koyi, 2018) allows interpretation of fabrics resulting from layer-parallel shortening (LPS) in fold and thrust belts and accretionary prisms.…”