A tectonically-induced Eocene sedimentary mélange in the West Ligurian Alps, Italy

Abstract

succession. Submarine ridges were generated and favoured rock fall phenomena that involved both small, mm-to dm-sized, clasts and huge slabs detached from the main rock masses. These morphostructural highs were flanked by oversteepened slopes affected by failures that gave rise to debris flows, involving hemipelagic muds and turbidite sands and lithified fragments of older formations, which resulted in strongly polygenic paraconglomerates. The studied mélange is thus fully due to sedimentary processes that were, however, completely controlled by early Alpine tectonics.

The Šariš Transitional Zone, revealing interactions between Pieniny Klippen Belt, Outer Carpathians and European platform

“…Concurrent tectonic and gravitational motions leading to the formation of polygenetic olistostromes are common in a large part of the Western Alps at the top of the Alpine foreland basin succession (Perotti et al 2012) and in the Northern Apennines (Pini 1999;Codegone et al 2012;Ogata et al 2012). Also the Miocene of the Outer Carpathians is full of chaotic sediments, the diachronous character of which has been underlined by Jankowski and Jarmołowicz-Szulc (2009).…”

Geology of the Entracque–Colle di Tenda area (Maritime Alps, NW Italy)

“…This document is, thus, the first published detailed map as part of a scientific programme focusing on the revision of the stratigraphic and tectonic setting of a large area encompassing, from NW to SE, the Italian side of the Maritime Alps and the westernmost part of the Ligurian Alps, the main results of which have been recently published (Barale et al, 2013;Bertok, Martire, Perotti, d'Atri, & Piana, 2011d'Atri, Piana, Barale, Bertok, & Martire, submitted;Martire, Bertok, d'Atri, Perotti, & Piana, 2014;Perotti et al, 2012;Piana et al, 2009Piana et al, , 2014.…”

The thrust zone of the Ligurian Penninic basal contact (Monte Fronté, Ligurian Alps, Italy)

“…These topographic maps have been used to produce a new simplified version with 50 m contour interval, in order to allow clear data presentation. The description of lithostratigraphic units (Figure 2) follows previous fieldwork performed in the study area (Giammarino et al, 2010;Lanteaume, 1962;Lanteaume et al, 1990;Perotti et al, 2012). The main structural data -that is, the trace of thrusts and faults, the attitude of foliations and fold axes -are shown on the map.…”

“…However, between the foreland basin succession and the PBC thrust, a thick succession comprising chaotic deposits occurs. This succession has been named with different terms on the basis of the interpretation of its (sedimentary and/or tectonic) nature: 'Zone des Lambeaux de charriage' of Lanteaume (1962), 'Complexe olistostromatique' of Lanteaume (1968) and Lanteaume et al (1990), 'Zona dei Lembi Interposti' of Vanossi (1991), Tectonic Unit of Baiardo-Triora of Giammarino et al (2010) and 'Triora Olistostrome Member' (TOM) of Perotti et al (2012). Our fieldwork shows that this succession should be divided in two different structural units (Main Map; Figure 2): in fact, chaotic rocks stratigraphically overlay both the foreland basin succession and a substratum-derived tectonic sheet (the Rocca Barbone Unit), which is included between two thrust planes (the Monte Fronté Thrust and the Rocca Barbone Thrust) constituting the PBC.…”

“…In the Ligurian Alps (Figure 1), chaotic deposits occur in the footwall of the Penninic Basal Contact (PBC) (Ceriani, Fugenschuh, & Schmid, 2001) separating the allochtonous nappes (the Helminthoid Flysch nappes) from the foreland basin succession developed onto the external European crust (Kerckhove, 1969). These deposits have been controversially interpreted as originating from sedimentary (Lanteaume, 1968;Lanteaume, Radulescu, Gavos, & Feraud, 1990;Perotti et al, 2012) or tectonic processes (Giammarino, Fanucci, Orezzi, Rosti, & Morelli, 2010;Lanteaume, 1962;Vanossi, 1991) mainly on the basis of the detection (or not) of major tectonic or stratigraphic discontinuities within or at the base of the chaotic bodies.…”