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The Morello Tectonic Unit in the Tuscan Apennines (Italy) represents the result of tectonosedimentary deformation, occurring in the frontal part of the non-metamorphosed Ligurian Accretionary Wedge, which consists of ophiolitic slices imbricated with a sedimentary succession containing ophiolite-bearing sedimentary mélanges. Geological mapping and structural and stratigraphic observations allow us to document that (1) the ophiolite-bearing sedimentary mélanges formed by gravitational reworking of material sourced from intrabasinal structural highs facing the oceanic basin environment from the Jurassic to early Eocene, before the middle Eocene accretion stage, and (2) the ophiolitic tectonic slices represent the scraping off at shallow structural levels of part of this sequence of crustal oceanic highs. The final internal architecture of the shallow frontal portion of the Ligurian Accretionary Wedge does not differ from those observed in metamorphosed orogenic belts and exhumed accretionary complexes throughout the world (e.g. blueschist and eclogite units of the Western Alps). This suggests that to the classical model of subduction and metamorphism followed by accretion and mélange formation (i.e. underplating), a model in which frontal accretion and ophiolite mélange formation at a shallow level are followed by underthrusting and subduction can be added, providing additional constraints for a better reconstruction of the evolution of orogenic belts and accretionary complexes. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists [ABSTRACT FROM AUTHOR]

Multiple magnetic fabrics, referred to as F1–F5, were revealed through the anisotropy of magnetic susceptibility in an Ocean Plate Stratigraphy (OPS) mélange of the Neoproterozoic–Cambrian Blovice accretionary complex, Bohemian Massif. The fabrics post-date the formation of the mélange and the rotation of basalt blocks within the matrix and are interpreted in terms of a complex structural history of the mélange. Excluding local fabrics, the F1 fabric formed earlier along the mélange belt, recording shortening of the accretionary wedge front, whereas the higher grade F4 fabric pervasively overprinted both blocks and matrix in the SW part of the belt, recording shearing and vertical shortening at deeper structural levels closer to a megathrust surface. The preservation of angular relationships between the F1 and F4 fabrics across different parts of the mélange suggests that the blocks were only strained and not rotated during deformation, exemplifying the notion that the OPS mélanges may be a product of deformation at very shallow levels. The F1–F5 fabrics may be viewed as snapshots in a protracted evolution of OPS, where the earlier fabrics in basalt blocks may record the travel path of an oceanic plate from mid-ocean ridge towards the trench, before being overprinted in the accretionary wedge. Thematic collection: This article is part of the Ophiolites, melanges and blueschists collection available at: https://www.lyellcollection.org/topic/collections/ophiolites-melanges-and-blueschists Supplementary material: Thin-section photomicrographs, anisotropy of magnetic susceptibility data and summary diagrams for magnetic fabric types are available at https://doi.org/10.6084/m9.figshare.c.7008173 [ABSTRACT FROM AUTHOR]