A RECORD OF FRONTAL TECTONIC EROSION IN A FOSSIL ACCRETIONARY WEDGE: THE EXAMPLE OF THE BOCCO SHALE MÉlange, INTERNAL LIGURIDE OPHIOLITIC SEQUENCE (NORTHERN APENNINE, ITALY)

PANDOLFI, Luca, Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria, 53, Pisa, I-56126, Italy, MARRONI, Michele, Dipartimento di Scienze della Terra, Università di Pisa, via Santa Maria 53, Pisa, 56126, Italy and MENEGHINI, Francesca, Earth Sciences Department, Stellenbosch University, Private Bag X1, Matieland, Stellenbosch, 7602, South Africa, pandolfi@dst.unipi.it

In the Northern Apennines (Italy), the Internal Liguride units are characterized by an ophiolite sequence that represents the stratigraphic base of a Late Jurassic-Early Paleocene sedimentary cover. The Bocco Shale represents the youngest deposit recognized in the sedimentary cover of the ophiolite sequence. The deposits belonging to the Bocco Shale can be subdivided into two different groups of deep sea sediments. The first group is represented by slide, debris flow and high density turbidity current-derived deposits, whereas the second group consists thin bedded turbidites. Facies analysis and provenance studies indicate, for the former group, small and scarcely evoluted flows that rework an oceanic lithosphere and its sedimentary cover.

According to their overall features, the Bocco Shale can be interpreted as an ancient example of a deposit related to the frontal tectonic erosion of an accretionary wedge. The frontal tectonic erosion was probably connected with subduction of oceanic crust characterized by extensive topographic reliefs. The topographic reliefs were probably originated by reactivation of former Jurassic faults during the bending of the oceanic lithosphere as it was approaching the trench. The frontal tectonic erosion resulted in a large removal of material from the accretionary wedge front reworked as debris flows and slide deposits, i.e. the Bocco Shale, directly sedimentated on the faulted lower plate.

The occurrence of debris flow- and slide-derived deposits at the top of the ophiolite sedimentary cover is a common feature of the oceanic units from Apennine, Corsica and Western Alps. We propose for all of these deposits an origin related to frontal tectonic erosion, that represented a common process during the convergence-related evolution of the Ligure-Piemontese oceanic basin in the Late Cretaceous-Early Tertiary time span.

Session No. 19

Mélanges and mélange–forming processes. Part 1

Tuesday, 5 October 2010: 09:30-12:30

Salon A (METU Convention and Cultural Centre)

© Copyright 2010 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.

Back to: Mélanges and mélange–forming processes. Part 1

<< Previous Abstract | Next Abstract >>

Tectonic Crossroads: Evolving Orogens of Eurasia-Africa-Arabia

A RECORD OF FRONTAL TECTONIC EROSION IN A FOSSIL ACCRETIONARY WEDGE: THE EXAMPLE OF THE BOCCO SHALE MÉlange, INTERNAL LIGURIDE OPHIOLITIC SEQUENCE (NORTHERN APENNINE, ITALY)