Evidence for preorogenic Early Devonian rifting

Authors: Céline Ducassou Michel Ballèvre Hubert Lardeux Cécile Robin

Publish Date: 2010/12/22

Volume: 100, Issue: 7, Pages: 1451-1475

PDF Link

Abstract

The Palaeozoic sediments from the Mauges Unit Armorican Massif France are the bestpreserved preorogenic sequences belonging to the Upper Allochthon Two coherent sequences are identified The southern unit Châteaupanne Unit represents the cover of the Proterozoic basement and consists of Ordovician sediments unconformably overlain by Emsian carbonates followed by Emsian to earliest Eifelian immature sandstones The northern unit Tombeau Leclerc Unit consists of an Hirnantian to Emsian condensed sequence in reverse position that has been thrust over the southern unit The Devonian unconformity is interpreted as evidence for an Early Devonian extension recorded by normal faults affecting both the Early Devonian limestones and the underlying Ordovician series This crustal extension recorded here for the first time is possibly related to the opening of a backarc basin SaintGeorgessurLoire associated with the subduction of an ocean located further south GaliciaBrittanyMassif Central OceanThis paper is part of a PhD project CD devoted to the initiation of the relief in Variscan belt and is financed through a grant to CD Discussions with many people have contributed to clarify some of the issues especially JR Martínez Catalán and J Abati who visited the investigated area We would like to thank both Martin Keller and Sven Egenhoff for their critical reviews Karel Schulmann Nick Timms and an anonymous reviewer helped to improve a previous version of this manuscript The authorizations for working in the Châteaupanne quarry were provided by its director E Souchet and his quarry chief J Binet Mr and Mrs Porcher and M and E Mercier kindly allowed us to access the SainteAnne abandoned quarry and to the Orchère locality respectively The English language has been revised by Dr Sara Mullin

Keywords: