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The Hercynian orogeny in the South Armorican Massif (Saint‐Georges‐sur‐Loire Unit, Ligerian Domain, France): rifting and welding of continental stripes
Author(s) -
Cartier C.,
Faure M.,
Lardeux H.
Publication year - 2001
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1046/j.1365-3121.2001.00334.x
Subject(s) - geology , massif , devonian , accretionary wedge , orogeny , rift , subduction , fibrous joint , paleontology , paleozoic , seismology , geomorphology , tectonics , medicine , anatomy
A new approach to explain the Western Hercynian Belt is given by a lithological and structural study of the St‐Georges‐sur‐Loire Unit (southern part of the French Armorican Massif). This unit is interpreted as a Devonian olistostrome sheared to the North. It is formed in an accretionary prism linked with a south‐dipping subduction zone, called the Layon subduction zone. It results from a chaotic sedimentation including exotic blocks of various lithologies and ages in a Middle Devonian pebbly mudstone matrix. An inovative geodynamic model involving microblock rifting and collision is discussed to explain the presence of the St‐Georges‐sur‐Loire Unit in the Armorican Massif. This model involves two Palaeozoic subductions and emphasizes the role of the Nort‐sur‐Erdre fault, considered as a major polyphase suture zone separating South and Central Armorica.