Age and depositional environment of the Sainte-Anne formation (Armorican Massif, France): The oldest (Emsian) evidence for mountain erosion in the variscan belt - Archive ouverte HAL Access content directly
Journal Articles Bulletin de la Société Géologique de France Year : 2009

Age and depositional environment of the Sainte-Anne formation (Armorican Massif, France): The oldest (Emsian) evidence for mountain erosion in the variscan belt

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Christine Strullu-Derrien
  • Function : Author
  • PersonId : 881206
Michel Ballevre
  • Function : Author
  • PersonId : 841742
Marie-Pierre Dabard
  • Function : Author
  • PersonId : 840697
Hubert Lardeux
  • Function : Author
Cécile Robin
  • Function : Author
  • PersonId : 836508

Abstract

The palaeogeography of the internal zones of the Variscan belt during the early stages of the convergence remains unclear. Sedimentary sequences that recorded the denudation of an early relief have generally been removed by erosion. In the Chalonnes area (southeast of the Armorican Massif), the reefal carbonates of the Chalonnes Formation (Fm) are overlain by the immature, poorly-sorted sandstones of the Sainte-Anne Fm. This formation is characterised by the occurrence of gravity flow deposits and contains immature and poorly sorted sandstones with a large amount of plant debris and lithic fragments, suggesting a depositional environment in a delta front dominated by floods. A revision of the palaeoflora content allows to assign an Emsian age to the Sainte-Anne Fm. Lithic fragments are mainly of sedimentary and volcanic origin, suggesting moderate erosion level of the source area. Palaeocurrent data indicate a southern origin for the sediments. These features collectively demonstrate that the Sainte-Anne Fm is the record of the erosion of a continental area located farther south, and experiencing incipient tectonic uplift during the Emsian. The Sainte-Anne Fm could represent therefore the earliest record in France of the very first stages of the Variscan orogeny.
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Dates and versions

insu-00562472 , version 1 (03-02-2011)

Identifiers

  • HAL Id : insu-00562472 , version 1

Cite

Céline Ducassou, Christine Strullu-Derrien, Michel Ballevre, Marie-Pierre Dabard, Philippe Gerrienne, et al.. Age and depositional environment of the Sainte-Anne formation (Armorican Massif, France): The oldest (Emsian) evidence for mountain erosion in the variscan belt. Bulletin de la Société Géologique de France, 2009, 180 (6), pp.529-544. ⟨insu-00562472⟩
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