Open Access
Table 1
Summary table of the main sedimentological, structural and petrographical characteristics recognized in the field for each type of breccias.
Synthèse des caractéristiques sédimentologiques, structurales et pétrologiques des différents types de brèches.
| Breccia type | Type-1 | Type-2 | Type-2bis | Type-3 | Type-4 | Type-5 | Type-5bis |
|---|---|---|---|---|---|---|---|
| Related figures | 5a–e, 6, 7c–e, 8d–h | 5f-g, 7g, 8b-c, 11b–d | 7f | 9 | 11e | 11f-i | 11j-k |
| Thickness | 50 to 100 m | 10 to 20 m | < 5 m | 250 m | 5 m | 200 to 300 m | < 10 m |
| Structure | In contact with the basement, via albitized fault zones | Intraformationnal in the deformed basal Lias | Same as type-1 | Marks an extensional contact between basement and cover | Marks the contact between basement and cover | Intraformationnal in the Dogger- lower Cretaceous interval | Same as type-3, but following stratigraphic interfaces |
| Clasts origin | Pre-Aptian Mesozoic cover, Saint Arnac granite and its country-rocks | Liasis ductile deformed limestones | Same as type-1 | Pre-Aptian Mesozoic cover, schists, granulites and migmatites | Lias, Trias and Paleozoic Schists | Triassic to Albian Mesozoic cover | Pre-Aptian Mesozoic cover |
| Texture | Matrix supported, local coarsening upward clasts distribution | Clasts supported | Same as type-1 | Matrix supported | Matrix supported | Matrix supported | Matrix supported |
| Clasts morphology | Sub-angular to rounded, sub-spherical | Angular to very angular, flat | Same as type-1 | Sub-angular to rounded, sub-spherical | Sub-angular to rounded, sub-spherical | Angular to sub-rounded, sub-spherical | Sub-angular to angular, flat |
| Matrix or cement nature | Particulate carbonate matrix, with clayey to fine sandy grain-size | Cement made of calcitic veins + coarse carbonate particle | Cement made of calcitic veins + coarse carbonate particle | Calcarenite and calcitic veins | Calcarenite and calcitic veins | Particulate carbonate matrix, with gypsum and calcictic veins | Carbonate mud |
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