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6.2. Grande Brèche Viséenne - GDB

Authors: Pirlet, 1972

Description: Breccia with boulders of limestone in a matrix which is often red. The “Grande-Brèche” resulted from dissolution of evaporitic levels in the Maizeret Mbr of the Grands Malades Fm (Mamet et al., 1986), but was probably also related to Variscan tectonics (Pirlet, 1972). Thus, it cannot be considered here as a lithostratigraphic unit.

Area: Western NSA, CSA, DSA.

Thickness: About 40 m, but sometimes more because in places the Visean formations overlying the Maizeret Mbr are also brecciated.

Age: Post-Livian to post-Visean.