干旱区生态环境知识资源中心

The Ibero-Armorican Arc is the main Variscan macrostructure in SW Europe. Its branches preserve the Cambrian record of a continuous margin of West Gondwana, from its southwestern edge (West Asturian-Leonese and Cantabrian zones and their lateral continuity into the Iberian Chains) to its northeastern extension (basement of the Cenozoic Aquitaine basin, Montagne Noire, southern Cevennes, and Sardinia). These Variscan relics allow the reconstruction of a Cambrian Epoch 2 carbonate belt that developed intermittently along West Gondwana. Facies associations show that the main centres of carbonate productivity were nucleated in ooidal and sand shoals, together with microbial and microbial-archaeocyathan reefs, developed in high energy regimes under subtropical arid conditions. Outside the inner carbonate belt, carbonate production was episodic and related to deposition of kerogenous black shales and phosphogenesis in the Central Iberian Zone and northern parts of Montagne Noire and Cevennes. Development of carbonate platforms along the margin was diachronous and discontinuous, due to poleward drifting and tectonically induced drowning and flooding. Biogeographic connection with similar subtropical carbonate platforms from East Gondwana (mainly South China) favoured the migration of equatorial and subtropical trilobite genera, such as Dolerolenus, Eoredlichia, Metaredlichia, Protolenus, Redlichia, and Sardaspis.