Large submarine slides on a steep continental margin (Camamu Basin, NE Brazil)

P.R. Cobbold (1) , Gil Gilchrist , Dario Chiossi , Fabiana Fonseca-Chaves , Fernando Gomez de Sousa , Ragnhild Lilletveit

1 GR - Géosciences Rennes

We describe a set of unusually large submarine slides from the Camamu Basin, on the continental margin of NE Brazil. The margin is about 50 km wide and the sea floor has a slope of up to 4°. The sedimentary cover is up to 7 km thick. Neocomian strata, up to 3 km thick, accumulated during continental rifting. Shale in the lower part is equivalent to the main source rock of the neighbouring Reconcavo Basin. Aptian strata consist mainly of coarse clastic sediment and evaporite. Late Cretaceous strata are thin or absent and the Tertiary succession is about 1 km thick, above a prominent Eocene unconformity. The Neocomian and Aptian sequences contain abundant thin-skinned structures, extensional near the continental shelf, and compressional toward the toe of slope. The structures have detached on Aptian evaporite, and also at the base of Neocomian shale. The largest slide is about 5 km thick and 100 km wide. It displays mirror symmetry about a vertical plane perpendicular to the margin. The main phase of sliding occurred between the late Aptian and the middle Eocene. The trigger may have been a regional phase of uplift and exhumation.

Domaines: Stratigraphie

P.R. Cobbold, Gil Gilchrist, Dario Chiossi, Fabiana Fonseca-Chaves, Fernando Gomez de Sousa, et al.. Large submarine slides on a steep continental margin (Camamu Basin, NE Brazil). Gravitational Collapse at Continental Margins, Geological Society, Oct 2008, Londres, United Kingdom. ⟨insu-00376315⟩