SeismicScale Rafted and Remnant Blocks over Salt

Authors: Davide Gamboa Tiago Alves Joe Cartwright

Publish Date: 2012

Volume: , Issue: , Pages: 629-638

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Abstract

The EoceneOligocene stratigraphic succession of the Espírito Santo Basin SE Brazil comprises several MassTransport Deposits MTDs some of which contain individual blocks of strata The blocks are classified as rafted blocks if transported over a glide plane or remnant blocks if in situ showing vertical stratigraphic continuity with underlying strata A detailed 3D seismic analysis of a masstransport deposit MTDA1 deposited at the base of an Eocene volcaniclastic complex Abrolhos complex reveals the presence of various blocks within the masses of failed strata Blocks occur in the thickest areas of the MTD along an alignment of salt diapirs and buried salt ridges Block fragmentation is suggested to be associated to diapirrelated faults especially when these are closely aligned with insitu blocks The remnant blocks show low deformation with subhorizontal internal reflections whereas rafted ones range from low to highly deformed blocks Variations in the blocks’ geometries suggest a lateral remobilisation in the order of 1000 m for a maximum of 4000 m for MTDA1 The low remobilisation led to an unusual location of the MTD over the salt structures contrasting with the typical remobilisation towards peripheral basins The relation between MTD and saltrelated structures can provide indicators to constrain the timing of halokinesisThe authors are grateful to CGGVeritas for the permission conceded to publish this research paper Jose FreyMartínez and Mads Huuse are thanked for their comments on early versions of the manuscript D Gamboa thanks the Fundação para a Ciência e a Tecnologia FCT for the SFRH/BD/38819/2007 PhD grant

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