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Moema laminites: a newly recognized Neoproterozoic (?) glaciogenic unit, São Francisco Basin, Brazil

By
Antonio C. Rocha-Campos
Antonio C. Rocha-Campos
Instituto de Geociências, Universidade São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, SP, Brazil
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Benjamin B. De Brito Neves
Benjamin B. De Brito Neves
Instituto de Geociências, Universidade São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, SP, Brazil
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Marly Babinski
Marly Babinski
Instituto de Geociências, Universidade São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, SP, Brazil
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Paulo R. Dos Santos
Paulo R. Dos Santos
Instituto de Geociências, Universidade São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, SP, Brazil
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Sônia M. B. De Oliveira
Sônia M. B. De Oliveira
Instituto de Geociências, Universidade São Paulo, Rua do Lago, 562, Cidade Universitária, São Paulo, SP, Brazil
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A. Romano
A. Romano
Instituto de Geociências, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
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Published:
January 01, 2011

Abstract

A recently identified diamictite and silt-clay laminite, which discordantly overlie the Archaean basement and underlie the Neoproterozoic Bambui Group, have been informally named as the Moema Laminites. They are preserved at the southwestern margin of the São Francisco Basin in southeastern Brazil, and are widely distributed in the central-western Minas Gerais state. They crop out discontinuously over at least 140 km along a north–south direction. The nomenclature of and stratigraphic relationships between the Moema Laminites and other isolated Neoproterozic occurrences of similar rocks are in a state of flux. Two exceptionally good exposures of the Moema Laminites show good evidence for deposition under glacial conditions. At the Formiga locality, a single glacial advance is registered by a deformation tillite, while overlying laminite records deposition in a post-glacial, probably marine basin following deglaciation. At the SAFFRAN quarry, striations on a bedding plane may have been caused by floating sea-ice that just touched the bottom of the basin. Much additional work is needed to establish relationships between the Moema Laminites and other similar occurrences. If these and Moema Laminites are shown to be Cryogenian glacial deposits, the area covered by the Cryogenian glaciations in the São Francisco basin is much larger than formerly believed.

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Contents

Geological Society, London, Memoirs

The Geological Record of Neoproterozoic Glaciations

Emmanuelle Arnaud
Emmanuelle Arnaud
University of Guelph, Canada
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Galen P. Halverson
Galen P. Halverson
McGill University, Canada
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Graham Shields-Zhou
Graham Shields-Zhou
University College London, UK
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Geological Society of London
Volume
36
ISBN electronic:
9781862394117
Publication date:
January 01, 2011

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