Skip to Main Content
Book Chapter

Influence of microbial framework on Cryogenian microbial facies, Rasthof Formation, Namibia

By
E. Le Ber
E. Le Ber
Search for other works by this author on:
D. P. Le Heron
D. P. Le Heron
Earth Science Department, Royal Holloway University of London, Egham Hill, Egham TW20 0EX, Surrey, UK
Search for other works by this author on:
N. H. Oxtoby
N. H. Oxtoby
Earth Science Department, Royal Holloway University of London, Egham Hill, Egham TW20 0EX, Surrey, UK
Search for other works by this author on:
Published:
January 01, 2015

Abstract

The Rasthof Formation is a mid-Cryogenian cap carbonate succession deposited in Namibia following the Sturtian glaciation. It includes a microbial member, typically >100 m thick. This member exhibits contorted intervals, and is divisible into two informally defined units. The lower unit (microbial member 1: MM1) comprises thickly laminated microbialites (1–6 mm); the upper unit (MM2) is characterized by thinly laminated microbialites (sub-millimetre layering). Contortion of the microbialite deposits – a recurrent feature of this succession – is interpreted to result from soft-sediment deformation. Deformed intervals and styles range from metre- to decimetre-scale chaotic folds in MM1 to a few centimetre-scale, localized roll-up structures in MM2. Study of the microfacies of MM1 and MM2 reveals two essentially different architectures. In MM1 the microfacies is dominated by an alternation of thin micritic laminae with thicker cemented intervals; this probably gave less rigidity to the sediments than in MM2 where the laminated fabric is also present but connected vertically as well, forming a continuous framework. We suggest that the continuity of this framework limited the frequency and scale of soft-sediment deformation. In the Rasthof Formation, the microarchitecture is thus suggested to translate into different degrees of rigidity of the macrofacies.

You do not currently have access to this article.

Figures & Tables

Contents

Geological Society, London, Special Publications

Microbial Carbonates in Space and Time: Implications for Global Exploration and Production

D. W. J. Bosence
D. W. J. Bosence
Royal Holloway, University of London, UK
Search for other works by this author on:
K. A. Gibbons
K. A. Gibbons
Nexen Petroleum UK Ltd, UK
Search for other works by this author on:
D. P. Le Heron
D. P. Le Heron
Royal Holloway, University of London, UK
Search for other works by this author on:
W. A. Morgan
W. A. Morgan
Morgan Geoscience Consulting, LLC, USA
Search for other works by this author on:
T. Pritchard
T. Pritchard
BG Group, UK
Search for other works by this author on:
B. A. Vining
B. A. Vining
Royal Holloway, University of London, UK
Search for other works by this author on:
Geological Society of London
Volume
418
ISBN electronic:
9781862397163
Publication date:
January 01, 2015

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal