Journal ArticleDOI
Dolomite formation within microbial mats in the coastal sabkha of Abu Dhabi (United Arab Emirates)
Tomaso R. R. Bontognali,Crisogono Vasconcelos,Rolf Warthmann,Stefano M. Bernasconi,Christophe Dupraz,Christian J. Strohmenger,Judith A. McKenzie +6 more
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In this article, a geochemical and petrographic investigation of three sites located on the coastal sabkha of Abu Dhabi, along a transect from the intertidal to the supratidal zone, revealed a close association between microbial mats and dolomite.Abstract:
Microbial mediation is the only demonstrated mechanism to precipitate dolomite under Earth surface conditions. A link between microbial activity and dolomite formation in the sabkha of Abu Dhabi has, until now, not been evaluated, even though this environment is cited frequently as the type analogue for many ancient evaporitic sequences. Such an evaluation is the purpose of this study, which is based on a geochemical and petrographic investigation of three sites located on the coastal sabkha of Abu Dhabi, along a transect from the intertidal to the supratidal zone. This investigation revealed a close association between microbial mats and dolomite, suggesting that microbes are involved in the mineralization process. Observations using scanning electron microscopy equipped with a cryotransfer system indicate that authigenic dolomite precipitates within the exopolymeric substances constituting the microbial mats. In current models, microbial dolomite precipitation is linked to an active microbial activity that sustains high pH and alkalinity and decreased sulphate concentrations in pore waters. Such models can be applied to the sabkha environment to explain dolomite formation within microbial mats present at the surface of the intertidal zone. By contrast, these models cannot be applied to the supratidal zone, where abundant dolomite is present within buried mats that no longer show signs of intensive microbial activity. As no abiotic mechanism is known to form dolomite at Earth surface conditions, two different hypotheses can reconcile this result. In a first scenario, all of the dolomite present in the supratidal zone formed in the past, when the mats were active at the surface. In a second scenario, dolomite formation continues within the buried and inactive mats. In order to explain dolomite formation in the absence of active microbial metabolisms, a revised microbial model is proposed in which the mineral-template properties of exopolymeric substances play a crucial role.read more
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Bacteria and archaea on Earth and their abundance in biofilms
TL;DR: It is proposed that biofilms drive all biogeochemical processes and represent the main way of active bacterial and archaeal life and are the most prominent and influential type of microbial life.
Journal ArticleDOI
The Meaning of Stromatolites
TL;DR: In this paper, a model that integrates stromatolite scales, macroscopic organization, and shapes could also help test the biogenicity of the oldest stromata.
Journal ArticleDOI
Microbially catalyzed dolomite formation: From near-surface to burial
Daniel A. Petrash,Or M. Bialik,Tomaso R. R. Bontognali,Crisogono Vasconcelos,Jennifer A. Roberts,Judith A. McKenzie,Kurt O. Konhauser +6 more
TL;DR: A review of the direct and indirect mechanisms by which microbes facilitate the nucleation and shallow burial diagenetic stabilization of dolomite in marine sediments is presented in this paper.
Journal ArticleDOI
An abiotic model for the development of textures in some South Atlantic early Cretaceous lacustrine carbonates
V. Paul Wright,Andrew Barnett +1 more
TL;DR: In this paper, the cyclic distribution of various types of carbonates and Mg-clays in early Cretaceous rift-sag phase lacustrine carbonates from the subsurface of the South Atlantic provides an insight into how evolving lake chemistries in highly alkaline settings control facies development.
References
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Journal ArticleDOI
The role of microbes in accretion, lamination and early lithification of modern marine stromatolites
R. P. Reid,Pieter T. Visscher,Alan W. Decho,John F. Stolz,Brad M. Bebout,Christophe Dupraz,Ian G. Macintyre,Hans W. Paerl,James L. Pinckney,Leslie Prufert-Bebout,Timothy F. Steppe,David J. DesMarais +11 more
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TL;DR: The role of mineralogy in the Petrology of Sedimentary carbonates is discussed in this paper. But this work is limited to the case of Calcite-Aragonite.