ABSTRACT: Dolomite, microbiota, and salt lakes of Western Canada.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Dolomite formation and dolomitization in the sedimentary realm are subjects of long-standing interest and study. Probably no other mineral or sedimentary rock has attracted as much speculation regarding its origin and genesis as dolomite. For Quaternarists, modern and Holocene dolomite formation seems to elude a clear understanding, and there is still considerable difference of opinion regarding the occurrence and genesis of "modern" and Quaternary dolomite. As we celebrate the 75th anniversary of the first scientific report on Quaternary lacustrine dolomite, it is fitting to summarize our current understanding of the origin and genesis of this intriguing and economically important mineral in the lakes of western Canada. We also use this opportunity to outline our new phase of investigation and examination directed at deciphering the role of microbiota in initiating and controlling Ca-Mg carbonate mineral formation and diagenesis in these lakes. Western Canada is home to over half of the reported occurrences of modern non-detrital lacustrine dolomite in North America. Nearly all of these are from the saline and hypersaline lakes of the Prairie region of Alberta, Saskatchewan, and Manitoba. Although the precise mechanism(s) by which the dolomite is forming in these lakes remains elusive, there is now overwhelming petrographic and geochemical evidence that most of the fine-grained Ca-Mg carbonate material comprising the lacustrine surficial and Holocene sediment is a true primary precipitate. In Freefight Lake located in southwestern Saskatchewan, and several other deep, saline and meromictic basins, there is evidence that at least some dolomite formation and diagenesis is biologically mediated. It has been shown by various researchers that the production of carbonate particles by some microbes, for example, sulphate-reducing bacteria and cyanobacteria is due to their use of different metabolic pathways of the nitrogen and sulphur cycles. At this point it is not fully understood how these mechanisms induce carbonate precipitation and diagenesis. Our goal in this ongoing research project is to provide insight into the long-standing 'dolomite problem' by examining the role of microbial processes in the formation of carbonates in lakes across a range of environmental conditions. We wish to ascertain if the precipitation is due in part to changes in the water chemistry caused by these metabolic processes (i.e., an increase in alkalinity) and/or by a change in the microbial cells that encourages nucleation and growth of the mineral.

Bibliography of Canadian Geomorphology