Morphology, distribution, and preservation potential of microbial mats in the hydromagnesite-magnesite playas of the Cariboo Plateau, British Columbia, Canada

Abstract

Benthic microbial mats are common in the alkaline hydromagnesite-magnesite playa lakes of Interior British Columbia. Four main zones are recognized based on mat morphology that can be related to the type and duration of wetting. From the basin margin toward the playa centre they are: (i) vegetated hummocky ground; (ii) polygonal hummocky ground; (iii) low-domal and stratiform mats, and (iv) laterally continuous and pustular mats. Mats in peripheral mudflats are commonly mineralized by hydromagnesite, mostly precipitated by capillary evaporation of shallow groundwaters. Mats forming in the ephemeral lake tend to have lower carbonate content.Although widespread, the mats are poorly preserved in the Holocene sedimentary record. Underlying sediments are commonly weakly bedded, disturbed or massive. Desiccation, dehydration, wettingdrying cycles, and grazing by invertebrates cause fragmentation of mats at the surface, facilitating erosion. Cryogranulation, interstitial mineral precipitation, vesiculation, bioturbation, compaction, and volume changes associated with diagenesis, disrupt and destroy lamination in the upper few centimetres. Most surviving organic matter is lost by early microbial degradation.

The hydromagnesite playas of Atlin, British Columbia, Canada: A biogeochemical model for CO2 sequestration

“…Diatom species of Navicula and Cyclotella are common in this wetland and are sinks for dissolved silicon (Power et al, 2007;Renaut, 1993). Although sepiolite [Mg 4 Si 6 O 15 (OH) 2 ·6H 2 O] is supersaturated in this wetland and in other water bodies in the Atlin area, it has not been detected in any of the sediment samples analyzed by XRD.…”

“…No microbial mat structures are preserved in the grassland sediments. Microbial mats associated with magnesium carbonate sediments have a low preservation potential in regards to forming a microbialite (a fossilized microbial-sedimentary structure; Renaut, 1993). Several factors, including desiccation, cryogranulation, interstitial carbonate precipitation, recrystallization, bioturbation, compaction, and erosion can contribute to poor preservation (Renaut, 1993).…”

“…This model differs significantly from the many industrial methods that have been proposed for CO 2 sequestration. Other environments where this process may be occurring naturally include the playas at Salda Gölü in southwestern Turkey (Braithwaite and Zedef, 1994;Braithwaite and Zedef, 1996;Russell et al, 1999) and the hydromagnesite-magnesite playas of the Cariboo Plateau in British Columbia (Renaut, 1990(Renaut, , 1993.…”

Carbon sequestration via carbonic anhydrase facilitated magnesium carbonate precipitation

“…In this sense, geoengineered systems for sequestering CO 2 may have greater capacity if designed to facilitate Mg-carbonate formation. Typically, hydrated Mg-carbonate minerals, particularly dypingite [Mg 5 (CO 3 ) 4 (OH) 2 ·5H 2 O] and nesquehonite [MgCO 3 ·3H 2 O], are more commonly formed at low pressure and temperature both experimentally and in natural environments (Ferrini et al, 2009;Hänchen et al, 2008;Hopkinson et al, 2008;Kloprogge et al, 2003;McLean et al, 1997;Power et al, 2009Power et al, , 2007Renaut, 1993;Wilson et al, 2010Wilson et al, , 2009. Hydrated Mg-carbonate minerals are metastable relative to magnesite, and require more alkaline pH and greater concentrations of Mg 2+ and DIC to achieve saturation.…”

Carbonate and evaporite sedimentation at Clinton Lake, British Columbia, Canada

“…In a region of <500 km 2, more than 500 saline and hypersaline lakes with N a-C 0 3-(S 0 4)-Cl, N a-C 0 3-Cl, Na-M g-S 04, and M g-N a-S04 brines are found. In the same re gion, there are also many ephemeral lakes with predominantly magnesium carbonate sediments, including abundant magne site, hydromagnesite, and recent dolomite (Cummings, 1940;Grant, 1987;Renaut and Stead, 1991;Renaut, 1993).…”