Lacustrine-evaporitic microbial dolomite from a Plio-Pleistocene succession recovered by the SG-1 borehole in the Qaidam Basin, NE Tibetan Plateau

Lacustrine dolomite in deep time: What really matters in early dolomite formation and accumulation?

“…10A). This lacustrine-evaporitic microbial dolomite is supported by several lines of evidence: i) Brackish lakes like those in the Zhanhua and Dongying sags of the Bohai Bay Basin contain much less dolomite than calcite in their lake-center shales (Zhang et al, 2016;Teng, 2018;Teng et al, 2022;Zhao et al, 2023), whereas (hyper)saline lakes like those in the Qianjiang Sag of the Jianghan Basin and in the Mangya Sag of the Qaidam Basin contain more dolomite than calcite (Fig. 3B) (Yuan et al, 2015;Li et al, 2018;Guo et al, 2019;Kong et al, 2020).…”

“…Although microbial activity is very important in dolomite formation at low temperature in modern depositional settings, it is an intrinsic condition that determines where and how dolomite formation occurs, which is further controlled by environmental conditions such as lake water hydrochemistry and temperatures. Without external favorable conditions, such as the availability of Mg 2+ and Ca 2+ ions and organic matter, the probability of dolomite formation induced by microbial activity will be largely reduced (Zhao et al, 2023). The suggested climatic evaporation, hydrothermal activity and alteration of tuff materials in different models for dolomite accumulation in lacustrine depositional systems contributed to a common result that the Mg 2+ / Ca 2+ ratios of bulk lake waters or porewaters have been largely increased.…”

Searching for microbial contribution to micritization of shallow marine sediments

“…The same mechanism is valid for negative charges on the bacterial cell wall (Gonz alez- Muñoz et al, 1996;Görgen et al, 2021;Marvasi et al, 2017;Perito et al, 2014;S anchez-Rom an et al, 2007S anchez-Rom an et al, , 2008 For instance, ureolytic (e.g., Sporosarcina pasteurii) and sulfate-reducing (e.g., Desulfovibrio spp.) bacteria are examples of heterotrophs affecting the carbonate turnover, as their specific metabolisms can increase the local pH, promoting carbonate precipitation (Almahamedh, 2013;Bachmeier et al, 2002;Görgen et al, 2021;Krause et al, 2012;Pineda et al, 2021;Robles-Fernandez et al, 2022;Zhao et al, 2023). Other pathways, such as fatty acid and nitrogen-related metabolisms, can also play a role in biologically-induced biomineralization (Görgen et al, 2021;Van Paassen et al, 2010).…”

“…Described as engines of a massive biological pump responsible for atmospheric oxygenation and carbon fixation, green algae and cyanobacteria are central elements of sediment early diagenesis (Areias et al, 2022; Popall et al, 2020; Sánchez‐Baracaldo et al, 2022; Zhao et al, 2023). In micritization, they have been described as the key players in grain microboring (Alexandersson, 1972; Bathurst, 1966; Dupraz et al, 2009; Kobluk & Risk, 1977b), and in modern shallow marine settings, they are the main endoliths infesting and actively affecting carbonate precursors (Garcia‐Pichel, 2006; Garcia‐Pichel et al, 2010; Reid et al, 2000).…”

“…Biomineralization can be divided into three categories: (i) biologically influenced, (ii) biologically induced and (iii) biologically controlled (Dupraz et al, 2009; Görgen et al, 2021). Like photoautotrophs, heterotrophs can influence carbonate precipitation producing large amounts of negatively charged biomolecules (e.g., cell walls and EPS), which offer sites for mineral nucleation and precipitation (Braissant et al, 2003; Dupraz & Visscher, 2005; Giuffre et al, 2013; Han et al, 2019; Sánchez‐Román et al, 2007; Sánchez‐Román, McKenzie, et al, 2011; Sánchez‐Román et al, 2014; Sánchez‐Román et al, 2015; Sanz‐Montero et al, 2019; Wen et al, 2020; Zhao et al, 2023). The same mechanism is valid for negative charges on the bacterial cell wall (González‐Muñoz et al, 1996; Görgen et al, 2021; Marvasi et al, 2017; Perito et al, 2014; Sánchez‐Román et al, 2007, 2008; Sánchez‐Román, McKenzie, et al, 2009; Sánchez‐Román, Vasconcelos, et al, 2009; Sánchez‐Román, McKenzie, et al, 2011; Sánchez‐Román, Romanek, et al, 2011).…”