Relative influence of biotic and abiotic processes on travertine fabrics, Satono‐yu hot spring, Japan

Abstract

The relative influences of biotic and abiotic processes on travertine fabrics are still not well understood, despite increasing interest in the last decade to better understand the record of ancient microbial life and sedimentary fabrics in microbial hydrocarbon reservoirs. This study examines travertines at Satono‐yu hot spring in Japan (the temperature of water flowing over the travertine was ca 35°C), to better understand the interaction between depositional, hydrochemical and microbial parameters at different flow settings. Characteristics of the bulk hydrochemistry, mineralogy (exclusively aragonite) and the driving force for precipitation (primarily abiotic CO2 degassing with some photosynthetic microbial contribution) were similar among all of the flow settings. Conversely, the increase in flow velocity suppressed the influence of photosynthesis and enhanced the abiotic precipitation due to the thinner diffusive boundary layer at the travertine surface–water interface. Additionally, the increase in flow velocity changed the microbial composition and decreased the bacterial diversity by reflecting their adhesion efficiency on the travertine substrate. The acidity of the cyanobacterial sheaths controls the aragonite nucleation rate and the resulting calcification, even at significantly high equilibrium CO2 partial pressure (ca 22 to 28 matm), high dissolved inorganic carbon concentration (ca 35 to 38 mmol l−1), and elevated aragonite saturation state (ca 20‐fold to 34‐fold). Therefore, the increase in flow velocity suppresses the microbial influence with respect to the increase in the saturation state, the nucleation site supply and pore space generation. Overall, this results in the predominance of abiotic precipitation under high flow velocities. Consequently, a sparse‐micritic fabric with abundant interlamina porosity forms under lower flow velocity where the microbial influence is effective, while a dense‐sparitic fabric with little inter‐crystalline porosity forms under higher flow velocity where abiotic precipitation prevails. These findings provide an essential base for assessing the formation processes of ancient travertines and comparable deposits from petrological fabrics.

The influence of microbial mats on travertine precipitation in active hydrothermal systems (Central Italy)

“…This study identifies three temperature-controlled microbial communities and related carbonate facies: a) high temperature (50-55°C in Bullicame, 44-49°C in Bollore) streamers with sulphide oxidizing bacteria and/or green non sulphur Chloroflexus anoxygenic phototrophs associated with sulphate reducing bacteria and rod-shaped cyanobacteria Synechococcus ; b) intermediate temperature (<50°C in Bullicame, 40-44°C in Bollore) crystalline and clotted peloidal micrite dendrites, rafts and coated bubbles with cyanobacteria dominated by Spirulina , possible Synechococcus and other filamentous Oscillatoriales (possible Oscillatoria , Phormidium ); c) low temperature (34-33°C in Gorello Waterfall) laminated boundstone and coated grains with high diversity of Oscillatoriales filamentous cyanobacteria (possible Oscillatoria , Phormidium , Lyngbya , Leptolyngbya , Schizotrix ) associated with Spirulina , possible Nostocales ( Nostoc , Anabaena , Pseudoanabaena , Calothrix , Fischerella ), and diatoms as observed in the numerous reported studies about hydrothermal terrestrial spring deposits (cf. Pentecost and Tortora, 1989; Ward et al, 1998; Pentecost, 2003; Norris et al, 2002; Sompong et al, 2005; Norris and Castenholz, 2006; Pentecost et al, 2007; Roeselers et al, 2007; Okumura et al, 2013; Roy et al, 2014; Smythe et al, 2016; Sugihara et al, 2016; Shiraishi et al, 2019). These temperature controlled microbial communities are similar to those proposed by various authors for the Yellowstone National Park springs (Cady and Farmer, 1996; Farmer; 2000; Fouke, 2011; Des Marais and Walter, 2019).…”

“…Pentecost, 2003). Most of these inferred cyanobacteria forms have been identified in moderate temperature (20-50°C) hydrothermal systems associated with diatoms (Pentecost, 2003; Shiraishi et al, 2019; Gong et al, 2020). In particular, Calothrix thermalis has been described in various hydrothermal vents with temperature of 20-40°C (Cady and Farmer, 1996; Farmer, 2000; Pentecost, 2003, 2005; Jones and Peng, 2015).…”

Carbonate tufas as archives of climate and sedimentary dynamic in volcanic settings, examples from Gran Canaria (Spain)

“…On the other hand, the dendrite crusts formed under very high precipitation rates (Jones & Renaut, 2010; Gandin & Capezzuoli, 2014) and they were later degraded by microbes (Camuera et al ., 2014). This suggests that, during dendrite growth, precipitation rates exceeded the ability of microbes to colonize the surface and develop stromatolite lamination (Rodríguez‐Berriguete & Alonso‐Zarza, 2019; Shiraishi et al ., 2019). The possible environmental factors leading to a decrease in calcite precipitation rate allowing formation of stromatolites can be a decrease in CO 2 degassing rates and/or waters less saturated in calcite.…”

Influence of biotic vs abiotic processes on the genesis of non‐marine carbonates along the Cameroon Volcanic Line (Cameroon) and palaeofluid provenance

“…In this work, petrography and geochemistry of spring carbonates from the Cameroon Volcanic Line (CVL) from the Ngol and Bongongo areas (Figure 1) are investigated to identify the processes that induced their precipitation and the provenance of the parent fluids. These carbonates formed from springs of hydrothermal water with temperature above 30°C and are, therefore, considered as travertines (Capezzuoli et al, 2014;Pentecost, 1990;Shiraishi et al, 2019). The occurrence and bulk composition of travertines from Bongongo and Ngol were presented for the first time by Le Maréchal (1971Maréchal ( , 1976) and more recently by Bisse et al (2018).…”

“…It is now clear that, in order to use carbonates as reliable geochemical proxies, it is crucial to distinguish between inorganic vs biomediated mechanisms of mineral precipitation (Chafetz & Guidry, 1999; Pentecost, 1990; Shiraishi et al, 2019). The accuracy of spring carbonates as archives of palaeoenvironmental information depends on their mode of formation and the interplay of abiotic and biotic processes (Brasier, 2011; Della Porta, 2015 for a comprehensive review).…”