The importance of groundwater flow to the formation of modern thrombolitic microbialites

Abstract

Modern microbialites are often located within groundwater discharge zones, yet the role of groundwater in microbialite accretion has yet to be resolved. To understand relationships between groundwater, microbialites, and associated microbial communities, we quantified and characterized groundwater flow and chemistry in active thrombolitic microbialites in Lake Clifton, Western Australia, and compared these observations to inactive thrombolites and lakebed sediments. Groundwater flows upward through an interconnected network of pores within the microstructure of active thrombolites, discharging directly from thrombolite heads into the lake. This upwelling groundwater is fresher than lake water and is hypothesized to support microbial mat growth by reducing salinity and providing limiting nutrients in an osmotically stressful and oligotrophic habitat. This is in contrast to inactive thrombolites that show no evidence of microbial mat colonization and are infiltrated by hypersaline lake water. Groundwater discharge through active thrombolites contrasts with the surrounding lakebed, where hypersaline lake water flows downward through sandy sediments at very low rates. Based on an appreciation for the role of microorganisms in thrombolite accretion, our findings suggest conditions favorable to thrombolite formation still exist in certain locations of Lake Clifton despite increasing lake water salinity. This study is the first to characterize groundwater flow rates, paths, and chemistry within a microbialite‐forming environment and provides new insight into how groundwater can support microbial mats believed to contribute to microbialite formation in modern and ancient environments.

Extensive Polygonal Fracture Network in Siccar Point group Strata: Fracture Mechanisms and Implications for Fluid Circulation in Gale Crater, Mars

“…Local upwelling of groundwaters along the sub–Siccar Point unconformity may have even held fractures open, inhibiting fracture healing. On Earth, such fluid migration through open fractures plays a role in both the formation of tepee structures (Assereto & Kendall, ; ; Burri et al, ; Kendall & Warren, ) and the deposition of microbialites in ephemeral, desiccation‐prone lakes (Vanden Berg, ; Warden et al, ). In drier areas of the SPg, perhaps only influenced by capillary flow of fluids through the SPg sandstone, repeated cycles of desiccation would have resulted in continuous evolution of fracture patterns.…”

Microbially influenced lacustrine carbonates: A comparison of Late Quaternary Lahontan tufa and modern thrombolite from Fayetteville Green Lake, NY

“…The role of groundwater flux in modern microbialite formation has received limited attention, although groundwater may play a significant role in microbialite formation, and a large number of modern microbialites are groundwater‐associated (Warden et al, ). Many modern microbialite studies indicate groundwater discharge occurrence at the sites of microbialite formation, including the microbialites at Pavilion Lake (Russell et al, ), Lake Van (López‐García et al, ), Lake Tanganyika (Tiercelin et al, ), Cuatro Ciénegas (Breitbart et al, ), Pyramid Lake (Arp et al, ), Great Salt Lake (Bouton et al, ), and Fayetteville Green Lake (Thompson et al, ).…”

Biotic–Abiotic Influences on Modern Ca–Si-Rich Hydrothermal Spring Mounds of the Pastos Grandes Volcanic Caldera (Bolivia)

“…Accommodation space is a major driving factor, particularly in marine and lacustrine contexts, as variations in water depth constrain microbial mat development, thus affecting microbialite size and morphology [99][100][101][102]. In hydrothermal systems, accommodation space mainly depends on water discharge (i.e., hydrothermal input and rainfall) and fluid upwelling [103]. As a consequence, in palustrine domains, accommodation space is relatively low along the hydrothermal pathway of La Salsa (<10 cm, except in the central pool), limiting microbialite size to a few centimeters in height.…”

“…In hydrothermal systems, accommodation space mainly depends on water discharge (i.e. hydrothermal input and rainfall) and fluid upwelling [103]. As a consequence, in palustrine domains, accommodation space is relatively low along the hydrothermal pathway of La Salsa (<10 cm, except in the central pool), limiting microbialite size to a few centimeters in height.…”