Modelling size constraints on carbonate platform formation in groundwater upwelling zones

Abstract

Carbonate depositional systems related to groundwater upwelling are ubiquitous around the world and form ecologically and culturally important features of many landscapes. Spring carbonate deposits record past climatic and hydrological conditions. The reconstruction of past processes using spring carbonate proxies requires fundamental understanding of the factors that control their geometry. In this work, we show that the spatial extent of spring carbonate platforms is amenable to quantitative prediction by simulating the early growth stage of their formation for the iconic mound springs in the central Australian outback. We exploit their well-defined, circular geometry to demonstrate the existence of two size-limiting regimes: one controlled by the spring flow rate and the other by the concentration of lattice ions. Deviations between modelled and observed size metrics are attributable to diminishing spring flow rates since formation, enabling assessment of the relative vulnerability of springs to further hydrological change.

Crystallization pathways in the Great Artesian Basin (Australia) spring mound carbonates: Implications for life signatures on Earth and beyond

“…In present day conditions, precipitation of carbonates occurs at near-ambient water temperatures of ca 15 to 30°C (Keppel et al, 2011(Keppel et al, , 2012(Keppel et al, , 2018. The average annual rainfall is ca 125 mm year À1 (Keppel et al, 2012).…”

“…1B), has several large active and inactive mounds, including two of the largest mounds in the region; 'The Bubbler' and 'Blanche Cup' (e.g. Prescott & Habermehl, 2008;Keppel et al, 2018). The Bubbler has an overall surface of ca 38 500 m 2 (including surrounding wetlands; Keppel et al, 2012) and a mound radius of 39.7 m (Keppel et al, 2018).…”

“…Prescott & Habermehl, 2008;Keppel et al, 2018). The Bubbler has an overall surface of ca 38 500 m 2 (including surrounding wetlands; Keppel et al, 2012) and a mound radius of 39.7 m (Keppel et al, 2018). Blanche Cup consists of prominently layered spring carbonates and pool deposits ( Fig.…”

“…In the Warburton and Beresford Spring area (Fig. 1B) there is only one active spring (Warburton mound; Keppel et al, 2018), which is surrounded by macrophytes (Fig. 2J).…”

“…Hydrochemistry of the Great Artesian Basin (GAB) spring water. From Keppel et al (2011Keppel et al ( , 2018 mound in Table 1). This complex covers an area of ca 2.4 km 2 with mound diameters ranging from a few metres to up to 40 m. The largest active mound is located in the northern part of the region (StSp 3; Table 1).…”