What Causes Carbonates to Form “Shrubby” Morphologies? An Anthropocene Limestone Case Study

What are the different styles of calcite precipitation within a hyperalkaline leachate? A sedimentological Anthropocene case study

“…Similar to the sparry fabrics reported by Bastianini et al (2019), the sparry carbonate microfacies consists of globular arrangements of isopachous fans within 500 µm to 2 mm thick crusts made up of milky white to pale brown calcite (Figure 8A,B). The colour differences in the laminae might be explained by oxidation/reduction conditions changing during spar growth resulting in more or less Mn or Fe trapped in the calcite lattice.…”

“…This microfacies is here referred to as delicate filamentous structures (ranging from 100 to 2,500 µm in length) coated by translucent white euhedral to anhedral calcite crystals (Figure 7A). In some adjacent areas, carbonate grains are clearly detached from microbial filaments forming intraclastic accumulations (Figure 7B) already described in Consett (see Figure 7B and cluster‐shaped carbonates in figure 11 from Bastianini et al, 2019).…”

“…The crystal shrub fan microfacies consist of light grey‐white botryoidal crystal fans 1–3 mm in height and stacked on each other as inverted cones growing on top of discontinuous horizons (Figure 10A through D) (compare with shrub facies in Bastianini et al, 2019, their figure 10). Botryoids are internally composed of very coarse subhedral to euhedral, elongated rhombohedral crystals forming bladed aggregates (60 µm in length) (Figure 10A through D) with their c ‐axis radiating from a previous substrate (Figure 10A through D).…”

“…Shrub bifurcations tend to be more developed in terminal stages where individual shrub branches show more defined limits and sometimes the presence of trapped or infiltrated organic matter (Figure 10A,B). A black degraded biofilm and some diatoms are found surrounding the crystals (Bastianini et al, 2019). Dendrite carbonates are light grey, tree-shaped calcite polycrystals showing multiple levels of branching (Figure 11A through D, see also Bastianini et al, 2019, their figure 9).…”

The mantle, CO2and the giant Aptian chemogenic lacustrine carbonate factory of the South Atlantic: Some carbonates are made, not born

“…In addition, considering the abundance of calcite precipitates, ooids are extremely rare. A likely explanation is that carbonate nucleation was suppressed by kinetic inhibition favouring growth at existing sites (Wright & Tosca, 2016; see also Bastianini et al ., 2019).…”