Introduction to tufas and speleothems - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 2

Fig. 1. A schematic diagram of terrestrial carbonate precipitation occurring within an interlinked system. This continuum exhibits dominantly physico-chemical processes at one extreme (speleothems, on the left of diagram
, and travertines, on the right) and dominantly biological processes at the other (oncoid and lake carbonates). Tufa systems typically fall within
the middle of this continuum, exhibiting both physical and microbial control. When calcite saturation no longer allows tufa framework development, oncoids typically are developed (top right, showing cross section of oncoid
with stromatolitic structure as inset). All these deposits properly should be considered as part of the same depositional system within karst environments, with individual occurrences related to the position of the hydrochemical 'knick-point', that is, when precipitation activation energy is breached by local biological influences.