Sedimentology of Travertine

Sediment bodies of travertine exhibit unique geomorphology that results from its rapid sedimentation rate. As described in Chap. 2 and will be discussed in Chap. 6, the rapid sedimentation rate is closely associated with rapid CO2 degassing from water, which elevates the level of supersaturation with respect for CaCO3. Intensity of the CO2 degassing is generally related with hydrological conditions: more CO2 degassing in turbulent conditions. Therefore, rapidly flowing water is a site of active deposition in travertine settings. This is a distinct difference from an ordinary fluvial sedimentary system, in which rapidly flowing water generally erodes sediment. In travertine systems, erosion is an unusual process unless flow rate is excessively developed by some reasons like flooding. In our study in Pancuran Pitu in Indonesia, a flow rate of 2 m/s is not enough to erode travertine (Okumura et al. 2012). Initially depressed watercourse is filled up, and the watercourse shifts to flow along a newly developed depressed route (Fig. 3.1). Sedimentation of travertine usually occurs at the interface of water and sediment substrate. The substrate is normally preexisted travertine but can be sedimentary grains. Mode of sedimentation is therefore accretion of newly precipitated crystals of calcite or aragonite and somehow similar with coral reef crest where a sediment body grows forward by mineral secretion of reef corals.