, Volume 29, Issue 1, pp 251-263

Microbial origin of travertine fabrics—two examples from Southern Germany (Pleistocene stuttgart travertines and miocene riedöschingen Travertine)

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Summary

In Southern Germany, two examples of travertines of different age and depositional morphology were examined in detail. Travertines are laminated carbonate rocks formed by precipitation from mineral and/or thermal waters. They include characteristic facies types, such as bushy layers (‘shrubs’) referred to calcification of branching microbes (‘Dichothrix’-morphotype), laminar microbial mats, peloidal layers, and gas bubble layers formed within the sediment. In travertines, microbial activity is the most important factor for carbonate precipitation.

Tufas differ from travertines by their abundance of molds of higher plants (leaves, reed, moss, green algae). They may be associated with travertines, but do not exhibit strict travertine facies types. Tufas are common in normal fresh water environments. Contrary to travertines and tufas, calcareous sinters usually occur in restricted areas like spring fissures, caves, or in pores, where microbial activity is not totally absent, but not of paramount importance for precipitation.

Pedogenetic processes, which can alter travertine deposits, are responsible for large-scale features such as tepee-structures, and some intraclastic layers, and microscopic structures like endolithic borings andMicrocodium. Travertines may also grade into lacustrine limestones with Characeae, ostracods, and aquatic gastropods.