Abstract
Travertines and calcareous tufa are porous deposits formed by interactions between ambient precipitation of calcium carbonate and resident organisms under different temperature regimes. The distinctions between travertine as thermal spring deposits and calcareous tufa (Kalktuff) as deposits in the springs and rivers at ambient temperatures are fluid. Both represent end points in bio- and physico-chemical calcification processes across a broad gradient of temperature, mineral composition and ion saturation levels. Ecological preferences of micro- and macroorganisms in travertine depositional systems result in the re-distribution of water flow, modification of the landscape and its ecology. The resulting sedimentary structures include new environmental settings with different and diversified biota. They also include different microenvironments of diagenesis with different timings of the processes involved. Conditions in modern ambient temperature travertines of the Plitvice system of lakes and waterfalls are compared with the similar, ancient system of Rocchetta a Volturno, in the central Apennines. Diagenetic alterations are described and illustrated starting with biologically identified primary deposits.
Highlights
The term travertine has been used for centuries for porous building stone, desirable for its structural quality especially for the construction of vaults and arches (PENTECOST, 2005)
In thermal deposits, where precipitation is rapid, the porosity is produced by the trapped gas and by micrometer sized organisms embedded into the deposit
Carbonate precipitation predominates, guided by differential degassing, evaporation and cooling, favouring precipitation where the water is in direct contact with the atmosphere
Summary
The term travertine has been used for centuries for porous building stone, desirable for its structural quality especially for the construction of vaults and arches (PENTECOST, 2005). The porous stone of Tivoli is still being quarried today, most of it originating from thermal springs of the area. The use of the name in geology has often been associated strictly with thermal spring deposits, whereas its ambient water counterpart is usually referred to as calcareous tufa (German: Kalktuff, Croatian: sedra). This distinction is difficult to maintain, because hydrothermal springs, range in temperature, and so do the processes of mineral precipitation. Travertine as building stone includes both hot spring and ambient temperature deposits. Deposition of travertines and calcareous tufa in the region occurred at different times during interglacial and postglacial periods and remained
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