A rare landform: Yerköprü travertine bridges in the Taurids Karst Range,Turkey

Two examples of travertine bridges are observed at 8 to 15 m above stream level in the Lower Zamanti Basin, Eastern Taurids, Turkey. Yerköprü‐1 and Yerköprü‐2 bridges are currently being deposited from cool karstic groundwaters with log P_CO2 > 10^?2 atm. The surface area and the total volume of travertine in Yerköprü‐1 bridge are 4350 m² and 40 000 m³, whereas the values for Yerköprü‐2 are 2250 m² and 20 000 m³, respectively. The interplay of hydrogeological structure, local topography, calcite‐saturated hanging springs, algal activity and rapid downcutting in the streambed appear to have led to the formation of travertine bridges. Aeration through cascades and algal uptake causes efficient carbon dioxide evasion that enhances travertine formation. Algal curtains aid lateral development of travertine rims across the stream. Model calculations based on a hypothetical deposit in the form of a half‐pyramid implied that lateral development should have occurred from both banks of the stream in the Yerköprü‐1 bridge, whereas one‐sided growth has been sufficient for Yerköprü‐2. The height difference between travertine springs and the main stream appears to be a result of Pleistocene glaciation during which karstic base‐level lowering was either stopped or slowed down while downcutting in the main stream continued. Copyright © 2002 John Wiley & Sons, Ltd.