Depositional and geochemical characteristics of geomorphologically controlled recent tufa deposits on the Göksü River in Yerköprü (Konya, southern Turkey)

Abstract

Recent tufa deposition has been taking place on a 500 m-long natural bridge on the Goksu River in the Yerkopru region, southern Konya, Turkey. The Karasu spring arises from the Karasu normal fault, flows over this natural bridge and drops down from the end of the bridge, forming a spectacular waterfall. There is a dense CO2 degassing from this water and the H2CO 3 −1 content is 506,3 mg/L at the orifice and 549 mg/L on the waterfall, but it drops almost to half at the bottom of the waterfall. The field observation and chemical data showed that the deposition of the studied tufa was related only to the water derived from the Karasu spring. At the active waterfall area, tufa deposition takes place on the cascade, in small and large ponds and in channels. People living in the area build canals for irrigation and milling purposes, which cause the spreading of tufa deposits to other than the main course of the Karasu spring water. The most common types of facies are the different phytotherm facies, but stromatolitic, micritic and phytoclastic facies are also present to a lesser amount. The δ13C content of the tufa deposits ranges from 1,6 to − 3,3 and δ18O contents from − 9,6 to − 11,5. The higher δ13C values of the Yerkopru tufa deposits indicate that the carbonate-rich water of the Karasu spring originated from a carbonate aquifer. The isotopic values of the studied tufa samples are similar to those of travertine, but the Karasu water is interpreted as cold water. Therefore, it may be considered as “travitufa”.