Comparison of the Quaternary travertine sites in the Denizli extensional basin based on their depositional and geochemical data

In the Denizli Basin (Turkey), located in the western Anatolian extensional province, travertine and tufa deposition has been an ongoing process for at least 600,000 years. Travertine bodies, which are 30 to 75 m thick and each covers areas of 1 to 34 km(2), are up to 1 km(3) in volume. Today, spring waters in this area have temperatures of 19 to 57 degrees C, are of the Ca-Mg-HCO3-SO4 type in the Pamukkale, Kelkaya and Pinarbasi areas and the Ca-Mg-SO4-HCO3 type at Cukurbag. Thermal waters along the northern margin of the basin are generally hotter than those in the east-southeast and south. The delta O-18 and delta D values of the spring waters indicate a meteoric origin. The average temperatures of the hydrothermal systems in the Denizli Basin appear to have decreased from Pleistocene to Holocene. Travertine, which formed from the hotter water, is more widespread than the tufa that formed in the cooler spring waters. Deposition of the travertine, which formed largely on slopes, in depressions, and along fissure ridges (mostly on northern basin margins), was controlled by the interplay between various intrinsic and extrinsic parameters. The travertines are formed largely of calcite with only minor amounts of aragonite in some of the vertically banded, crystalline crust, raft and pisoid travertines found in some of the northern sites. The aragonitic samples, rich in Sr, are typically found around the spring orifices and along the central axis of the fissure ridges. The stable isotope values of the travertine found in the northwest and southeast parts of the basin are different. The delta C-13 values of the northern travertine deposits are more positive (3.7 to 11.7 parts per thousand. VPBD) than those found in the south-southeast areas (-4 to 5.8 parts per thousand VPDB). In contrast, the travertine and tufa in the southeastern areas have higher delta O-18 values (-15.2 to 7.8 parts per thousand VPDB) than those of the northern areas (-16.6 to -4.8 parts per thousand VPDB). Available evidence indicates that spring activity and associated travertine precipitation in the Denizli Basin were controlled largely by tectonic activity rather than by climatic conditions. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.