Depositional system and palaeoclimatic interpretations of Middle to Late Pleistocene travertines: Kocaba, Denizli, south-west Turkey

Abstract

Travertine deposits in western Turkey are very well-exposed in the area of Kocaba, in the eastern part of the Denizli Basin. The palaeoclimatic significance of these travertines is discussed using U/Th dates, stable isotope data and palynological evidence. The Kocaba travertine occurrences are characterized by successions of depositional terraces associated with palaeosols and karstic features. The travertines have been classified into eight lithotypes and one erosional horizon, namely: laminated, coated bubble, reed, paper-thin raft, intraclasts, micritic travertine with gastropods, extra-formational pebbles and a palaeosol layer. The analysed travertines mostly formed between 181ka and 80ka (Middle to Late Pleistocene) during a series of climatic changes including glacial and interglacial intervals; their C-13 and O-18 values indicate that the depositional waters were mainly of basinal thermal origin, occasionally mixed with surficial meteoric water. Palynological results obtained from the palaeosols showed an abundance of non-arboreal percentage and xerophytic plants (Oleaceae and Quercus evergreen type) indicating that a drought occurred. Marine Isotope Stage 6 is represented by grassland species but Marine Isotope Stage 5 is represented by Pinaceae-Pinus and Abies, Quercus and Oleaceae. Uranium/thorium analyses of the Kocaba travertines show that deposition began in Marine Isotope Stage 6 (glacial) and continued to Marine Isotope Stage 4 (glacial), but mostly occurred in Marine Isotope Stage 5 (interglacial). The travertine deposition continued to ca 80ka in the south-west of the study area, in one particular depression depositional system. Palaeoenvironmental indicators suggest that the travertine depositional evolution was probably controlled by fault-related movements that influenced groundwater flow. Good correlation of the stable isotope values and dates of deposition of the travertines and palynological data of palaeosols in the Kocaba travertines serve as a starting point for further palaeoclimate studies in south-west Turkey. Additionally, the study can be compared with other regional palaeoclimate archives.