Proxy Records of Terrestrial Carbonates for Palaeoclimatic Implications during the Middle-Late Pleistocene: A Case Study of the Sarıkavak Tufas (Afyon, SW-Türkiye)

Terrestrial carbonates such as travertine, tufa and speleothem are quite sensitive for climatic fluctuations. By determining radiometric dating (U/Th, ۱۴C), stable isotope (δ۱۳C and δ۱۸O), and palynomorph results besides to sedimentological properties of terrestrial carbonates (lithotypes, depositional processes, etc.) as proxy records, we can insight into palaeoclimatic history of the Quaternary period. In this study, the dating and pollen records from Sarıkavak tufas, (Afyon) SW-Türkiye, together with lithofacies descriptions, geochemical and petrographic results have been obtained from the drilling cores. Sarıkavak tufas, which crop out on the northern edge of the NE-SW trending Acıgöl Graben, were examined in detail. These terrestrial carbonates were precipitated in the fluvio-palustrine environment, and they formed in high-gradient and stepped fluvial conditions representing barrage-dammed and terrace-slope systems. Cascade tufa formation at the graben border presents a very significant appearance in the study area. Their lithofacies are moss tufa included macrophytes, bryophytes and vertical stems, phytoclastic tufa, peloidal tufa, micritic tufa, algal tufa, intraclastic tufa, extra-formational tufa, conglomerate-sandstone, lime-muddy clay and palaeosol level, in respectively. According to the U/Th ages obtained from the tufas, it is clearly said that tufa deposition in this region ceased approximately ۸۰±۱.۵ kyr ago. Stable isotopic results show less negative and more positive carbon values (between -۱.۶۳ and +۱.۵۴ ‰ V-PDB) while oxygen stable isotopes have more negative values (between -۷.۴۹ and -۱۰.۸۳ ‰ V-PDB). The carbon isotopic results could be related to the progressive downstream CO۲ degassing from host rocks, enhanced by high-velocity current conditions, changes in the soil-CO۲ contribution and photosynthesis. The fluctuations of oxygen isotopes are most probably related to variable effects of evaporation in depositional environment. Both carbon values and palynological findings show that drought conditions were dominantly present in the Pleistocene period, but in some cases drought conditions decreased depending on the amount of rainfall. The increasing amount of gymnosperm pollen is more likely to appear in more humid conditions due to the decreasing of drought condition in this time interval.

کلیدواژه ها:

Terrestrial carbonates ، Palaeoclimate ، Palaeoenvironment ، Pleistocene ، SW-Türkiye