Ancient Modeling of Hydrology Based on Comparison of δo18 Carbonate and the δo13 Crbonate Parishan Lake (Fars Province)

stable isotopes are strong tools for environmental studies, because most of the elements are naturally more abundant at least in one isotope. Among the studies, many researchers have considered the Carbon (C13/C12), Oxygen, (O18/O16) Hydrogen (H2/H) and Nitrogen (N29/N28) which remain effects on the organic (plants and animals) and inorganic (water, soils, rocks, fossils,…) material (Griffiths, 1998, p47). In order to study the Carbon and Oxygen stable isotopes of the lake carbonates, recognizing the effective factors on the isotope's value and identifying the relationship between the isotope values is essential. In the lake environments many factors can determine the variability of the Oxygen isotopes of the lake sediments which the most important of them are including: source of materials, water temperature, residence time and the input and output amount of the lake (Benson et al, 1996, p747). In the open hydrological systems, the Oxygen isotope components of the lake water dominantly reflect the isotopic components of precipitation (rain and snow) (Leng& Marshal, 2004, p817). In addition to the effective factors on the isotopic amount of carbon and oxygen, the relationship between the carbon and Oxygen isotopes in lake systems can deliver valuable information about the history of the lake's hydrology. The relationship between the isotope values of carbon and oxygen isotopes in the closed lakes can be based on the hydrological changes, evaporation, biomass production and the Co2 concentration (Le and Ku, 1997, p72). There are big hydrological closed lakes especially in the arid regions, which both carbon and oxygen isotopic values are positively high. In these cases, it shows a close value of correlation. the magnitude of the correlations can be used to estimate the closeness of the lakes in different time periods. In the closed lakes, the covariance of carbon and oxygen isotope values generally indicate the interaction of carbon and oxygen isotopes with the atmosphere (Tanner, 2009, p210). In fact, the strong correlation between the carbon and oxygen isotope values indicates a common effective mechanism on the lake dissolved inorganic carbon (DIC) (Eastwood et al, 2007, p239). In the open lakes, there is a prefencally weak correlation between the carbon and oxygen isotope values. In fact, generally, the the strong correlation between the carbon and oxyegen isotope values ocuurs in the lake that have a long residence time. The correlation values more than 0.7 indicate the lake carbonates deposited in a hydrological closed lake. Furthermore, in these cases, due to the high variability of the lake water, the oxygen isotope values in the closed lake are approximately around 0.0 %. Therefore, this covariance could be used to estimate the closeness of the lakes with the carbonates deposition (Talbot, 1990, p273). Based on the methods mentioned above, a core was taken from Parishan lake in Fars. The aim of this research is to reconstruct the hydrological condition of the lake in the past using the Carbon and Oxygen stable isotopes of the Ostracoda microfossil.