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    Depositional Properties and Paleoclimate of a Middle-Upper Pleistocene Fan Delta Sequence in the Bor Plain, Central Anatolia, Turkey
    (Istanbul Univ, Fac Letters, Dept Geography, 2024) Bayer-Altin, Turkan; Karakas, Zehra Semra; Altin, Bekir Necati; Kayseri-Ozer, Mine Segul
    The Bor Plain, which is located in the Middle Kizilirmak subregion of the Central Anatolia Region, extends 14 km toward the west of Nigde. The fan delta deposition system in the southwest of the Bor Plain was formed on the fault-controlled foothills of Mt. Keciboyduran. The fandelta sequence shows that a paleolake formed during a phase because of the mineralogical content and frequently changing facies. Additionally, clay minerals and herbaceous plants reflecting humid and arid climatic conditions illustrate the lake-level changes. Six changes in the lake level occurred from marine isotope stage (MIS) 7 to (MIS) 5. Three major high stands occurred in the paleolake at the lowest and middle parts of the sequence. The first high stand was a stepwise transgression between similar to 240 and similar to 230 ka., and the second high stand was between similar to 200 and similar to 195 ka. The third high stand was characterized by a short transgression at 182 ka. After this stage, the lake receded significantly at 127 and 105 ka, indicating climatic control over the water level changes. In the transition from the Middle to Late Pleistocene, a revival of volcanic activity in the Leskeri monogenic volcanic mass released volcanic material, affecting sedimentation. Volcanic rocks increase dramatically in the upper section of the fandelta during an interval that coincides with low lake-level fluctuations.
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    Evolution of Drought Climatology and Variability in the Central Anatolia Region, Turkey, for the Period 1970-2020
    (Springer Basel Ag, 2023) Bayer-Altin, Turkan; Turkes, Murat; Altin, Bekir Necati
    In this study, drought climatology and drought variability in the continental semi-arid and dry sub-humid Central Anatolia Region were analyzed using the annual and seasonal precipitation totals, Aridity Index (AI) and Standardized Precipitation Index (SPI), along with the long-term trends in their time-series. Trends in precipitation totals, 12-month SPI and annual AI series were statistically determined by applying the Mann-Kendall rank correlation test (M-K test) and its sequential analysis. The climatological probability of drought and wet events was evaluated according to different classes in the region. Annual AI values indicate that dry sub-humid climate was dominant from the mid-1990s to mid-2000s, and then semi-arid conditions were dominant from the mid-2000s to recent years. The climatological probability of monthly SPI values being severely dry is dominant mostly in the semi-arid and dry sub-humid central, south and east districts of the region. According to the M-K test, statistically significant decreasing trends were determined for annual total precipitation and the 12-month SPI series in Keskin, Pinarbasi, Sariz, urgup and Aksehir. Nonsignificant and statistically significant decreasing trends in spring precipitation were determined at approximately 67% of the stations and at Ilgaz, Kulu, Eskisehir, Keskin, Zara, urgup and Sariz stations, respectively. With respect to the desertification in the Central Anatolia Region, the most vulnerable subregions for desertification processes are the Konya subregion and the Upper Kizilirmak subregion, mainly characterized by semi-arid and dry sub-humid environmental conditions.
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    Evolution of long-term trends and variability in air temperatures of Kazakhstan for the period 1963-2020
    (Springer Wien, 2024) Bayer-Altin, Turkan; Sadykova, Damezhan; Turkes, Murat
    The annual, seasonal, and monthly trends of air temperatures were analyzed for thirteen urban and five rural meteorological stations in Kazakhstan for the 1963-2020 period. The non-parametric Mann-Kendall (M-K) rank correlation and Sen's slope estimator methods and the parametric least-squares linear regression (LSLR) were used to determine whether there were positive or negative statistically significant trends in mean, average maximum, and minimum air temperature time series along with diurnal temperature ranges (DTRs), and temperature differences between five large and small cities. In addition, Kazakhstan's annual and seasonal air temperature series were analyzed in terms of autocorrelation (serial correlation) coefficients. Coefficients of variations indicated that mean annual temperature variability is the highest in northern cities. Results of the M-K trend test indicated that the highest and lowest increases in the mean air temperatures were observed in spring and autumn, respectively. The magnitudes of the significant increasing trends in annual air temperature ranged between 0.23 & DEG;C/decade at Karagandy and 0.54 & DEG;C/decade at Kyzylorda. Annual and seasonal diurnal temperature ranges (DTRs) reveal insignificantly decreasing and increasing trends at most of the stations characterized by urbanization. According to the results of both M-K and LSLR tests, annual and winter air temperature differences of some station pairs tend to significantly increase, which may mean that the differences in the calculated temperature range between large and small cities might have widened significantly. However, significance test for the calculated autocorrelation coefficients of the annual and seasonal air temperature data showed that most of the series clearly appear as a low-frequency variability on the significantly increased long-term averages.