Browsing by Author "Sarikaya, MA"

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    Carbonate and silicate intercomparison materials for cosmogenic 36Cl measurements
    (Elsevier, 2019-09-15) Mechernich, S; Dunai, TJ; Binnie, SA; Goral, T; Heinze, S; Dewald, A; Schimmelpfennig, I; Keddadouche, K; Aumaître, G; Bourlès, D; Marrero, S; Wilcken, KM; Simon, KJ; Fink, D; Phillips, FM; Caffee, M; Gregory, LC; Phillips, R; Freeman, SPHT; Shanks, R; Sarikaya, MA; Pavetich, S; Rugel, G; Merchel, S; Akçar, N; Yesilyurt, S; Ivy-Ochs, S; Vockenhuber, C
    Two natural mineral separates, labeled CoCal-N and CoFsp-N, have been prepared to serve as intercomparison material (ICM) for in situ-produced cosmogenic 36Cl and natural chlorine (Clnat) analysis. The sample CoCal-N is derived from calcite crystals in a Namibian lag deposit, while the sample CoFsp-N is derived from a single crystal of alkali-feldspar from a Namibian pegmatite. The sample preparation took place at the University of Cologne and a rotating splitter was used to obtain homogeneous splits of both ICMs. Forty-five measurements of CoCal-N (between 1 and 16 per facility) and forty-four measurements of CoFsp-N (between 2 and 20 per facility) have been undertaken by ten target preparation laboratories measured by seven different AMS facilities. The internal laboratory scatter of the 36Cl concentrations indicates no overdispersion for half of the laboratories and 3.9 to 7.3% (1σ) overdispersion for the others. We show that the CoCal-N and CoFsp-N splits are homogeneous regarding their 36Cl and Clnat concentrations. The grand average (average calculated from the average of each laboratory) yields initial consensus 36Cl concentrations of (3.74 ± 0.10) × 106 at 36Cl/g (CoCal-N) and (2.93 ± 0.07) × 106 at 36Cl/g (CoFsp-N) at 95% confidence intervals. The coefficient of variation is 5.1% and 4.2% for CoCal-N and CoFsp-N, respectively. The Clnat concentration corresponds to the lower and intermediate range of typical rock samples with (0.73 ± 0.18) µg/g in CoCal-N and (73.9 ± 6.8) µg/g in CoFsp-N. We discuss the most relevant points of the sample preparation and measurement and the chlorine concentration calculation to further approach inter-laboratory comparability. We propose to use continuous measurements of the ICMs to provide a valuable quality control for future determination of 36Cl and Clnat concentrations. © 2019 Elsevier B.V.
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    Defining denudation rate of carbonate rocks using cosmogenic 36Cl in the Taurus Mountain, S-SW Turkey
    (Copernicus GmbH, 2021-04-19) Hashemi, K; Sarikaya, MA; Wilcken, KM
    Denudation of carbonate terrains occurs by the contribution of both chemical and mechanical weathering. In-situ cosmogenic 36Cl is a robust proxy to quantify the long-term total denudation rate of carbonate rocks. In this study, we defined the steady-state denudation rate of carbonate bedrock using 36Cl for 105-106 years under the temperate Mediterranean to semi-arid climate in and around the Taurus Mountain Range, S-SW Turkey. We collected 13 samples from different lithological units; Jurassic-Cretaceous neritic limestone in the temperate western Taurus, Miocene neritic limestone in the semi-arid Central Taurus, and Mesozoic marbles in the continental part of Central Taurus. The calculated denudation rates range from 28.9 ± 1.4 mm/ka in the Mediterranean coastal range to 1.6 ± 0.1 mm/ka towards northern continental/rain shadow. We compared the denudation rates with a range of parameters such as topographic, climatic, lithologic and mechanical properties of rocks. For almost all samples denudation rate increases with elevation, with two exceptions with the highest rates despite their lower elevations. This high denudation rates could be due to their proximity to the sea. Our results showed that denudation rates decrease with increasing distance from the coast. All denudation rates showed a positive correlation with mean annual precipitation (MAP ~ 400-760 mm) as suggested by other studies worldwide. Annual temperatures (MAT ~ 6-16 °C), however, has a negative correlation with the denudation rates, i.e. the highest denudations occur in the low temperatures (MAT ~ 6-8 °C). The mechanical strength of the rocks was measured with a Schmidt hammer in the field. The high rebound values of Schmidt hammer, indicating the high mechanical strength, correlate with low denudation rates. Nevertheless, the mechanical strength of the carbonate bedrock is not as effective as precipitation or available moisture on denudation rates. This could be shown by two samples close to the Mediterranean which both have high mechanical strength nonetheless show the highest denudation rates. In conclusion, our study suggests that carbonate bedrock denudation in Taurus Mountain correlates with high elevation (~ 1900-2250 m), high precipitation (~ 700-800 mm), low temperatures (~ 6-8 °C) and short distances from the Mediterranean coast.
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    Late pleistocene cosmogenic 36Cl glacial chronology of the Mount Karanfil, Central Taurus Range, Turkey
    (American Geophysical Union, 2018-12-14) Çiner, A; Köse, O; Sarikaya, MA; Yildirim, C; Candaş, A; Wilcken, KM
    The glacial chronology of the Taurus Mountain Range of Turkey is probably one of the best studied in the world thanks to several works and publications that use quantitative methods during the last decade. Here, we report the timing of deglaciations during the late Pleistocene in the Mount Karanfil (37.36oN, 35.03oE, 3026 m) in the central Taurus Range. Glaciers that originated from N-NW facing cirques at ca. 2500 m asl, deposited lateral, hummocky and terminal moraines that reach down to 2100 m asl. We dated the limestone boulders from these moraines by terrestrial cosmogenic nuclide 36Cl surface exposure method. A total of 20 boulder ages indicate up to 3 phases of deglaciation during the late Pleistocene. Three glaciers that deposited well-developed lateral moraines ca. 1.5 km long and up to 50 m high, yield an average mean age of ∼20 ka corresponding to the local Last Glacial Maximum (LGM). Another moraine, at slightly higher elevations, testifies to the presence of Late Glacial (∼15 ka) in the Mount Karanfil. Finally, a lower cirque moraine, in contact with the upper parts of the Late Glacial moraines at ∼2200 m asl, yielded an age of 10.5 ± 1.0 ka, which indicates that glaciers totally disappeared at the onset of Holocene. A rock glacier at ca. 2500 m was also dated to early Holocene (11.5 ± 1.1 ka) indicating that in early Holocene periglacial conditions dominated in the area. The moraine and rock glacier ages are first dates obtained from this part of the Taurus Range and are compatible with glacial chronology of the southern Turkey and surrounding regions.