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Late Pleistocene calcretes from Central Anatolia(Lakes Eymir and Mogan, G?lba?? Basin): Comparison to Quaternary calcretes from Turkey

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Journal of Earth Science 2016年第5期27卷 874-882页

作者： Ceren Kücükuysal Mugla Sitki Kocman University Engineering Faculty Department of Geological Engineering Kotekli 48000 Turkey

This study is the first to report the radiocarbon ages, mineralogical, morphological, geochemical and stable isotope compositions of calcretes from Neogene sediments around lakes Eymir and Mogan in the G？lba？？ Basin of Central Anatolia. Morphologically different forms of calcretes in the G？lba？？ Basin include powdery, nodular, fracture infill, laminar and hardpan types. Calcite is the dominant mineral of calcrete compositions; the diagnostic features of dessication cracks, random fractures, Mn O linings and dense sparitic infillings are observed. Chemical analyses show arid conditions with mean annual precipitation of 〈50 mm. δ13C compositions of the calcretes range from-6.77‰ to-9.32‰ PDB, typical for most pedogenic calcretes, reflecting the development under seasonally arid climates and C3-dominated vegetation cover. δ18O values are between-5.57‰ and-7.80‰ PDB, indicating the formation from meteoric water in a vadose zone environment. The results suggest that the Middle Pleistocene was arider and warmer, favouring the formation of palygorskite in association with the different forms of calcrete occurrences, whereas the Late Pleistocene was dryer and cooler, supporting the development of calcretes.

关键词： calcrete micromorphology stable isotopes mineralogy Central Anatolia.

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Age Estimation of Qash Qooly Valley in Dokan Vicinity, North Iraq Using Exposure Age Determination Method

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Journal of Civil Engineering and Architecture 2015年第1期9卷 90-103页

作者： Varoujan K. Sissakian Nadhir Al-Ansari Sven Knutsson Private consultant Erbi114006 lraq Department of Civil Environmental and Natural Resources Engineering Lulea University of Technology Lulea 97187 Sweden

Qash Qooly valley runs parallel to Pera Magroon, Sara and Surdash anticlines, almost in SE-NW trend, and merges with the Lesser Zab River 9 km southeast to Dokan town. Before its development, it was a large basin with width ranges between 2-3 km, which was filled during Pleistocene or may be Late Pliocene by different types of sediments. The presence of the calcrete on the top indicates a wet period that has lasted for a long time as indicated from the thickness of the calcrete and alluvial fan sediments. The age of Qash Qooly valley was estimated using the exposure age determination method. The type of the sediments, their thicknesses, and erosion intensity and sediments＇ dens dissection by rills were the main features used. This study concluded that the age of the basin is Pliocene--Late Pleistocene, whereas the valley started to be developed during uppermost Late Pleistocene and is still active in shifting its course.

关键词： Pleistocene alluvial fans piedmont calcrete active erosion.

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