Paleoenvironmental Records of Calcrete in the Three Gorges of Yichang,China

Calcretes occur in a number of locations across the Yangtze Three Gorges in Yichang,central China. They represent the phase of Quaternary calcium carbonate cementation affected by the East Asian monsoon region.Calcretes are situated at the relict fluvial terrace that were deposited within confined bedrock and limestone soil.Eight samples from separate terrace were singled out and dated by ESR.

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

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

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.

Issues and Limitations of Broad Band Remote Sensing of Kimberlite—A Case Example from Kimberlites of Dharwar Craton, India

Present study attempts to understand the potential of multispectral ASTER (Advanced space borne thermal emission and reflection radiometer) data for spatial mapping of kimberlite. Kimberlite is an economic rock known for hosting diamond. Kimberlite also has petrogenetic importance for giving us clue on the composition of lower part of the mantle. Kimberlites often contain serpentine, carbonate minerals;which have their diagnostic spectral signatures in short wave infrared (SWIR) domain. In the present study, attempt is made to delineate kimberlite from adjacent granite-granodiorite gneiss based on processing of the ASTER data as ASTER’s spectral channels can detect some of the diagnostic absorption features of kimberlites. But it has been observed that the kimberlites are difficult to be delineated by processing the ASTER data using correlative information of both sub-pixel and per-pixel mapping. Moreover, smaller spatial size of kimberlites with respect to pixel size of ASTER SWIR channels further obscures the spectral feature of kimberlite. Therefore, an attempt is also made to understand how intra pixel spectral mixing of kimberlite and granite granodiorite-gneiss modifies the diagnostic spectral feature of kimberlite. It is observed that spectral feature of kimberlites would be obscured when it is has very small spatial size (one-tenth of pixel) with respect to pixel size. Moreover, calcrete developed in the adjacent soil has identical absorption feature similar to the spectral features of kimberlites imprinted in the respective ASTER convolved spectral profiles. This also has resulted false-positives in ASTER image when we use spectral feature as a tool for spatial mapping of kimberlite. Therefore hyperspectral data with high spatial and spectral resolution is required for targeting kimberlites instead of using broad band spectral feature of kimberlites.

Quantitative Geomorphological and Hydromorphometric Analysis of Drainage Basins of As Sabriyah (Kuwait) Using GIS Techniques

A well-developed drainage network was carved in the study area in a hard calcretized and gypcretized gravelly sand of the Dibdibba Formation (Al-Rukham slope) in pluvial episodes in the post-pleistocene age, and is referred to be paleo-drainage due to the current witnessed aridity. This study aims to investigate the geomorphologic, morphometric, and stratigraphic characteristics of the paleo-drainage system and its role in recharging shallow aquifers. Morphometric analysis was accomplished using GIS and remote sensing techniques. Six vertical pit holes were dug across the area to investigate the stratigraphy and recharging capacity. The drainage system is composed of 10 closely spaced, subparallel, dendritic, elongated, and variant-sloped drainage basins with highest stream order of 5. Water flows NE from Al-Rukham ridge’s crest (60 m a.m.s.l.) downstream in Khor Al-Subiyah coastal flat. The bed rock’s hard resistant nature lowered its infiltration and recharging capacity to the shallow aquifer, whereas the coarse-grained wadi fills deposits increased infiltration capacity of the surface sediments, but the water percolation chance is limited as it eventually directed seaward by the same-directed general topography resulting in limiting potential recharge to the shallow aquifers. This is suggested to oppose the salt water intrusion and thus enhance fresh water quality.