East A.E.,U.S. Geological Survey |
Clift P.D.,Louisiana State University |
Carter A.,University of London |
Alizai A.,Geological Survey of Pakistan |
Vanlaningham S.,Oregon State University
Journal of Sedimentary Research | Year: 2015
Sediment production and its subsequent preservation in the marine stratigraphic record offshore of large rivers are linked by complex sediment-transfer systems. To interpret the stratigraphic record it is critical to understand how environmental signals transfer from sedimentary source regions to depositional sinks, and in particular to understand the role of buffering in obscuring climatic or tectonic signals. In dryland regions, signal buffering can include sediment cycling through linked fluvial and eolian systems. We investigate sediment-routing connectivity between the Indus River and the Thar Desert, where fluvial and eolian systems exchanged sediment over large spatial scales (hundreds of kilometers). Summer monsoon winds recycle sediment from the lower Indus River and delta northeastward, i.e., downwind and upstream, into the desert. Far-field eolian recycling of Indus sediment is important enough to control sediment provenance at the downwind end of the desert substantially, although the proportion of Indus sediment of various ages varies regionally within the desert; dune sands in the northwestern Thar Desert resemble the late Holocene-Recent Indus delta, requiring short transport and reworking times. On smaller spatial scales (1-10 m) along fluvial channels in the northern Thar Desert, there is also stratigraphic evidence of fluvial and eolian sediment reworking from local rivers. In terms of sediment volume, we estimate that the Thar Desert could be a more substantial sedimentary store than all other known buffer regions in the Indus basin combined. Thus, since the mid-Holocene, when the desert expanded as the summer monsoon rainfall decreased, fluvial-eolian recycling has been an important but little recognized process buffering sediment flux to the ocean. Similar fluvial-eolian connectivity likely also affects sediment routing and signal transfer in other dryland regions globally. © 2015, SEPM (Society for Sedimentary Geology).
Firdous R.,Geological Survey of Pakistan |
Devlin J.F.,University of Kansas
Groundwater Monitoring and Remediation | Year: 2015
Diluting granular iron with sand is a common practice performed to minimize clogging and to reduce the cost of permeable reactive barrier (PRB) installations. This study used a pore-scale image analysis technique and a reanalysis of previously published data to test the hypothesis of Bi etal. (2009) that the mixing of 15% by weight sand with a commercial, platy-grained iron medium opens the pore space between grains, exposes more reactive grain surface to flowing water, and leads to a more reactive medium (i.e., promoting faster transformation rates per unit volume of medium) than 100% by weight granular iron. Four mixing ratios (100, 85, 75 and 50% iron by weight) were compared on the basis of two morphological parameters measured in section: (1) total grain area, which correlates with the total amount of iron present, and (2) grain perimeter, which is governed by both the mobile solution-available surface and the total amount of iron present. As expected, grain areas exposed in section were highest for 100% iron packings and decreased with increasing sand content. The estimated iron grain effective perimeters (i.e., accessible to mobile water) for 85% iron-by weight mixtures were similar to 100% iron and decreased in 75 and 50% iron mixtures. The section confirmed that the presence of 15% sand by weight opened up the pore structure, likely improving the mobile-water to iron contact. The analysis of kinetic column experimental data indicated that the same trend was present in the sorption capacity term in the Kinetic Iron Model (KIM) equation, providing corroborating evidence that the iron surface availability was higher in the 85% iron medium than the 100% iron medium on a per gram of iron basis. © 2016, National Ground Water Association.
Sadiq Malkani M.,Geological Survey of Pakistan
Disaster Advances | Year: 2010
Dinosaurs from Sulaiman basin of Pakistan are found just below the Cretaceous Tertiary (K-T) boundary. After K-T boundary no dinosaurs are reported from Pakistan. Hiese dinosaurs were the huge land animals at that time and were the ruler of continents but became extinct due to natural disasters. The extinction of dinosaurs at the K-T boundary represents a big disaster as well as big bioevent and geoevent. Past is past but alerts for present and future natural disaster advances and prevention especially for earthquakes and land slidings.
Clift P.D.,University of Aberdeen |
Clift P.D.,CAS South China Sea Institute of Oceanology |
Carter A.,Birkbeck College London |
Giosan L.,Woods Hole Oceanographic Institution |
And 8 more authors.
Geology | Year: 2012
The Harappan Culture, one of the oldest known urban civilizations, thrived on the northwest edge of the Thar Desert (India and Pakistan) between 3200 and 1900 BCE. Its demise has been linked to rapid weakening of the summer monsoon at this time, yet reorganization of rivers may also have played a role. We sampled subsurface channel sand bodies predating ca. 4.0 ka and used U-Pb dating of zircon sand grains to constrain their provenance through comparison with the established character of modern river sands. Samples from close to archaeological sites to the north of the desert show little affinity with the Ghaggar-Hakra, the presumed source of the channels. Instead, we see at least two groups of sediments, showing similarities both to the Beas River in the west and to the Yamuna and Sutlej Rivers in the east. The channels were active until after 4.5 ka and were covered by dunes before 1.4 ka, although loss of the Yamuna from the Indus likely occurred as early as 49 ka and no later than 10 ka. Capture of the Yamuna to the east and the Sutlej to the north rerouted water away from the area of the Harappan centers, but this change significantly predated their final collapse.
Chandio T.A.,Geological Survey of Pakistan |
Khan M.N.,University of Karachi |
Sarwar A.,Fuel Research Center
Environmental Monitoring and Assessment | Year: 2015
The fluoride level in drinking water is an important parameter and has to be controlled in order to prevent dental and skeletal fluorosis. The objective of this study is to assess fluoride content and other water quality parameters in the samples taken from open wells, tube wells, and karezes of Mastung, Mangochar, and Pringabad areas of Balochistan province. A total number of 96 drinking water samples out of 150 were found unfit for human consumption. Area-wise analysis show that the samples from 39 sites from Mastung, 12 from Mangochar, and 13 from Pringabad were found in the risk of dental fluorosis of mild to severe nature. However, 12 sampling sites from Mastung, 8 from Mangochar, and 2 from Pringabad were identified as the risks of mottling and skeletal fluorosis or other bone abnormalities. The highest concentration of F− has been observed as 14 mg L−1 in Mastung. Correlation analysis show that fluoride solubility in drinking water is pH dependent; and the salts of Ca2+, Na+, K+, Cl−, and SO42− contribute to attain the favorable pH for dissolution of fluoride compounds in drinking water. Principal component analysis shows that the geochemical composition of the rocks is only responsible for groundwater contamination. On the basis of the results, defloridation of the identified sampling sites and continuous monitoring of drinking water at regular basis is recommended at government level to avoid further fluorosis risks. © 2015, Springer International Publishing Switzerland.