Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections

1IntroductionThe Late Mesozoic sequences of Afghanistan are important in understanding the geodynamic evolu-tion of the northwestern part of South Asia, in par-ticular the transgressive and regressive history of the northwestern part of the Tethys connecting Iran to the west and the northern Indian Subcontinent to the east. Jurassic to Upper Cretaceous sedimentary seque-nces were initially studied by Griesbach (1885 ~1887) and Hayden (1880~1901) through several traverses in northern an…     

Experimental study on loss factor for corrugated plates by bandwidth method

The material loss factor for technically orthotropic plates was measured by half-power bandwidth method. Rectangular and trapezoidal corrugated plates of steel were considered. A simple isotropic steel plate was also considered for comparison of the results. The concept of single degree of freedom system was adopted. The tests were undertaken at very low frequency range (0–100) Hz. The plate models were suspended freely with two wires to minimize or prevent excessive extraneous energy dissipation. Out of plane point force, random in nature was applied to the top middle of the plates and the responses were measured from the middle point of the plates by FFT analyzer using miniature small mass accelerometer as sensor. The aim of these tests is to investigate the effects of bending rigidity and mode orders over material loss factor. The values of estimated modal damping loss factors are compared and tabulated for the plates models considered. Natural frequencies of some of the initial modes of the plates are also presented.It is observed that the higher the value of bending rigidity of the plates, the larger the values of loss factor of it. There was a significant increase in value of loss factor in corrugated plates to that of the isotropic plate.     

Metamorphic and deformational imprint of Cambrian–Lower Ordovician rifting in the Ossa-Morena Zone (Iberian Massif, Spain)

The high-temperature metamorphism recorded in the Valuengo and Monesterio areas constitutes a rare occurrence in the Ossa-Morena Zone of Southwest Iberia, where low-grade metamorphism dominates. The metamorphism of the Valuengo area has been previously considered either Cadomian or Variscan in age, whereas that of Monesterio has been interpreted as a Cadomian imprint. However, these areas share important metamorphic and structural features that point towards a common tectonometamorphic evolution. The metamorphism of the Valuengo and Monesterio areas affects Late Proterozoic and Early Cambrian rocks, and is syn-kinematic with a top-to-the-north mylonitic foliation, which was subsequently deformed by early Variscan folds and thrusts. The U–Pb zircon age (480±7 Ma) we have obtained for an undeformed granite of the Valuengo area is consistent with our geological observations constraining the age of the metamorphism. We propose that this high-temperature metamorphic imprint along a NW–SE ductile extensional shear zone is related to the crustal extension that occurred in the Ossa-Morena Zone during the Cambro-Ordovician rifting. In the same way, the tectonothermal effect of the preorogenic rifting stage may have been wrongly attributed to orogenic processes in other regions as well as in this one.     

Effect of salinity on chlorophyll concentration, leaf area, yield and yield components of rice genotypes grown under saline environment

Salt tolerance in eighteen advanced rice genotypes was studied under an artificially salinized (EC=8.5 dSm^?1) soil conditions after 90 days of transplanting. The results showed that the yield per plant, chlorophyll concentrations, fertility percentage, and number of productive tillers, panicle length and number of primary braches per panicle of all the genotypes were reduced by salinity. However, genotypes viz. Jhona-349 x Basmati-370, NR-1, DM-59418, DM-63275, DM-64198 and DM-38-88 showed better salinity tolerance than others.     

Potassium induced salinity tolerance in wheat (Triticum aestivum L.)

Water culture experiments were conducted to study the response of ten wheat genotypes to external K application (10 mmol KCI dm^?3) at seedling stage under saline condition (0 and 100 mmol NaCl dm^?3). The data showed that there was an increase in the shoot and root length with the application of external K. The increase was more pronounced under control than under saline conditions. The better performing genotypes under two treatments were Bhitai, NIAB-41, NIAB-I076 and Khirman. The enhanced growth of these genotypes under saline condition might be due to the quick response to external K application, resulting in high K/Na ratio. The results indicated that the genotypes, which have the ability of enhanced K/Na discrimination, might perform better under saline conditions when sufficient potassium is applied in the rooting medium.     

Assessment of pollution sources in the southeastern of the Riyadh and its impact on the population/Saudi Arabia

The rapid growth of Riyadh—capital of Saudi Arabia—is pushing the area to more pollution and incentive for reorganization. The aim of this research is to assess air pollutants in southeast of Riyadh and detect opinion of the population about their environment. The assessment was done by analyzing 405 questionnaires, evaluating thermal band of Landsat 8, and spatial analyzing of particular matter and chemicals in 19 air samples by geostatistical tool in the ArcMap. Most of the inhabitants stated that they are suffering from bad odor, sewage leakage, and dust mainly from a cement factory. The thermal band of Landsat clarified the location of the pollution sources mainly the 1st industrial city, Yammama Cement Factory, and power plant in Farouq area. The ordinary kriging maps showed that the highest concentration of PM₁₀ (>403 μg/m³) lied to the northern and western side of the study area and caused a health issue to most inhabitants.     

Late Cretaceous–Early Paleogene tectonic events at Farafra-Abu Minqar Stretch,Western Desert,Egypt: results from calcareous plankton

This work depends on integrated high-resolution calcareous plankton nannofossil and foraminiferal biostratigraphic analyses for three Upper Cretaceous-Lower Paleogene successions at Farafra-Abu Minqar area, Western Desert, Egypt. These sections are distributed in a north-south geologic profile as follows: El Aqabat, North Gunna, and Abu Minqar. Lithostratigraphically, four formations are recorded in the study area, namely, Khoman (at base), Dakhla, Tarawan, and Esna (at top). In the north at El Aqabat section, Khoman Formation (carbonate facies) is only represented which changes partially toward the south to Dakhla Formation (siliciclastic facies). In the extreme south at Abu Minqar section, it changes completely into siliciclastic facies of Dakhla Formation. Biostratigraphically, seven calcareous nannofossil and eleven planktonic foraminiferal zones represent the Late Cretaceous-Early Paleogene are identified. Based on the occurrence or missing of these zones accompanied with the field criteria resulted in detecting four tectonic events. These tectonic events took place at the Cretaceous/Paleogene (K/Pg), the Danian/Selandian (D/S), the Selandian/Thanetian (S/T), and the Paleocene/Eocene (P/E) boundaries. These tectonic events are related to the impact of the Syrian Arc System. Four sequence boundaries (SB1, SB2, SB3, and SB4) are defined in the Late Cretaceous-Early Paleogene sequence in the Farafra-Abu Minqar area.     

Gravity field and structures of the Rajmahal Hills: Example of the Paleo-Mesozoic continental margin in eastern India

A narrow strip of Gondwana basins separates the Rajmahal traps from the peninsular shield in eastern India. This part of the shield margin is associated with a conspicuous gravity high of 100 km wavelength and 48 mGal amplitude over an area of 25,000 km². Second order residual anomalies due to Gondwana sediments and traps are superposed on this wider gravity high. Gravity interpretation, partly constrained by seismic data, suggests that the wider high is caused by a denser metamorphic layer (amphibolite and granulite) up to 3.5 km thick. The metamorphic layer also extends below the eastern Rajmahal hills where the Gondwanas, traps and younger sediments have covered it. The Gondwanas are downfaulted against the shield edge and are preserved over an irregular basin floor whose deepest part underlies the eastern flank of the Rajmahal hills adjacent to the Bengal basin. It is inferred that the Gondwanas were deposited over a rifted and highly faulted shield margin that was intruded by the Rajmahal traps nearly 100 m.y. ago. High-grade metamorphism along the shield edge presumably preceded the continental rifting, perhaps occurring in the Precambrian as a part of the Eastern Ghats orogeny, along the east coast of India.