An appraisal of the piedmont fan topography between Tista and Jaldhaka rivers,West Bengal

Aerial photographs and LANDSAT images have been used in conjunction with existing topographical and geological information to prepare a land unit map of the Piedmont plain of the Himalaya between the Tista and Jaldhaka Rivers, in parts of Darjeeling Jaiguri districts, West Bengal. Such study was carried out to analyse the Piedmont Fan deposits, fluvial processes, effect of Quaternary tectonics on the morphogenesis of terraces (land units), morphodynamic processes operating on the units, and present land utilisation pattern. Geomorphologically, the area encompasses a multi-staged, fluviogenetic compound land units of five distinct Fan-cut and fill terraces originated due to an intensive interaction of endogenic (related to Himalayan upheaval), masogenic (relared to reactivation of lineaments) and exogenic (surfacial morphodynamic processes including mass wasting) factors during the Quaternary period. Widespread change of Paleo-environmental conditions along with tectonic disposition during the Quaternary period had the major influence on the Piedmont morphogenesis. The area probably underwent at least five phases of tectonic rejuvenation in a cycle of anagenetic revival of this land system. The present day configuration of Fan-terrace assemblage and their content is, therefore, representating a metastable form-equilibrium condition in an open channel system.     

Sedimentary structures displayed by the ultramafic rocks of Nausahi,Keonjhar District,Orissa, India

Gravity-controlled and other sedimentary structures exhibited by the ultramafic rocks of Nausahi, Keonjhar District, Orissa, India, are described and their significance briefly discussed. Mineral-graded and size-graded layering, slump structure and cusp textures formed by the influence of gravity, indicate that the ultramafic rocks under study have not been overturned and that the original depositional floor had a gentle north-easterly slope. The magmatic currents were locally strong enough to give rise to some characteristic structures like small-scale angular discordance, branching of chromite lamina, inclusion of one rock type in another, etc. There are also some structures resembling ripple mark and load cast. The pyroxenite dykes and veins were intruded predominantly in the solid state into the dunite-chromitite associations.     

On the thermal and redox history of the Yamato diogenite Y-74013

The Yamato diogenite, Y-74013, shows a high degree of textural equilibrium with the apparent crystallization sequence: troilite and metal → orthopyroxene → plagioclase. The position of the large chromite crystals in this sequence is unclear. Except chromite, all other minerals have composition similar to common orthopyroxene achondrites. The chromite is more magnesian than in common diogenites, strongly zoned and, on the whole, intermediate in composition between chromites of diogenites and pallasites. Texture, mineral composition data and an equilibrium thermodynamic analysis of the mineral association strongly indicate that the chromite crystallized earlier than the silicates at a much higher temperature (possibly above 1100°C) and rapidly grew in a medium which was progressively enriched in Mg, Al and Ti. But the chromite failed to reach chemical equilibrium, even at its outermost rim, with the orthopyroxene. The calculated equilibrium log fO₂ of the Yamato diogenite, ?20·21 to ?11·08 for temperatures between 880°C and 1500°C is well within the normal oxygen fugacity range of pyroxene achondrites.     

Biopolymer-biocement composite treatment for stabilisation of soil against both current and wave erosion

Acta Geotechnica - Increased frequency of extreme weather events has made the conservation of riverbanks and coastlines a global concern. Soil stabilisation via microbially induced calcite...     

Discovering Axion-Like Particles Using Cosmic Microwave Background as the Backlight

Astronomy Reports - Particle physicists and cosmologists have sought axion-like particles (ALPs) ever since they were postulated in quantum chromodynamics and string theory. We propose probing the...