Sources of monazite sand in southern Orissa beach placer,eastern India

This paper intends to explore whether there is an important source for monazite beach placer of the Gopalpur-Chhatrapur-Rushikulya coast, Orissa, in the adjacent Eastern Ghat Mobile Belt (EGMB). Petrographic and mineralogical studies were conducted on all the rock types constituting the EGMB exposed over a stretch extended up to ∼20 km landward from the estuary of the River Rushikulya that is believed to transport the major bulk of sand to the Gopalpur-Chhatrapur-Rushikulya beach. Heavy mineral population was concentrated using bromoform and percentages of each heavy mineral constituting the population were estimated for all the potential source rock types. Isodynamic separation and XRD techniques were deployed for precision identification of every heavy mineral present. The study identified the granitoid (or migmatite) basement rock as by far the major contributor of monazite to the Chhatrapur beach sand. The study also reveals that charnockite is an important contributor of orthopyroxene as well as garnet, although the sillimanite-garnet-quartz schist (khondalites) is also an important source for the latter. On the other hand, garnet-quartz schist and garnet-biotite-quartz schist may also contribute substantial quantity of pyroxene and garnet. The high grade metasedimentary rocks, in general, could be the major sources for rutile, while ilmenite, magnetite and zircon in the beach sand have their sources perhaps in all the varieties of rocks constituting the EGMB.     

A remote sensing based analysis of climate change in Sikkim supported by evidence from the field

The Himalayas hailed as the ‘water towers of the world' feed many perennial rivers which form the lifeline of the Indian sub-continent. Climate change induced rising global temperatures and changing rainfall patterns are currently threatening the glaciers that feed the rivers. The combination of these factors is causing water stresses to a part of the world which is usually considered water abundant. Though there are some large-scale studies done in the Himalayas, regional analysis of changing rainfall patterns and their impacts on vegetation and agriculture is lacking. Here we focus on the Indian state of Sikkim located in the Eastern Himalayas to evaluate these issues using mixed methods. We use satellite data from PERSIANN and MODIS to characterise the regional rainfall, vegetation, and surface temperature trends between 2001 and 2019. While the analysis shows overall declining rainfall trends across most land cover classes, the trends in temperature are mostly positive for the period of study, with winter Land Surface Temperature(LST) values showing the largest area with marginally significant(p0.1) positive trends. In contrast, such patterns are not observed for agriculture. However, the interviews corroborate that even agriculture is impacted, implying that the trends continue at finer spatial scales too. The lack of government support for adaptation and mitigation is also lamented placing the communities at a precarious position to continuing climate change.     

Shear Flow Dispersion Under Wave and Current

The longitudinal dispersion of solute in open channel flow with short period progressive waves is investigated. The waves induce second order drift velocity in the direction of propagation and enhance the mixing process in concurrent direction. The 1-D wave-period-averaged dispersion equation is derived and an expression for the wave-current induced longitudinal dispersion coefficient (WCLDC) is proposed based on Fischer's expression (1979) for dispersion in unidirectional flow. The result shows that the effect of waves on dispersion is mainly due to the cross-sectional variation of the drift velocity. Furthermore, to obtain a more practical expression of the WCLDC, the longitudinal dispersion coefficient due to Seo and Cheong (1998) is modified to incluee the effect of drift velocity. Laboratory experiments have been conducted to verify the proposed expression. The experimental results, together with dimensional analysis, show that the wave effect can be reflected by the ratio between the wave amplitude and wave period. A comparative study between the cases with and without waves demonstrates that the magnitude of the longitudinal dispersion coefficient is increased under the presence of waves.     

Meteoritic Impacts and Climatic Changes in Pliocene–Pleistocene Epoch

During the Pliocene–Pleistocene epoch, covering last ∼5.2 Ma of Earth’s history, altogether 34 terrestrial meteoritic impact craters are known. Most of these craters (29) have diameter ≤10 km, among which 11 craters fall in 1,000 to 100 m range, and 7 are still smaller in dimension and of recent age. The age versus impact-frequency plot shows that the meteoritic impacts during this time period occurred in discrete intervals but have a periodicity that shows the best possible coincidence with the ∼425 Ky climatic cycles observed by Fourier analysis and FFT filtering of composite high resolution benthic foraminiferal δ¹⁸O record. This observation is also supported by Monte Carlo test with 71% success where meteoritic impact(s) shows coincidence with climatic cooling within our error limit. The newly observed climatic–meteoritic cycle may be same with the ∼400 Ky Milankovitch cycle or it is a different newly understood cycle relating both the climatic variation and meteoritic impact events.     

Impact of land-use and land-cover change on groundwater quality in the Lower Shiwalik hills: a remote sensing and GIS based approach

Human activities have exerted small to large scale changes on the hydrological cycle. The current scenario regarding groundwater resources suggests that globally there is a water crisis in terms of quantity (availability) and quality. Therefore there is a great need for the assessment and monitoring of quality and quantity of groundwater resources at local level. This paper presents a case study of the lower Shiwalik hills, in Rupnagar, Punjab, India, to trace land-use and land-cover changes during the past 17 years, with an emphasis on groundwater quality and quantity. This study was performed in alluvial and hilly terrain. The results show that the quantity of groundwater increased with the help of natural and artificial recharge due to change in land-use and land-cover pattern (increased area of fallow land). The quality of groundwater deteriorated due to input of fertilizers for enhancing the short-term soil fertility. Using a Remote Sensing and GIS based approach, we show the final results in map form. In particular we highlight a potential groundwater exploration site, which could be useful for district level planning. Our research shows that the change in land-use and land-cover affects the quantity and quality of groundwater.