Research Updates

vdm Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods. Here, we present the first robust experimental data from the largest Cretaceous flood basalt province on Earth, the ~65–66 Ma Deccan basalt within a thick (1250 m) unbiased stratigraphic section down to the basement, recovered from a drill hole of the Koyna Deep Scientific Drilling Project in the Western Ghats, India. Critical analysis of the result along with similar results of the Cretaceous age find that (i) the dipole moment during the end Cretaceous Deccan eruption is the lowest in whole of Cretaceous (ii) dipole moment at the onset/termination of the Cretaceous Normal Superchron is apparently lower relative to that in mid-superchron, however, such differences cannot be deciphered in shorter polarities probably because of insufficient time to develop recognizable variations (iii) inverse relation between dipole moment and reversal rate is lacking and (iv) a cause and effect relation between core-mantle boundary heat flux and low dipole moment that appears to be the principle governing factor in forming the Large Igneous Provinces on the surface of earth.

Bibliographic Info: Radhakrishna, T., Asanulla R. Mohamed, Venkateshwarlu, M., Soumya, G. S. [2020]. Low geomagnetic field strength during End-Cretaceous Deccan volcanism and whole mantle convection. Scientific Reports, Vol. 10 (1), Art. 10743. https://doi.org/10.1038/s41598-020-67245-6

 

conceptual

The quiet time characteristics of equatorial electrojet (EEJ), counter electrojet (CEJ), and solar quiet (Sq) day geomagnetic field over two decades (1980–2002) are established using Principal component analysis (PCA) from equatorial (Ettaiyapuram) and off‐equatorial (Hyderabad) Magnetic Observatories, India, over sunspot cycles 21–23. The patterns of normal field shows that the diurnal amplitudes were strong during equinox compared to other seasons. Varying contributions of abnormal field in different Lloyd's seasons were evident in different phases of sunspot cycle. The diurnal amplitudes have reduced from the 21st to the 23rd sunspot maxima following the trend of weakening of sunspot cycle. Analysis of seasonal means shows evening CEJs were more pronounced when compared to morning and afternoon in different phases of sunspot cycle. The abnormal field variations have a strong correlation with the occurrence of afternoon CEJs during solar minima; a correlation of seasonal occurrences of CEJs with phases of sunspot cycles is revealed.

Bibliographic Info: Chandrasekhar, N. P., Arka Roy [2020]. Imprints of sunspot cycles on normal and abnormal geomagnetic fields: Case study from equatorial and low‐latitude sites of India. Journal of Geophysical Research: Space Physics, Vol. 125 (12), Art. e2020JA028464. https://doi.org/10.1029/2020JA028464

 

 

PatentA patent was granted for an invention entitled ‘A multi-spectral diffuse reflectance imaging system for diagnosis of oral cavity cancer’
Patentee Info: Dr. J. L. Jayanthi, Dr. Subhash Narayanan
National Centre for Earth Science Studies.
Intellectual Property India, Patent No. 347763 dated 25/09/2020.

 

conceptualThe west coast of India is one of the important geothermal provinces that hosts many thermal springs of varying discharge characteristics. A total of twenty thermal springs have been reported in this region falling into two different suites of geological formations. Two low temperature geothermal springs located in the south Konkan region were studied with the objectives (1) to understand the geochemical evolution, (2) to identify the recharge source and (3) to propose a reservoir temperature. The hydrogeological and geochemical investigations were carried out on two geothermal springs, viz. Bandaru and Irde, both located in the Dakshina Kannada district of the Karnataka state, India. In this region, low-temperature geothermal activity has been reported in the form of the evolution of warm water from thermal spring systems with a notable presence of faults/lineaments in the geological formation. These faults enable the upward flow of geothermally heated water. The hydrochemistry of water samples was analyzed to determine the dominant hydrogeochemical processes in the region. These thermal springs are categorised as Na-HCO3 type facies. The thermal water is of a moderately alkaline nature like other geothermal springs of the west coast of India. Based on the results for major and trace element concentrations it was found that the hydrochemical process was mainly controlled by the dissolution of silicate minerals with a marginal influence from anthropogenic activity. Evaluation of δD and δ18O stable isotope data suggested that the thermal springs and adjacent surface and groundwater were of meteoric origin. Reservoir temperature was estimated with Na-K-Ca, K2/Mg, quartz and chalcedony geothermometers. The results suggest that the reservoir under consideration is a low enthalpy reservoir with temperatures ranging between 55 and 86 °C.

Bibliographic Info: Prasenjit Das, Maya, K., Padmalal, D. [2020]. Hydrochemistry, geothermometry and origin of the low temperature thermal springs of South Konkan region, India. Geothermics, Vol. 90, Art. 101997. https://doi.org/10.1016/j.geothermics.2020.101997

Es The increase in demand of building stones and construction-grade sand has resulted in aggressive hard rock quarrying in many parts of the world. The problems are to be evaluated in detail for the judicious use of resources on the one hand and ensuring health of the ecosystems on the other. The present study aims to evaluate the impact of hard rock quarrying on one of the important twin - river basins in SW India, the Netravati–Gurpur river basin, which hosts the fast developing urban centre, the Mangalore city. A total of 64 hard rock quarries are located in the basin which together extracts about 6.75 million t y−1 of rocks/rock products for different purposes. An assessment of the impacts of quarrying using the rapid impact assessment matrix (RIAM) reveals marginal, short-term positive impacts in economic-operational components but major negative impacts on all the other environmental components. The study indicates that the present intensity of quarrying is unsustainable with a sustainability index of − 0.25. Therefore, hard rock quarrying in the study area is to be strictly regulated for bringing down the river basin degradation to the barest minimum level and maximizing the ecosystem benefits to its full potential.

Bibliographic Info: Vandana, M., Shiekha E. John, Maya, K., Syam Sunny, Padmalal, D. [2020]. Environmental impact assessment (EIA) of hard rock quarrying in a tropical river basin - study from the SW India. Environmental Monitoring and Assessment, Vol. 192 (9), Art. 580. https://doi.org/10.1007/s10661-020-08485-x