National Centre for Earth Science Studies

India is one of the oldest maritime nations in the world, and the overseas contacts date back to the third millennium BCE. Besides several archaeological vestiges, numerous stone anchors of various types have been documented during maritime archaeological explorations along the Indian littoral. During a recent maritime archaeological exploration, a broken Indo-Arabian stone anchor, of the Medieval period, was discovered along the Manikapatna coast of Odisha, Indian eastern littoral. In an attempt to determine the provenance of the anchor, we carried out a detailed petrographic, geochemical (major/trace elements) and Sr-Nd isotopic investigation. The results of our study reveal that the stone of the anchor had been cut out of a geologically young, vesicular, alkali basalt lava flow. Source fingerprinting done using petrographic, geochemical and isotopic data, suggests that contrary to the general perception, the anchor rock did not come from any local rock formations. All data point to the most likely scenario that it was sourced from one of the Deccan Traps lava flows of Palitana in the Saurashtra region of Gujarat, western India. This confirms the Medieval maritime trading between western and eastern Indian states.

Bibliographic Info: Tripati, S., Jyotiranjan S. Ray., Behera, R. P., Prakash Babu., Mahala, M. K., Murali Kocherla., Vijay Khedekar. (2022). Geochemical provenance of an Indo-Arabian stone anchor from Manikapatna highlights the medieval maritime trade of India. Scientific Reports, 12(1), 1-14. 
https://doi.org/10.1038/s41598-022-17910-9.

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The temperature of homogenization (Th) obtained through microthermometric analysis of the fluid inclusions reveals the minimum entrapment temperature to which the sedimentary rock formations have been heated to. Coeval-aqueous inclusions associated with HCFIs show Th within the oil window range 60-140 °C, indicating a temperature favourable for oil generation in Kerala - Konkan basin. The secondary data of Rock-Eval pyrolysis analyses were used to determine the source rock maturity of two wells i.e., RV-1 well from Mumbai offshore basin and KKD-1A well from Kerala - Konkan basin. Source rock parameters indicates that source rocks of RV1 well of Mumbai offshore are mature and that of KK-D-1A wells of Kerala-Konkan basin are immature. Total Organic Carbon (TOC) content present in different depths of RV-1 well is indicating desirable organic matter content of >1 wt.% (maximum TOC of 39 wt.% in the Palaeocene - Eocene sediments of Panna formation). On the other hand, TOC of organic matter present in the source rocks of Kasaragod formation in the KK-D-1A well shows TOC <1 wt.% only, indicating that the Palaeocene - Eocene sediments of Kasaragod formation is having poor source rock characteristics, due to which the generation of hydrocarbon might not have occurred even if it is entered in the oil window (60-140 °C).

Bibliographic Info: Silpa Thankan, Nandakumar, V., Shivapriya, S.. (2023). Hydrocarbon fluid inclusions and source rock parameters: A comparison from two dry wells in the western offshore, India.https://doi.org/10.1016/j.gsf.2022.101464.

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The rivers in the southern Western Ghats play an important role on sustaining the richness and diversity of the biotic environment in the mountainous catchments. However, human interventions in the last 4-5 decades have imposed immense stress on this ecologically sensitive system. The environmental problems are worse in the downstream reaches of the rivers that host the major industrial and urban centres. In a recent study, the scientists of Hydrology Group revealed that lockdown during COVID pandemic was an eye-opener to the extent of river pollution and also point to the imminent need for long-term plans to recoup the natural cleansing ability of the river systems. The results of the water quality study in the industrialised and urbanised regions of the Periyar river revealed that over 90 % of the river water samples, which were examined during the lockdown period, showed excellent-good water quality, but the figure declined below 50 % during post lock down period due to excessive flux of pollutants from industrial and urban centres. The results of the study underscore the urgent need for establishing high-performance Sewage Systems Treatment (STPs) to pre-treat waste waters to acceptable levels before discharging in to the riverine environments.

Bibliographic Info: Aditya, S. K., Krishnakumar, A., Anoop Krishnan, K. (2023). Influence of COVID-19 lockdown on river water quality and assessment of environmental health in an industrialized belt of southern Western Ghats, India. Environmental Science and Pollution Research, Vol. 30 (28), pp. 72284-72307.https://doi.org/10.1007/s11356-023-27397-0.

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The extreme rainfall events observed at a High- Altitude Cloud Physics Observatory (HACPO) site in Rajamallay, Munnar (10° 9’ 19.94” N, 77° 1’ 6.65” E, 1820 m above MSL) over the southern Western Ghats (India) during the floods in 2018 and 2019 monsoon periods (16th August 2018 and on 8th August 2019) have been investigated. The drop size distribution (DSD) spectra during the 2018 event are characterized by a large number of small to medium-sized drops resulting in maximum reflectivity of 48 dBZ with mass-weighted mean diameter (Dm) value of 1.2 mm. At the same time, the 2019 event is characterized by larger drops and resulted in high reflectivity of 53 dBZ and Dm value shifted to 1.4 mm. The consistent increment of Dm with variation in number concentration of drops during the intensive rain hours on 8th August 2019 shows a mixed- phase microphysical process that can invigorate the production of convective rainfall from deep cloud bands (217 K of cloud top temperature) with enhanced rain water content (22 gm-3 ). The parameters of scaled raindrop size distributions corresponding to higher rain rates (>50mmhr-1 ) suggest that the microphysical process that control the variations in DSD is strongly number controlled during these extreme rainfall events. The DSDs are evolved from a consistent, widespread rainfall supported by anomalous moisture advection from the Arabian Sea in 2018 monsoon period. The moisture convergence occurred on the elevated terrains leads to an intense spell of rainfall in two consecutive hours satisfies the occurrence of mini-cloud burst events on 8th August 2019 causing flash flood in the region.

Bibliographic Info: Sumesh, R. K., Resmi, E. A., Unnikrishnan, C. K., Dharmadas Jash, Padmalal, D. (2022). The extreme precipitation events of August 2018 and 2019 over southern Western Ghats, India A microphysical analysis using in-situ measurements. Atmospheric Research, Vol. 277, Art. 106322. https://doi.org/10.1016/j.atmosres.2022.106322.

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Assessment of monsoon moisture sources and their variability by secondary environmental controls was carried out in South India using stable isotopic composition of oxygen and hydrogen in rainwater. The rainwater isotopic signature in southwest India reflected dual monsoon sources with moisture from Arabian Sea and equatorial Indian Ocean during summer monsoon season, and a few depressions and cyclones generated over the Bay of Bengal formed the winter monsoon sources. The predominant summer monsoon rainwater along the eastern Arabian Sea coast reflected rainfall from first condensate while the marine moisture signatures were altered by the evapotranspiration process in inland regions indicating continental moisture recycling effect. The calculated high deuterium excess values (d-excess = 10-18‰) for observed rainwater also suggested higher influence of local precipitation effect in humid tropical river basins of the Western Ghats which usually exhibited annual average relative humidity ~ 85 % and temperature ~ 25°C. The time and space variability of regional moisture circulation in controlling atmospheric water balance was deduced in this study. The findings of this study revealed microclimate manifestation in the Western Ghats region similar to other cloud forest ecosystems like in South America (for e.g., Amazon basin), Hawaii, Eastern and Central Africa, Indonesia, etc.

Bibliographic Info: Tripti Muguli., Lambs, L., Gurumurthy, G. P., Moussa, I., Balakrishna, K (2022). Isotopic fingerprinting of dual monsoon moisture sources, evapotranspiration process and microclimate manifestation over the tropical rainforest region, western part of the Western Ghats, India. Journal of Hydrology, 612, 128239. https://doi.org/10.1016/j.jhydrol.2022.128239.

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