National Centre for Earth Science Studies

A compilation of available detrital zircon age data and their Hf isotopic compositions from the Indian subcontinent revealed the following about the crustal evolution in India. (1) The four significant/major peaks in the age spectrum at 2700-2400, 1900-1600, 1200-850, and 550- 450 Ma can be correlated with the major supercontinent cycles. (2) The peaks at <100 Ma and 3400-3200 Ma likely represent Himalayan orogeny and enhanced erosion and exhumation of Archean sources, respectively. (3) The zircon εHf(t) variations suggest that the Precambrian crust was the major source of young continental crusts. The positive zircon εHf(t) values from ca. 3600 to 3200 Ma age groups suggest a greater degree of mantle melting or a shift from stagnant lid to mobile/ intermittent lid tectonic environment. The highly negative zircon εHf (t) values after 3200 Ma signify a greater degree of recycling and reworking of the older continental crust probably implying the onset of plate tectonic processes; (4) The CWT wavelet analysis on detrital zircons from the Indian and global databases reveals a prominent cyclicity of ~800 Myr and ~350 Myr plausibly representing the supercontinent cycle and its half cycle. However, an incongruence in power between the global and Indian εHf(t) could be due to the local subcontinental geologic processes during the Paleo to Mesoarchean

Bibliographic Info: Kumar Batuk Joshi., Upasana S. Banerji., Dubey, C. P., Oliveira, E. P. (2022). Detrital Zircons in Crustal Evolution A Perspective from the Indian Subcontinent. Lithosphere, 2022(Special8),d3099822. https://doi.org/10.2113/2022/3099822.

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The Kaladgi Basin is one of the several Proterozoic sedimentary basins of India. This basin has a binary evolutionary history with an angular unconformity separating the older deformed and younger undeformed rock sequences of the Kaladgi Supergroup, named the Bagalkot and Badami Groups, respectively. The Bagalkot Group is believed to be of late Paleoproterozoic to Mesoproterozoic in age. However, the timings of deposition of the Badami Group and the closure of the basin have remained speculative. Our 206Pb-207Pb dating of the youngest unit of the Supergroup, the Konkankoppa Limestone yielded a depositional age of 604 ± 25 Ma (MSWD=1.2). This age, considered together with the lowest 87Sr/86Sr ratio of 0.70781 observed in the formation, extends the active sedimentation of the Badami Group well into the Ediacaran Period. These data confirm the existence of a long duration depositional hiatus, of >500 million years, between the Bagalkot and the Badami Groups. Results of this study also refutes the claim that the sedimentation in most of the Proterozoic basins of peninsular India ended by 1000 Ma.

Bibliographic Info: Bivin G. George, Jyotiranjan S. Ray, Pillai, S. P., Mahala, M. K., Kumar, S., Kale, V. S. (2023). C-Sr-Pb isotope systematics of the carbonate sequences of Kaladgi Supergroup, India: Implications for basin evolution and correlation with Proterozoic global events. Precambrian Research, Vol. 388, Art. 107014.
https://doi.org/10.1016/j.precamres.2023.107014.

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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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