Journal of The Indian Association of Sedimentologists (peer reviewed)

Editorial

G M Bhat — Tue, 31 Dec 2024 00:00:00 +0000

The UN Climate Change Conference (COP29) concluded on 24 November 2024 with a new finance goal to help countries to protect their people and economies against climate disasters, and share in the vast benefits of the clean energy boom. With a central focus on climate finance, COP29 brought together nearly 200 countries in Baku (Azerbaijan) and reached an agreement to provide 300 billion USD finance to developing countries annually by 2035 and secure efforts of all actors to work together to scale up finance to developing countries, from public and private sources, to the amount of USD 1.3 trillion per year by 2035. "This new finance goal is an insurance policy for humanity, amid worsening climate impacts hitting every country,” said Simon Stiell, Executive Secretary of UN Climate Change. Stiell also acknowledged, “The agreement reached in Baku did not meet all Parties' expectations, and substantially more work is still needed next year on several crucial issues”. World leaders at COP29 were joined by civil society, sub-nationals, business, Indigenous Peoples, youth, philanthropy, and international organizations. More than 55,000 people attended COP29 to share ideas, solutions, and build partnerships and coalitions. COP29 marked a significant milestone as dedicated spaces were created to ensure the meaningful participation of children within the Youth-led Climate Forum for the first time. Four children, including the youngest (just 10 year old), took on roles as moderators and speakers, engaging directly with Parties and observer organizations. Their participation highlighted the importance of inclusivity and intergenerational collaboration in driving climate action.

Provenance of minerals in the Assi river sediments, Varanasi, Uttar Pradesh, India

Tue, 31 Dec 2024 00:00:00 +0000

Grain size analysis and mineralogical characterization are important sedimentological tools to interpret the depositional environment, source, hydrodynamic conditions, and mode of transport of river sediments. Clays derived from chemical weathering are an important group of minerals found in various sedimentary environments such as rivers, estuaries, and ocean. In the present study, mineralogy of Assi river sediments was investigated with the help of Fourier Transform Infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM). Results revealed that the sediments are dominated by sand and mud. Further, the sediments were found to be abundant in quartz with subordinate amount of feldspars, kaolinite, illite, chlorite, and montmorillonite. Abundance of these minerals suggests that the Himalayan and Vindhyan sedimentary rocks are the primary source for the Assi river sediments.

Lithofacies and Granulometric Analysis of Middle Siwalik Sandstones of Jammu, NW Himalaya, India

S K Pandita, Sumit Johar, Shifali Chib, Yudhbir Singh, G M Bhat, S S Kotwal — Tue, 31 Dec 2024 00:00:00 +0000

In the Northwest Himalaya, the Siwalik Group of rocks are exposed in the Suruin-Mastgarh anticlinal folded succession and has been classified into Lower, Middle and Upper subgroups. The Middle Siwalik Subgroup is exposed at various locations in the Jammu region and is primarily made up of multistoried sandstones embedded with thin beds of mudstone. In the present study, these rocks have been studied to understand the depositional history using the sediment size of sandstones and the lithofacies in addition to the paleocurrent analysis. The multistoried nature of the sandstone and the scour fills observed in these rocks imply that there were frequent and periodic strong stream encounters at the depositional site where saltation was the dominant process of transportation of sedimentsThe data obtained on grain size, lithofacies, cross beddings, and the type of contacts between different lithofacies suggest that the southerly flowing braided river system underwent multiple episodes of avulsion and abandonment of the channel system during the deposition of the Middle Siwalik subgroup in Jammu region.

Geochemistry of sandstones from the Imphal Valley, Indo-Myanmar Ranges

Salam Ranjeeta Devi — Tue, 31 Dec 2024 00:00:00 +0000

Spheroidal weathered siliciclastic rocks of the Imphal Valley, Indo-Myanmar Ranges were studied to determine paleoclimate, paleoweathering and mineral alteration based on the geochemical and mineralogical compositions. The Chemical Index of Alteration (CIA) suggests low-intermediate chemical weathering. Plagioclase Index of Alteration (PIA) value indicates incipient plagioclase alteration. Mineralogical Index of Alteration (MIA) reveals incipient to intermediate mineralogical alteration and the A-CN-K ternary plot of the studied samples suggests a low rate of alteration. The results suggest semi-arid climate, which ranges from warm-arid to warm cool conditions. Geochemistry and mineralogy indicate felsic, mafic and ultramafic compositions for the siliciclastic rocks.

Micromorphology of basalt alterite and its implications on the geological processes during quiescence period of the Deccan volcanism, Kharghar hill, Maharashtra, India

Anshul Dhiman, Seema Singh, Soumyajit Mukherjee — Tue, 31 Dec 2024 00:00:00 +0000

Palaeoweathering unearths hidden mysteries of the previously weathered (paleo) surfaces. Researchers have shown that each mineral weathers/alters in a particular manner and is process-specific. Micromorphology is the most reliable and well-established technique to identify process-specific features imparted in an alterite under a given set of conditions. The Indian Deccan traps form one of the world’s largest flood basalt volcanic provinces and has numerous exposures. Notwithstanding, systematic micromorphological studies of Deccan flood basalts are lacking compared to such flood basalts of global occurrences. The episodic nature of Deccan volcanism provided subsequent phases of interaction with the Earth’s surface processes, thereby making the basalt alterites an ideal repository of surficial conditions and subsequent duration. Deccan basalt alterite exposed in the Kharghar hill of Mumbai (Maharashtra) has been selected for detailed micromorphology. Micromorphological results from the top to bottom of >70 cm thick, buried basalt alterite show changes in specific pattern of primary mineral alteration, formation of secondary minerals, development and patterns of secondary porosity. For example, the top of studied alterite (i.e. top 30 cm) has irregular, speckled and patchy patterns of mineral alteration, intramineral secondary pores, dominance of secondary products and only isolated alteromorphs that too with large elongate patches. Whereas towards the bottom (i.e. below 30 cm), the alterite shows planar patterns of mineral alteration, which is preceded at places by a linear/speckled pattern and most distinct is the dominance of intermineral pore system connected with transmineral fractures. Therefore, the basalt alterite can be subdivided from top to bottom into two distinct layers namely, alloterite and isalterite. This distinction significantly indicates a change in process with time as well as duration of basalt interaction with then prevailing surficial conditions. Thus, it can be concluded that alteroplasmation was progressively and gradually replaced with pedoplasmation resulting in dominance of supergene processes over hypogene processes.

Morphometric evaluation of diverse ripple structures in the Alwar Group at Jamwa Ramgarh in NE Rajasthan, North Delhi Fold Belt, NW India

Dr Asha Saxena, Prof. M. K. Pandit, Nirmal Kant Verma — Tue, 31 Dec 2024 00:00:00 +0000

In this study we describe a complex set of well-preserved ripple structures from the Alwar Group quartzites (quartz arenite) of Mesoproterozoic Delhi Supergroup in NW India. Exposed in a road section near Jamwa Ramarh (to the east of Jaipur city), a large abundance and diversity in ripple shape, size, wave amplitude and mode of occurrence is unique for a small geographic area. The studied ripples are predominantly symmetric in shape, showing bifurcations, sinuous types, pointed crest with rounded trough, etc. Occasional current and criss-cross, and mega ripples are also present. Their symmetric shape suggests a wave dominant environment. The Vertical Form Index (VFI) values or Ripple Index values below 15 further rule out any possibility of a wind origin for them. The criss-cross and interference ripples point toward the presence of a high energy river system in the vicinity. The statistical analysis of ripple morphological parameters indicates deposition of quartz arenite under shallow water conditions (< 3 m depth). Based on various morphometric analyses, we infer continental shelf with variable depth for the development of these wave ripples. Based on the crest-line criterion, the inferred paleocurrent direction was from the NW.

Tertiary Coal Deposits from the North-eastern Region of India – A review

Manabendra Nath — Tue, 31 Dec 2024 00:00:00 +0000

This review paper aims to provide a comprehensive account of the Tertiary coal resources of north-eastern region of India. The coal belt of North-East India developed in two different geo-tectonic settings – one is the foreland basin (Assam, Arunachal Pradesh, Nagaland Oligocene coals) and the other platform areas (Meghalayan Eocene coals). The rank of eastern Himalayan coals varies from sub-bituminous to high volatile bituminous C. The carbon content of Oligocene coal is much higher and show caking characteristics. The coals of this part of India have low ash (<8%), low moisture (<5%), high volatile matter (>40%), high sulphur (>3%), high hydrogen content (>4%), low nitrogen (<1%) and oxygen (<12%). Petrographically they are rich in vitrinite, moderate Liptinite and low inertinite. High concentrations of trace elements (like Cu, Cr and Ni) and sulphur content indicate marine influence in the depositional basin. In the north-eastern coals the dominance of typical Tertiary angiosphermic floral assemblage is well indicated by the occurrence of single, double and triple celled telutospores.