Journal of The Indian Association of Sedimentologists (peer reviewed)

Editorial

Ganapati Narayan Nayak — 2026-06-30

The Bay of Bengal is a large but relatively shallow embayment of the northeastern Indian Ocean. It receives a significant amount of freshwater and sediment, approximately 2000 million tonnes annually, from the Himalayan and the Indian peninsular rivers during the North East (NE) and the South West (SW) monsoons, respectively. The sediment flux to the bay is among the highest globally due to its size, location, and the catastrophic deposition of sediments. Long paleo-synoptic reconstructions and paleomonsoon interpretations from sediment cores in the Bay of Bengal are limited. This is largely because the enormous sediment load that enters the Bay through river discharge occurs under high-energy conditions, making it challenging to retrieve turbidity-free and undisturbed sediment cores. However, some recent reports (Ponton et al., 2012; Tripathy et al., 2014) have documented variations in paleoclimate and geochemical cycles from the Last Glacial Maximum to the late Holocene period in the Bay of Bengal. Sedimentological and geochronological studies conducted on the eastern Bengal shelf studied by Kuehl et al. (1989) revealed that the highest sediment accumulation from the Ganges-Brahmaputra river system occurs near the head of the Swatch of No Ground, which is located west of the present river mouths of Ganges-Brahmaputra. Additionally, Kolla and Rao (1990) analyzed sediment sources from the Bay of Bengal and reported high quartz and low calcium carbonate percentages adjacent to the Indian subcontinent, likely due to a substantial influx of terrigenous clastics. Furthermore, investigations on the mineralogy and heavy minerals in sands suggest that sediments of the western Bengal Fan, characterized by high levels of smectite, sillimanite, and garnet, are derived from peninsular Indian rivers.

Provenance Studies of Mio-Oligocene Bhuban Sandstones of Surma Group in and around Kolasib, Mizoram, India

Benjamin L Chhangte — 2026-06-30

Mizoram is located in the Indo-Burmese tectonic collision zone in the easternmost corridor of the Indian subcontinent, bordering Myanmar to the east and south and Bangladesh to the west resulting in a complex tectonic framework. The region geologically comprises of Oligocene to Miocene sedimentary strata of Surma basin which are texturally and mineralogically immature. In order to enhance the current state of knowledge on the petrogenesis of the sedimentary terrain of this region, the present work deals with the provenance of Mio-Oligocene Bhuban sandstone of Bhuban Formation, Surma Group, around Kolasib in the northwestern section of Mizoram with the help of petrographic and geochemical analyses. Identification of detrital grains and mineral modes in thin section was carried out using LeicaDM4500 P polarizing microscope equipped with Leica DFC420 camera and Leica Image Analysis software (LAS- v4.6). A Gazzi-Dickinson point counting method was employed during modal analysis. Geochemical analyses include major-minor oxides, trace elements and REEs. Results of petrographic and geochemical analyses were plotted in various binary and ternary discrimination diagrams to find out the geological history of the rocks. Detailed petrographic examination indicates that the detrital quartz grains dominate the framework mineral which was followed by rock fragments and feldspars. The classification indicated lithic to sub-lithic arenite of moderate to poorly sorted, fine- to very fine grains. The petrographic analysis eventually confirmed mineralogical and textural immaturity. Based on the petrographic and geochemical studies, rocks of the study area are derived from mixed source ranging from igneous to metamorphic rocks and recycled sedimentary rocks, dominated by felsic igneous and low rank metamorphic sources which were deposited under sub-humid climatic condition in the geological past.

Delineation of Depositional Environment from Quaternary Sediments in Lendi River Sub-basin, Maharashtra, India

Chandrakant Gurav — 2026-06-30

The grain size analysis of Quaternary sediments from the Lendi river sub-basin in Latur and Nanded districts of Maharashtra has been carried out to investigate the textural parameters and statistical measures to understand the depositional environment. A total thirty-three samples were collected during the fieldwork. These samples were meticulously analyzed using British Standard Sieve (BSS) method. The grain size analysis clearly shows that the differential sorting of grains reflects significant changes in environment throughout geological history. Coarse sediments are prominently deposited over the country rock, forming a solid foundational layer. Above the coarse sediment formation, there are well defined formations of sand and silty clay deposited. Similarly, the presence of cross bedding and graded bedding structures clearly indicate the fluctuation in climatic conditions that have occurred over time. The depositional environment of coarse gravel sediments in the bottom beds of Lendi river at Halni, Mukaramabad and Ravangaon indicates that the streams possess relatively high energy with prevalent bed load transport; whereas fine clay and silt at Hanuman, Hipperga, Gojegaon and other places in the upper layer reflect that the streams are of low gradient, influenced by seasonal variations in climate.

A comparative study on the petrography, provenance and tectonic settings with evolution patterns with the Neogene Lithosequence in the Siwalik Belt, Arunachal Pradesh and the Belt of Schuppen, Naga-Patkai Hills, India

Abhijit Chakraborty — 2026-06-30

This study presents a comparative analysis of Neogene sandstones from two tectonically active regions in Northeast India-the Siwalik Belt of Arunachal Pradesh and the Belt of Schuppen in the Naga-Patkai Hills. Petrographic examination of 40 thin sections (20 from each region) was conducted to assess mineralogical composition, provenance, and tectonic implications. Quartz is the dominant framework grain, ranging between 48% and 56.6%. Variations in quartz texture, particularly the proportion of undulatory monocrystalline and polycrystalline types, reflect differing degrees of tectonic compaction and sediment recycling. Mica content, especially the presence of kink-banded muscovite, further indicates deformation intensity during burial.

In the Schuppen Belt, Tipam Sandstones at Tipong-Pani contain more sedimentary fragments, while Namchik-Namphuk samples are richer in metamorphic and igneous clasts, consistent with rapid uplift of the Mishmi Hills. In contrast, the Siwalik Belt samples from Kimin-Ziro and Likabali-Garo show higher proportions of undulatory quartz and metamorphic fragments, pointing to a recycled orogenic source from the Higher and Lesser Himalayas. Feldspar textures and matrix content suggest variable depositional energy across the formations.

Provenance plots (QFL and QmFLt) confirm a quartzose recycled origin for both belts. These mineralogical signatures, particularly the deformation textures in quartz and mica, offer insights into the tectono-sedimentary evolution of the Himalayan foreland and associated orogenic systems during the Neogene.

Origin and Depositional Environment of Elongated Nodules Associated with the Bhander Limestone of the Vindhyan Supergroup around Rewa, Central India: Constraints from Mode of Occurrence, Optical Microscopy and Stable Carbon and Oxygen Isotopic Compositions

D. P. Dubey — 2026-06-30

The results of investigations on nodules hosted in dark grey Bhander Limestone of the Vindhyan Supergroup from the Rewa area, Central India, are presented. The nodules are either exposed on the surface of the limestone bed or covered by a calcareous layer, making the surface uneven. The material forming nodules is harder than the host limestone. The majority of the nodules are elongated (<4 cm to 2.23 m long) and broader on one side and tapering on the other side. When broken, many calcareous nodules revealed dark scaly organic material in their centre, which, in some cases, changed into black organic material, imparting black color to the host limestone. Optical microscopy revealed the presence of elongated organic materials and segmented, including indeterminate, forms within the nodules. It is interpreted that the scaly material formed a nucleus for the precipitation, and the decomposing organic material provided local chemical conditions in the pore waters, which favoured precipitation of calcium carbonate (CaCO₃) following the elongated shape of the organic material. Development of large-scale pits and pores on the limestone surface may be chitinous material, which is a fibrous organic substance known from most arthropods and many invertebrates, and also known to survive over hundreds of millions of years. It is likely that chitinous material on small pits and pores on the limestone surface was later hardened by calcium carbonate precipitation. The ¹³C (proxy of organic matter) values of nodules also indicate depletion of ¹³C, which is consistent with the influence of the organic-rich matter sources. This interpretation is further supported by the presence of eurypterid and trilobitid impressions in the study area. Chertification of some calcareous nodules is due to occasional precipitation of silica. Significantly, carbonaceous megafossils from the Bhander Group are known from other areas also, and the investigated nodules are from the youngest Bhander Group of the Vindhyan Supergroup. The covariance plots (¹³C-¹⁸O), depleted carbon and oxygen isotopes (¹³C, ¹⁸O), palaeosalinity and palaeotemperature collectively reveal formation of nodules in a supergene freshwater diagenetic environment under very shallow burial depth.

Sea-level rise, storms, and fate of barrier islands: Lessons from more than fifty years of research

Naresh Kumar — 2026-06-30

More than 2,000 barrier islands line the world's shorelines. Along the US East Coast and the Gulf of Mexico, barrier islands line almost two-thirds of the coastline. About half of the barriers worldwide are being eroded mostly as a result of sea-level rise. As a consequence, one of two scenarios might happen: the barriers regress landward as the sea-level rises (shoreface retreat) or the barrier may be overwhelmed by waves during a major storm event and may be "drowned in place". Both of these scenarios have taken place along the US East Coast during the last 8,000 years of sea-level rise.

Sea levels may rise by up to a meter by the end of the 21st century, thus endangering coastlines worldwide. Moreover, during the last few decades the population living full time or part time on these islands has increased tremendously. While the impulse is to “replenish or restore the beach” after each major natural disaster, the results are always short term. In the long term, only engineered retreat towards the land or complete abandandoment might be the only solutions. However, rather than responding to each natural disaster one-by-one as it affects the barriers, a national plan, with state-, and local-level buy-in needs to be implemented now.

Sedimentological studies of Katesar Member (Late Jurassic), Jhuran Formation, Kachchh basin: An example of transition from Delta Front to Delta Plain settings

Poonam Mangtani — 2026-06-30

The Kachchh Basin of western India preserves a thick Mesozoic succession deposited in a pericratonic rift setting along the northern margin of the Indian plate. Within this succession, the rocks of Late Jurassic Jhuran Formation comprising 4 members: lower, middle, upper and Katesar records extensive siliciclastic deposition. The present investigation is aimed to understand the nature of sedimentation and decode sedimentary environment of Katesar member using facies analysis, petrography, heavy mineral assemblages, bulk mineralogy and geochemical proxies. The facies analysis of Katesar member indicates presence of hummocky cross-stratified sandstones, bioturbated ferruginous sandstones, thin-bedded sandstone–siltstone alternations, and gypsiferous shale reflecting deposition in a wave-dominated delta front environment under episodic storm influence. Heavy mineral suites and bulk mineralogical data indicate sediment derivation from felsic sources with evidence of recycling. The geochemical analyses of major, minor, and trace elements further support a continental arc to passive margin provenance with signatures of moderate chemical weathering in the hinterland. The results obtained from these proxies have provided a refined reconstruction of sediment dispersal pathways, provenance and depositional dynamics of the Katesar member. They further highlight the progressive transition from delta-front to delta-plain environments, offering new perspectives on deltaic evolution in the Kachchh basin during the Late Jurassic period.

Report of the Field workshop on “Depositional dynamics and their role in sequence development, Vindhyan Supergroup, central India” under the aegis of Indian Association of Sedimentologists (IAS), 16th -20the February, 2026

Subir Sarkar — 2026-06-30

The Field workshop on “Depositional dynamics and their role in sequence development, Vindhyan Supergroup, central India” organized under the aegis of the Indian Association of Sedimentologists (IAS) from 16.02.2026 to 20.02.2026. The primary goal of this workshop is to enhance participants’ understanding of sedimentation dynamics and their role in sequence development within the extensive Vindhyan succession. In order to achieve the objectives of this programme, carefully selected, well-preserved, and well-exposed sections of the Vindhyan Supergroup were studied, as they provide a comprehensive archive of Proterozoic sedimentary processes. The study addressed both carbonate and siliciclastic rocks, as well as the processes through which these two sedimentary systems may interact and mix in nature. The majority of the sections were chosen for this purpose are exposed in and around Maihar, central India. The uppermost formation of the Lower Vindhyan Group, along with the entire Upper Vindhyan formations and members, is well exposed near Maihar and was examined during our field sojourn. Certain localities showcase excellent exposures of representative sections, offering clear insights into specific formations and members. A key focus was on correlating the causal factors influencing processes, thereby providing insights into basin evolution. Altogether 26 participants including faculties and research scholars joined in the field workshop. The participants included teachers and Research scholars from IIT(ISM) Dhanbad, IISER Bhopal, IIT Bombay, IIT Kharagpur, IIT Gandhinagar, Manipur University, Jadavpur University, University of North Bengal, Durgapur Govt. College, Presidency University, PRL Ahmedabad and BSIP Lucknow.

A Report on the 41st Annual Convention of the Indian Association of Sedimentologists (IAS-2025) and National Conference on Sedimentology with an Emphasis on the Impact of Deccan Volcanism on Sedimentation, Stratigraphy, Climate and Tectonics (IDSSCT) 19th

Milind Herlekar — 2026-06-30

The three-day (19^th–21^st January, 2026) National Conference on Sedimentology with an emphasis on the Impact of Deccan Volcanism on Sedimentation, Stratigraphy, Climate and Tectonics (IDSSCT) was held at the Department of Geology, Savitribai Phule Pune University, Pune-411007. The main conference featured eleven scientific themes and a total of 127 abstracts were received. A total of 12 special talks and keynote addresses were delivered by leading and active researchers. It also featured a major poster session with 29 displays, presented largely by young researchers from various Indian universities and research institutions. Many new findings within the eleven themes of the conference. The presentations highlighted the exploration of modern sedimentary environments, provenance and depositional conditions, facies architecture, their stratigraphic relations, basin evolution, and the sedimentology of Quaternary archives. climatic environment and disaster-related issues, nuances of ancient Earth, understanding the forces beneath our planet's surface, decoding transitional continental and marine depositional systems, basin evolution and examining the biological processes influencing sedimentation.