Journal of The Indian Association of Sedimentologists (peer reviewed)

Provenance and Diagenetic Features of Sandstones in the Surma -Tipam Transitional Sequence exposed in the Schuppen Belt, Naga Hills, NE India

2023-07-16T15:24:01+00:00

The Belt of Schuppen, a significant part of Indo-Burma Ranges is basically comprised of the molasses of Tertiary age. This tectono – stratigraphic belt is restricted by two major thrust fault namely Disang thrust and Naga thrust. In the southern part of Naga Hills a significant part of the belt is occupied by Surma – Tipam Transitional Sequences (STTS). The present study deals with the petrography, provenance, tectonic setting and diagenetic changes of STTS sandstones. The sandstones of STTS belong to arkose and arkosic wacke categories. It shows a mixed provenance of sedimentary, igneous and metamorphic. The major contribution of detritus has been observed from Recycled Orogen, Dissected Arc, Transitional Continental and Basement uplift. Different diagenetic signatures observed in these sandstones such as, point, long and concavo convex grain boundary, albitization, crushing and squashing of quartz grains, warping of mica around detrital grains, kink bending of mica suggest early to a late stage deep burial diagenesis.

Petrography and geochemistry of the Upper Cretaceous Gryphaea Limestones, Kallankurichi Formation, Ariyalur Group, Trichinopoly, Southern India: Implication for palaeoenvironment

2023-09-26T01:39:57+00:00

Sub-surface Kallankurichi gryphaea limestone formation is observed between Archaean and Quaternary outcrops. Petrographic observation reveals that mega fossils are absent and it contains abundant skeletal fragments of pelecypods, gastropods, foraminifera, bryozoa, and symbiotic algae. X-ray diffraction (XRD) analyses reveal the mineralogical components of both carbonate and clay minerals. Carbonate minerals include calcite, siderite, witherite, malachite, smithsonite, and rhodochrosite. Clay minerals detected are kaolin, montmorillonite, and palygorskite. Major element composition represents predominance of CaO, SiO₂, Al₂O₃, and Fe₂O₃ oxides, while MgO, MnO, Na₂O, K₂O, TiO₂, and P₂O₅oxides are depleted. Statistical analyses of correlation coefficient, principal component analysis, and cluster analysis represent the geochemical affinities and aerial distribution similarities among major elements. Palaeoclimate inferred through biotic proxies, major element geochemistry, and clay minerals represents arid and semi-arid climate.

Textural characteristics and distribution of ostracoda in core sediments from the Gadilam river estuary, Cuddalore, Tamil Nadu, southeast coast of India

2023-10-17T18:33:39+00:00

To know the distribution of brackish water Ostracoda and to investigate the sediment characteristics, a core (105 cm) has been collected from the Gadilam river estuary and it was sub-sampled into 21 samples at 5 cm width regular interval. All the sediment samples were analyzed as per standard micropaleontological techniques in order to investigate the distribution and occurrence of ostracod fauna. A total of 27 ostracod taxa belonging to 16 genera, 12 families, 3 superfamilies and 2 sub-order of the order Podocopida, have been identified based on published articles Throughout the core (from top to bottom) the calcareous forms were noticed. The ostracod species Kalingella mckenziei and Jankeijcythere mckenziei are widely distributed in the core and they outnumbered the rest of the species. The faunal assemblages recorded are tropical, brackish to neritic (shallow marine) and benthic in nature (Hemicytheridea paiki, Hemicytheridea bhatiai, Jankeijcythere mckenziei, Kalingella mckenziei, Neosinocythere dekrooni, Paijenborchellina sp., Stigmatocythere indica and Tanella gracilis). In the analyzed core, there is no faunal assemblage at the depth between 80-85 and 95-105 cm. The sediment characteristics such as calcium carbonate, organic matter and sand-silt-clay ratio also determined and correlated with the observed ostracod populations. Based on the detailed study, it is noticed that high calcium carbonate and low organic matter of the sediment are congenial for population abundance. From the overall distribution of Ostracoda in all the subsamples, siltysand is found to an accommodative substrate for the prosperity of Ostracoda. The statistical aspect of ostracod carapace-valve ratio has been studied to identify the rate of sedimentation which infers a faster rate of deposition of sediments in the Gadilam River estuary.

Landslide susceptibility assessment along the National Highway-244 from Batote to Doda, J & K, India: A study based on the Frequency Ratio Method

2023-11-09T18:46:41+00:00

The National Highway-244 is highly susceptible to landslide occurrences, frequently resulting in road blockades and causing significant hardships for the local population. These landslides pose a threat to human lives, property and the environment, leading to substantial losses. In this study, an attempt has been made to carry out landslide susceptibility assessment through frequency ratio method along the National Highway-244 utilizing GIS and statistical computations. It considers eight parameters, which include topographical (slope, slope aspect, slope curvature, hill shade, and relief), anthropogenic (distance to road and distance to river) and geological parameters that mostly influence the occurrence of landslides in the area under investigation. The present study focuses only along National Highway-244 and data has been gathered from field visits and secondary sources. The results of the study inferred that the area under investigation falls into different susceptibility zones, namely very high, high, moderate, low, and very low, covering approximately 15%, 31%, 27%, 19%, and 8%, respectively of the total area. This study reveals that a considerable proportion, around 73%, of the study area falls within very high to moderate susceptibility zones. The conclusions drawn from this study hold significant implications for stakeholders and also provide valuable insights for future planning and infrastructure development, enabling them to make informed decisions. By considering the susceptibility zones identified in this study, stakeholders can implement appropriate measures to mitigate the impact of landslides, ensuring the safety and stability of the region.

Microtextures and trapped diatoms on quartz grain surfaces in the Acapulco Beach, Mexican Pacific: An insight into palaeoenvironment

2023-10-25T18:52:24+00:00

In this study, we report Scanning Electron Microscopy (SEM) images of quartz grains in the Acapulco beach, Mexican Pacific. The morphology of quartz grains is angular, sub-angular, sub-rounded, rounded, and well-rounded. The variations in the morphology of quartz grains are indicating both nearby and distance sources. The rounded and well-rounded grains support for a long transport distance and a distal source. Microtextures of mechanical and chemical origins are identified in quartz grains. The mechanical features include, bulbous edges (ble), elongated depression (ed), parallel striations, crater, meandering ridges (mr), arcuate steps, conchoidal fractures (cf), v-shaped marks (v-s), and broken grain. These mechanical features indicate the combination of fluvial, aeolian, and subaqueous environments. The conchoidal fractures are characteristic of crystalline rocks. Arcuate steps and meandering ridges are indicating a high wave energy. The striations on grain surfaces are due to collision between two grains, probably during an aeolian transport.

The chemical features include adhered particles (ap), solution pit (sp), silica globule, crystal overgrowth (crg), precipitation, and trapped diatoms. The solution pits and precipitation are indicating the diagenetic processes in a silica saturated coastal environment. A few grains are associated with both mechanical and chemical features, suggesting a dual environment, probably littoral and marine. Trapped diatoms identified in quartz grains are Cocconeis guttata and coccolith.

Texture and major element geochemistry of channel sediments in the Orsang and Hiren River Basins, Gujarat, India: Implications for provenance and weathering

2023-10-27T01:54:56+00:00

Size, shape, degree of sorting, and composition of sediments in the river channels are controlled by climate, lithology, weathering, sorting, and medium of transportation. The present investigation is focused on the grain-size and geochemical analysis of the channel sediments of the Orsang and Hiren river basins. Major outcrops in the study area are Archaean granites, granitic gneisses, Upper Cretaceous to lower Eocene Deccan Volcanic Basalts (DVB), Quaternary sediments and minor proportion of Proterozoic low grade metamorphic rocks. The sediments are poorly to moderately sorted, very finely skewed, suggesting its derivation from heterogenous sources, while the kurtosis value indicates a high-energy depositional environment. The sediments are with gravelly sand texture and the mean grain size is varying from 581.9µm to 1284.2µm. The DVB provenance of the Hiren river basin and granitic provenance of the Orsang river basin is clearly reflected in the texture and geochemical composition of sediments. The TiO₂ and Fe₂O₃ contents of sediments from the Hiren river basin are distinctly higher and are comparable to the basalts of the Saurashtra region of the Deccan Province. Sediments collected after Orsang and Hiren rivers confluence and from Narmada river show higher concentration of felsic sources, indicating that Orsang river's sediment supply significantly outweighs Hiren rivers. The arkosic-litharenite nature points towards less transportation and moderate chemical weathering for the Orsang river sediments. The low Chemical Index of Alteration (CIA) values (Avg. 48.45 and 56.99 for Orsang and Hiren rivers, respectively) and A-CN-K plot also suggest the supply of sediments from minimally weathered detritus under a semi-arid condition.