http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/195 Thu, 30 Oct 2025 07:08:49 GMT 2025-10-30T07:08:49Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1103 Title: Petrography of Barail sandstone of ChamphaiMualkawi section in Champhai district, Mizoram: Implication on provenance and tectonic setting Authors: Hauhnar, Malsawmtluangkima Abstract: The area around Champhai district contains exposed Barail Group of rocks (Oligocene) which comprises of buff-coloured sandstones with alternating beds of shale and siltstone. This study focussed on the provenance and tectonic setting of the Barail sandstones with the help of detailed petrographic studies and quantitative and qualitative modal analysis by point counting technique. The general lithological units consist of sandstone, shale, crumpled shale, silty-shale and siltstone. A modal analysis of the 25 sandstone samples was carried out on selected detrital grains like quartz, feldspar and lithic fragments which indicated that quartz ranges between 69.75 to 82.25%, feldspar ranges between 1.80 to 6.91% and lithic fragments ranges between 13.82% to 29.43%. The sandstones belong to sublitharenite, litharenite and feldspathic litharenite indicating predominant presence of quartz in the sandstones with lesser components of feldspar and lithic fragments. Different variants of quartz such as undulatory monocrystalline quartz and polycrystalline quartz and other lithic fragments like schist and gneiss indicate metamorphic source rock. The common occurrence of micas in almost all the sandstone samples may also indicate the common occurrence of mica-bearing metamorphic schists or gneiss in the provenance. Various characteristics of feldspar like strong alteration in orthoclase, deformed twinning of plagioclase and presence of micas may be indicative of low to high grade metamorphic rocks and acidic to basic igneous rocks. On the basis of different tectonic discrimination diagram using QFL and QmFL, the tectono-provenance of the sandstones was found to be Quartzose Recycled Orogen. It is concluded that the source area might be the tectonically active continent-continent collision zone of eastern Himalaya and the Indo-Burmese belt and that the associated extrusive and intrusive igneous rocks are prone to weathering and erosion by various denudation processes. Mon, 01 Jan 2018 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1103 2018-01-01T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1102 Title: Geochemistry of Barail sandstone in Champhai, Mizoram: Implications on provenance and weathering history Authors: Hauhnar, Malsawmtluangkima Abstract: Mizoram is geologically young comprising entirely of sedimentary rocks. The Oligocene age of Barail group of sedimentary rocks, exposed near the Indo Myanmar mobile belt, i.e., Champhai area, Mizoram have been studied to infer the provenance and paleoweathering history. The significance of the work is that it will uncover and reconstruct origin of Barail sandstone and restore the tectonic and paleoclimatic conditions based on petrography and geochemistry of the sandstone. The geochemical classiBcation based on diagrams of log(SiO2/Al2O3) vs. log(Na2O/K2O) and log(SiO2/Al2O3) vs. log(Fe2O3/K2O) of the Barail sandstones indicated that the sandstones belong to litharenite and wacke. The geochemical characteristics of the rock are plotted in various binary and ternary diagrams and selected ratios of elements are interpreted in the light of source rock characteristics. The Chondrite normalised REE pattern show similar pattern to UCC (Taylor and McLennan 1985) with an enrichment of LREE and depletion of HREE. The ratio of Al2O3/TiO2 and the ternary diagram of La–Th–Sc indicate felsic to intermediate source. Similarly, the high LREE/HREE ratios and negative Eu anomaly (La/Lu)cn, ratios of Eu/Eu*, La/Sc, La/Co, Cr/Th, Th/Sc, Th/Co and Cr/V ratio indicate felsic source. The binary diagram between ratios of Zr/Sc vs. Th/Sc inferred volcanic source. The sediments are also found to be derived from recycled sedimentary rock which is proved by ratios of Zr/Sc and Th/U. The A–CN–K diagram and weathering indices such as CIA, PIA shows moderate to intense weathering in the source area. The investigated Barail sandstones are chemically mature as indicated by the ICV while the ratio of SiO2/Al2O3 indicated moderate sediment maturity. Tue, 29 Sep 2020 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1102 2020-09-29T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1035 Title: A Comparative Study of Ichnofossils from Upper and Middle Bhuban Unit of Bhuban Formation (Surma Group), Aizawl, Mizoram to Decipher the Depositional Environment Authors: Lalremruatfela, C Abstract: Objectives: The aim of the present study is to interprete and compare depositional environment of Upper and Middle Bhuban rocks from its trace fossil content. Methods: The trace fossils collected from the Upper and Middle Bhuban Formation are studied group wise up to species level for their systematic paleontological description with the help of type material and available literature in the laboratory. Distribution pattern of trace fossils in the sediments such as orientation, diversity, mode of preservation, relationship with the host sediments are also collected in order to interprete the depositional environment. Findings: Ichnological analysis of Upper Bhuban and Middle Bhuban Unit has been attempted to decipher the palaeoenvironment. The Upper Bhuban Unit are represented by a diverse lithofacies comprises of sandstone, shale and silty-sandstone with the presence of wavy sedimentary structure and parallel lamination. A total of 12 ichnospecies found in Upper Bhuban Unit belongs to Skolithos, Cruziana and mixed Skolithos – Cruziana ichnofacies. Phycosiphon isp. is reported for the first time in North-East India. Middle Bhuban Unit exposed along Zuangtui section comprises ~40m thick sequence of sandstone, siltstone and shale.17 ichnospecies belonging to Skolithos, Cruziana, Teredolites and mixed Skolithos – Cruziana ichnofacies has been identified along this section. Diplopodichnus is reported for the first time from the Surma rocks of Mizoram as well as other Miocene successions in India. Presence of Teredolites ichnofacies indicates marine margin environment, Skolithos ichnofacies indicate sandy shifting substrate and high energy conditions in foreshore zone while Cruziana ichnofacies indicate unconsolidated, poorly sorted soft substrate and low energy condition in the shoreface/offshore zone. Novelty: Present study corroborate that Upper Bhuban rocks were deposited under shallow marine environment while Middle Bhuban rocks were deposited in a deeper, quiet water environment. Fri, 09 Jun 2023 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1035 2023-06-09T00:00:00Z http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1033 Title: Trace fossil assemblage of Oligocene (Barail Group) from Zote Area, Champhai District, Mizoram Authors: Lalremruatfela, C Abstract: The Barail Group (Oligocene) of Zote section, Champhai district, Mizoram has been studied, for the first time, on the basis of trace fossil. The study areas consist of different rocks like Sandstone, siltstone, shale and their admixture in various proportion. The present paper documents 14 ichnofossils such as Arenicolites isp., Gyrolithes lorcaensis, Helminthopsis abeli, H. hieroglyphica, H. tenuis, Laevicyclus mongraensis, Lanicodichna medulata, Palaeophycus sulcatus, P. heberti, Psilonichnus tubiformis, Skolithos linearis, S. verticalis, Teichichnus spiralis and Thalasinoides paradoxicus. The different ichnoassemblages present in Zote area correspond to the Psilonichnus, Skolithos and Cruziana facies. With the analysis of Ichnofacies and lithofacies, studied rock of Barail Group exposed in Zote area is interpreted as to have been deposited under fluctuating energy condition, sandy substrate to sublittoral zone of shallow marine environment. Wed, 15 Dec 2021 00:00:00 GMT http://pucir.inflibnet.ac.in:8080/jspui/handle/123456789/1033 2021-12-15T00:00:00Z