Browsing by Author "Mukund Sharma"

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A note on the Fan-Fabric Structures in the late Palaeoproterozoic Kajrahat Limestone, Katni, M.P., India
(Palaeontological Society Of India, 2021) Uday Bhan; Divya Singh; Mukund Sharma; Deepak Singh; S.K. Pandey
Present study records the Fan-Fabric Structures from the late Palaeoproterozoic Kajrahat Limestone of the Vindhyan Supergroup, India exposed in Katni district, M. P. Centimeter (cm) size carbonate fans (1 to 10 cm in length) radiating in upward direction are part of a stromatolite dominated Kajrahat Limestone in the area. The Kajrahat FFS represent their wide-spread occurrence in the Proterozoic successions of India. Our study establishes that these fans were originally precipitated and not the result of a late diagenesis or any other post sedimentation process. These fan-fabric structures were deposited in intertidal to sub-tidal environments. Globally, fan-fabrics structures are considered a common feature of the Archaean to early Mesoproterozoic carbonate platforms. © 2021 Palaeontological Society Of India. All rights reserved.
Carbonate Fan Fabric Structures (FFS) in time and space: A case study from the Palaeoproterozoic Kajrahat Limestone, Vindhyan Supergroup, India
(Palaeontological Society Of India, 2021) Divya Singh; Mukund Sharma; Uday Bhan; Bindhyachal Pandey; S.K. Pandey; Deepak Singh
This paper describes and discusses the origin of the carbonate Fan Fabric Structures (FFS), a rare and typical feature of the Precambrian Eon, observed in the Kajrahat Limestone near the Kota area, Sonbhadra District, Uttar Pradesh, India. In the Kajrahat Limestone, FFS escaped later recrystallization and subsequent dolomitization which otherwise obliterates the depositional texture as noted in most of the Proterozoic carbonate deposits. Characteristic FFS is noted exclusively in the upper part of the Kajrahat Limestone, Semri Group, Vindhyan Supergroup. The FFS varies from microscopic to mesoscopic in size. The depositional environment of the hosting carbonate units is inferred with the help of FFS morphology and configuration. The absence of actual microfossils, however, is conspicuous suggesting very rapid lithification. The origin of aragonite crystals and the possible role of organisms in the formation of FFS are discussed. The study reveals that these carbonate fans were formed below the sediment-water interface by the interplay of sedimentation and vertically upward nucleation of the crystal. Low diversity of stromatolites is also present in the Kajrahat Limestone and the overlying Salkhan Limestone. The Rohtasgarh Limestone, the top-most unit of the Lower Vindhyan is, however, completely devoid of FFS and stromatolites therefore, it is inferred that the FFS are restricted in time and space. © 2021 Palaeontological Society Of India. All rights reserved.
First observation of microspherule from the infratrappean Gondwana sediments below Killari region of Deccan LIP, Maharashtra (India) and possible implications
(Elsevier B.V., 2019) G. Parthasarathy; O.P. Pandey; B. Sreedhar; Mukund Sharma; Priyanka Tripathi; Nimisha Vedanti
A rare occurrence of a microspherule has been found in the infratrappean sediments, encountered below 338 m thick Deccan volcanic cover in KLR-1 scientific borehole, drilled in the epicentral zone of the 1993 Killari earthquake (Maharashtra, India). Palynological studies of the sediments indicate their age as Early Permian (Asselian, 298–295 Ma) for deposition. Transmission electron microscope studies reveal that the spherule from the infratrappeans, is having a similar composition to that of the Neoarchean amphibolite to granulite facies mid crustal basement. The spherule is non-spherical in nature, containing mostly FeO (10.70 ± 0.20 wt.%), CaO (13.8 ± 0.5 wt.%), Al2O3 (7.78 ± 0.30 wt.%), MgO (6.47 ± 0.3 wt.%), SiO2 (47.46 ± 0.50 wt.%), TiO2 (2.47 ± 0.3 wt.%), K2O (1.89 ± 0.20 wt.%), and Cl (0.33 ± 0.05 wt.%). Since the Fe composition of the spherule is almost same as the basement rock (10.5 wt.%), and the chlorine content is also in the same range as the basement (0.04–0.24 wt.%), it would suggest possibility of an extraterrestrial impact over the Indian terrain during the erstwhile Gondwana sedimentation period that may be associated with the Permian–Triassic mass extinction, the most severe one in the Earth's history. © 2019 China University of Geosciences (Beijing) and Peking University
Geochemistry and Petrogenesis of Mesoproterozoic Mafic Intrusive Rocks from the Singhora and Chandarpur Groups, Eastern Chhattisgarh Basin, Bastar Craton: Possible Implication for the Time of Sedimentation
(Springer, 2022) Ankur Ashutosh; Amiya K. Samal; Veeru Kant Singh; Mukund Sharma; Rajesh K. Srivastava
A number of Mesoproterozoic mafic intrusions transect the Chhattisgarh basin, Bastar craton, and they are mostly exposed in the Singhora and Chandarpur Group of rocks in the eastern part of the basin. These mafic intrusive rocks are studied for their petrological and geochemical characteristics to understand nature and genesis and likely implication on the time of sedimentation. They chiefly consist of clinopyroxene and plagioclase and show ophitic texture. Geochemically, they are sub-alkaline basalt to basaltic andesite and strongly supports cogenetic nature of mafic intrusives from both the Groups. The fractionation of olivine, clinopyroxene, plagioclase and Cr-spinel primarily controlled geochemical variations. Negative Nb−Ta−Ti anomalies suggest a possible role of crustal components in the evolution of the melt; however, the absence of crustal signature in most primitive high-Mg containing samples rules out any significant role of crustal contamination. Incompatible trace elements modelling suggests their derivation from a mantle melt, originated from the transition zone of garnet-spinel stability field. Further, geochemical analysis supports an SZLM (subduction zone-modified lithospheric mantle) source for these mafic intrusions. Low CaO/MgO (1.20–1.64), intermediate FeO/MnO (45.71–71.80), positive PX# (1.10–5.89), and high values of FC3MS (0.58–1.35) and FCKANTMS (0.59–0.93) explicitly support derivation of the primary melt from a olivine-poor and pyroxene-rich (pyroxenite type) source. The observed geochemical characteristics and published age data on these mafic intrusions indicate that sediments of both the stratigraphic units are older than ca. 1.42 Ga. Further, based on the relationship with the neighbouring ca. 1.85 Ga Sonakhan mafic dyke swarm of the Bastar craton, the age of sedimentation in the Chhattisgarh basin has been proposed to be in between ca. 1.85 Ga and 1.42 Ga. © 2022, Geological Society of India, Bengaluru, India.
Observations on the ichnospecies Monomorphichnus multilineatus from the Nagaur Sandstone (Cambrian Series 2-Stage 4), Marwar Supergroup, India
(Springer, 2018) Mukund Sharma; S.K. Pandey; S. Ahmad; K. Kumar; A.H. Ansari
The Ediacaran–Cambrian Marwar Supergroup exposed in the western Rajasthan, India yielded abundant sigmoidal scratches assigned to ichnospecies Monomorphichnus multilineatus from the Nagaur Sandstone belonging to the Cambrian (Series 2-Stage 4). Nagaur M. multilineatus are recorded from the intertidal regime. It is an addition to already known depositional environments for this ichnospecies, which are known from shallow marine, wave-dominated, to non-marine or brackish water and storm-dominated sequences. Classical systematics of M. multilineatus is enriched with additional information in the paper. Its significance has been discussed regarding the palaeoecology of trace producers. Comprehensive statistical analyses help reveal its behaviour and feeding pattern of the causative organism of M. multilineatus. Hierarchical Cluster Analysis (HCA), average linkage and Pearson Correlation were performed to establish the natural grouping and behaviour of the specimens. HCA indicates that the studied Nagaur specimens belong to ichnogenera Monomorphicnus and ichnospecies, i.e., multilineatus. Pearson correlation, involving thickness and length of individual specimen, was positive. It indicates that the amount of food required by individual adult specimen was more and thereby requiring more grazing to provide enough food for survival. All the known occurrences of M. multilineatus are reviewed in the present study for their mode of preservation, depositional environment, palaeoecology and taphonomy. © 2018, Indian Academy of Sciences.
On the ichnofossil treptichnus pedum: Inferences from the nagaur sandstone, marwar supergroup, India
(Czech Geological Survey, 2018) Mukund Sharma; Shamim Ahmad; Santosh K. Pandey; Kuldeep Kumar
Sandstone-mudstone interfaces offer an excellent medium for the preservation of the burrows. This study discusses the morphology, ecological niche and correlation based of 291 Treptichnus pedum specimens of the lower Cambrian Nagaur Sandstone, western Rajasthan, India. Petrological attributes of the host sediment are also addressed. Statistical analyses of size (length, width and gap of each segment of T. pedum) were conducted to determine the inter-specific variation. Data suggest that the entire Nagaur assemblage was made by one major group of makers. Overall morphology suggests that these burrows were probably made for shelter and trapping small epibenthic or endobenthic organisms. An overview of the global occurrence of T. pedum shows broad environment tolerance. The Nagaur specimens are compared with various recorded occurrences of T. pedum to assess the nature of the plausible producer organism, itsbehaviour and taphonomical aspects. © 2018, Czech Geological Survey. All rights reserved.