Microfossils from the Neoproterozoic Gangolihat Formation, Kumaun Lesser Himalaya: Their stratigraphic and evolutionary significance

Tiwari, Meera; Pant, Indu

doi:10.1016/j.jseaes.2009.01.008

Cited by 16 publications

(4 citation statements)

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“…These small fossils are mostly globular, with a few that are tubular, and reportedly have preserved evidence of former soft parts in the phosphatic replacements. Other possibly Vendian spicules have been reported by TIWARI, PANT, and TEWARI (2000) from the Lesser Himalayas, northern India, where isolated hexactines have been observed in the Gangolihat Dolomite.…”

Section: Precambrianmentioning

confidence: 70%

Part E, Porifera (Revised), vol. 2, Complete Volume

Rigby

Reid

2016

InvertebratePaleo

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Section: Precambrianmentioning

confidence: 70%

Part E, Porifera (Revised), vol. 2, Complete Volume

Rigby

Reid

2016

InvertebratePaleo

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“…The present study area which belongs to the Thalkedar limestone unit of Mandhali Formation, Tejam Group of Lesser Himalaya, district Pithoragarh possesses complexly folded sequence of limestone and slate. On the basis of presence of microfossils, Tiwari and Pant (2009) consider the Gangolihat Limestone of Kumaon Himalaya as Neoproterozoic age. The folding in these Neoproterozoic rocks must have been developed in multiple phases during the Himalayan Orogeny in Tertiary.…”

Section: Discussionmentioning

confidence: 99%

Geometric and strain analyses in folds of the area around Gankot, district Pithoragarh, Uttarakhand, India

Lata¹,

Kumar²,

Srivastava³

2019

J. Geoscience Eng. Environ. Technol.

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The study area around Gankot in Pithoragarh district of Uttarakhand belongs to the Thalkedar Limestone unit of Mandhali Formation, Tejam Group in Inner Sedimentary Zone of Lesser Himalaya, which exposes complexly folded and refolded structures. Geometric analysis carried out on the profile section of the fold tracing using dip isogon and orthogonal thickness parameters revealed presence of all the fold geometry suggested by Ramsay (1967) however the class 3 followed by class 1B are the most dominant classes in the study area when individual layers of the fold were studied. The study of folds as multilayered unit reveals that folds in study area belong to strongly non-analogous fold class of anisodeviatoric folds. In fold, the strain analysis has been done by drawing strain ellipse obtained by Inverse Thickness Method which is useful in estimating flattening strain even when the flattening is imposed obliquely to the fold’s axial trace. The finite two-dimensional flattening strain ratio (Rs) value ranged between 1 and 3.14 with an average Rs value of 1.60. The method of Srivastava and Gairola (2003) has also been used to obtain shear strain and flattening strain for the multilayered folds of study area. The results reveal that the multilayered folds around Gankot area are moderately flattened with mean flatting strain varying between 1.06 and 2.28. A very high degree of variation in shearing ranging about 70o in both clockwise and anticlockwise directions has been noticed. The shear strains (γ) in folds have been found to vary between -2.75 to + 3.27 with an average of +0.33. The shearing and strain patterns are suggestive that the most dominant folding mechanism has been the flexure-shear for the folds of the study area which are overprinted by the fold flattening and other subsequent deformations.

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“…Although reports suggest the Tindir Group spicule-like structures were originally hollow and are comparable to chancellorid sclerites (Allison and Awramik, 1989), they have not received sufficient study to affirm sponge affinities. Other problematic hexactinellid spicules have been reported from the Gangolihat Dolomite of India (Tiwari et al, 2000;Tiwari and Pant, 2009). Most of these Gangolihat Dolomite structures are opaque, and thus do not resemble typical siliceous hexactinellid spicules in thin-sections.…”

Section: Implications For Other Purported Precambrian Spongesmentioning

confidence: 94%

Assessing the veracity of Precambrian ‘sponge’ fossils using in situ nanoscale analytical techniques

Muscente

Michel

Dale

et al. 2015

Precambrian Research

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Paleontological inferences, molecular clocks, and biomarker fossils indicate sponges evolved in the Cryogenian, but Precambrian sponge fossils are rare, poorly substantiated, and controversial. Spicule-like microstructures (SLMs) hosted in phosphatized fossils from the Ediacaran Doushantuo Formation (~635-551 Ma) at Weng'an of South China have been interpreted as cylindrical siliceous monaxons, and their hosting fossils as the oldest demosponges in the fossil record. In order to assess their veracity as the oldest spiculate demosponges, we utilize a suite of in situ nanoscale analytical techniques-including scanning electron microscopy, synchrotron Xray fluorescence mapping, X-ray absorption near edge structure (XANES) spectroscopy, focused ion beam electron microscopy, and transmission electron microscopy-to evaluate the ultrastructures and elemental, chemical, and mineralogical compositions of the SLMs. Our data decisively shows that the SLMs are carbonaceous in composition and rectangular in transverse sections, and therefore, are not cylindrical siliceous spicules. Instead, the SLMs may be microbial strands, axial filaments of early hexactinellids, or acicular crystals molded by organic

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Microfossils from the Neoproterozoic Gangolihat Formation, Kumaun Lesser Himalaya: Their stratigraphic and evolutionary significance

Cited by 16 publications

References 50 publications

Part E, Porifera (Revised), vol. 2, Complete Volume

Part E, Porifera (Revised), vol. 2, Complete Volume

Geometric and strain analyses in folds of the area around Gankot, district Pithoragarh, Uttarakhand, India

Assessing the veracity of Precambrian ‘sponge’ fossils using in situ nanoscale analytical techniques

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