Time filter

Source Type

Panchkula, India

Ghosh N.,University of Texas at Arlington | Basu A.R.,University of Texas at Arlington | Bhargava O.N.,INSA Honorary Scientist | Shukla U.K.,Banaras Hindu University | And 3 more authors.
Gondwana Research | Year: 2015

Interpreting global consequences of the Permian-Triassic (P-Tr) extinction requires examination across paleogeographic realms of Pangaea. The Spiti Valley in India, remnant of the peri-Gondwanan shelf, preserved trails of this environmental catastrophe in the Neo-Tethys Ocean. We document new sedimentological observations and high-resolution trace element concentrations and carbon, oxygen, lead isotope data across the P-Tr boundary in Spiti. Framboidal pyrites, fossils and laminated lithology of the Late Permian shales indicate deeper anoxic depositional environment while δ13Corg excursions of 2.4‰ and 3.1‰ in Atargu and Guling outcrops, respectively, identify the P-Tr transition across a clayey, partly gypsiferous ferruginous layer. Sedimentological similarities of this layer to other Neo-Tethyan sections from Transcaucasia and Iran indicate subaqueous oxidation of shallow marine sediments on a regional scale. Light Rare Earth Element - enriched Late Permian shales with conspicuous Ce-Eu anomalies reflect their source from the adjacent Panjal Trap basalts (ca. 289Ma) of Kashmir. Continental crustal Nb-Ta and Zr-Hf anomalies appear at the P-Tr boundary sediments, and prevail through the overlying Early Triassic carbonates. Original Pb isotope ratios, along with an increasing Pb abundance closer to the P-Tr boundary, distinguish the volcanic source of the Late Permian shales from the continental crustal siliciclastic signature of the Early Triassic carbonates. Our δ13Corg, trace element and Pb isotope record from Spiti indicate catastrophic changes in sediment sources and facies, with effects on carbon cycle and are consistent with an abrupt episode of marine regression and erosional forcing, also observed elsewhere along northern Gondwanaland. Simultaneous eruption of Siberian volcanics and bolide impacts in Parana basin of Brazil and elsewhere implicating impact-triggered volcanism, left catastrophic regional-global imprints on sea level, climate, marine anoxia and tectonic stability that connected the P-Tr crisis across terrestrial and marine realms worlwide. © 2014 International Association for Gondwana Research. Source

Sridharan A.,INSA Honorary Scientist
Geotechnical and Geological Engineering | Year: 2013

The coefficient of permeability of stratified soil deposits, when the flow is normal to the orientation of the bedding planes, has been observed to deviate from the value calculated theoretically. This deviation has been successfully explained in the past for a two-layer soil system by considering the coefficient of permeability of the exit layer as the controlling factor. The present technical note deals with the results from the study of permeability behavior of three-layer soil system. This study reinforces the point that the coefficient of permeability of a layered soil system, when the flow is normal to the orientation of the bedding planes, depends upon the relative positioning of the layers with different values of coefficient of permeability in the system. © 2013 Springer Science+Business Media Dordrecht. Source

Singh B.P.,Panjab University | Chaubey R.S.,Panjab University | Bhargava O.N.,INSA Honorary Scientist | Prasad S.K.,Panjab University | Negi R.S.,Panjab University
Palaeoworld | Year: 2016

The Cambrian trilobite fauna, illustrated for the first time from the Pin Valley (Spiti, Northwest Himalaya, India), comprises Oryctocephalus indicus, Pagetia significans, Kunmingaspis pervulgata, and Bhargavia prakritika and they ranges from the top part of the Cambrian Series 2 (Stage 4) to the basal most part of the Series 3 (Stage 5). On the basis of the trilobite fauna and their stratigraphic order of occurrence we recognize the Oryctocephalus indicus Zone (5.4. m), interval 1 of no zonation, and the Bhargavia prakritika Level (Cambrian Series 3, Stage 5). The Oryctocephalus indicus Zone is based on the FAD and LAD (local range) of the eponymous species in the Pin Valley section. The occurrence of fossiliferous section immediately below the Cambro-Ordovician angular unconformity in the Pin Valley indicates, in comparison to the Parahio Valley, nearly 1160. m of the Cambrian strata (deposited within about 2. Ma, i.e., 509 to 507. Ma) further eroded prior to the deposition of the Thango Formation. © 2016 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. Source

Sridharan A.,INSA Honorary Scientist | Prasanna H.S.,Indian National Institute of Engineering
Geotechnical and Geological Engineering | Year: 2014

In order to realize more benefits and to have more effective output from the mechanical ground improvement projects, the field soils are subjected to over consolidation. This process induces a characteristic yield stress in the compacted soil mass similar to that exhibited by the soil masses subjected to natural processes of over consolidation during their geological life time. In view of the absence of any documented geotechnical engineering literature on such an important topic, this paper intends to throw some useful light on compaction induced yield stress in fine-grained soils. A detailed discussion of various factors contributing to the induced yield stress as a consequence of compaction is done. The results of the present experimental study indicates that the values of compaction induced yield stress increase from dry side of optimum to optimum compacted state. This stress may tend to achieve an equilibrium value or decrease beyond optimum compacted state depending upon the contribution from the coarser fraction composing the soil. It is also illustrated that the soils subjected to same compactive effort exhibit different values of yield stress as a consequence of clay mineralogical composition of the soils. © 2013 Springer Science+Business Media Dordrecht. Source

Narain P.,INSA Honorary Scientist
Proceedings of the Indian National Science Academy | Year: 2014

A general theory of transmission/disequilibrium test (TDT), given the information on an arbitrary number of markers on the two parents and their child, affected by the disease is developed. With k biallelic SNP markers and N=2k types of possible haplotypes we consider a N × N table of transmission events in which A/diagonal elements correspond to homozygous transmissions, not relevant to the problem of testing linkage, and N(N-I) off-diagonal elements resulting in N(N-l)/2 matched pairs of transmissions. This gives rise to N/2 chi-square tests, corresponding to different phases of the A-tuple heterozygote, each based on I d.f. on the null hypothesis of no linkage between the disease-susceptibility gene and all the k markers jointly. The power of the test, in terms of non-centrality parameter, has been derived algebraically for k-1 and 2 and studied numerically to show that tighter linkage results in higher power. Two pairs of markers give higher power over single marker case. The theory has been validated with the help of simulated data on 4 markers with 500 trios. Possible future investigation on TDT with two adjacent linked QTLs following risk of duplicate dominant epistasis type and involving a single marker has been indicated. Source

Discover hidden collaborations