Revisiting the structure, age, and evolution of the Wharton Basin to better understand subduction under Indonesia

International audienceUnderstanding the subduction processes along the Sunda Trench requires detailed constraints on the subducting lithosphere. We build a detailed tectonic map of the Wharton Basin based on reinterpretation of satellite-derived gravity anomalies and marine magnetic anomalies. The Wharton Basin is characterized by a fossil ridge, dated ~36.5 Ma, offset by N-S fracture zones. Magnetic anomalies 18 to 34 (38–84 Ma) are identified on both flanks, although a large part of the basin has been subducted. We analyze the past plate kinematic evolution of the Wharton Basin by two-plate (India-Australia) and three-plate (India-Australia-Antarctica) reconstructions. Despite the diffuse plate boundaries within the Indo-Australian plate for the last 20 Ma, we obtain finite rotation parameters that we apply to reconstruct the subducted Wharton Basin and constrain the thickness, buoyancy, and rheology of the subducting plate. The lower subductability of younger lithosphere off Sumatra has important consequences on the morphology, with a shallower trench, forearc islands, and a significant inward deviation of the subduction system. This deviation decreases in the youngest area, where the Wharton fossil spreading center enters subduction: The discontinuous magmatic crust and serpentinized upper mantle, consequences of the slow spreading rates at which this area was formed, weaken the mechanical resistance to subduction and facilitate the restoration of the accretionary prism. Deeper effects include the possible creation of asthenospheric windows beneath the Andaman Sea, in relation to the long-offset fracture zones, and east of 105°E, as a result of subduction of the spreading center

Effect of Mechanical Stimuli on the Sensitivity of Mimosa Pudica Plant

'Touch me not' plant is o herb that shows sensation on touch, which is taxonomically called as Mimosa pudica. The fern like leaves close up and droop when touched; usually re-open within few minutes as a response to stimuli. Mimosa pudica reacts to mechanical stimuli with help of mechanosensitive channels. They are ideal transducers of physiologically relevant mechanical forces. The present study focus on the effect of mechanical stimuli in terms of various touch viz., human, plastic, cotton, fiber and wood on the sensitivity of Mimosa pudico plant whose leaves are at tender stage. Time taken for the leaflets to close and reopen was noted for each of the above mentioned stimuli. The t-test has shown the significant result for various mechanical stimuli. The rote of sensitivity was very high in Mimosa pudica as result of plastic touch

Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Understanding our seas: National Institute of Oceanography, Goa

The present article summarizes the research done at the CSIR–National Institute of Oceanography in 2014 in ocean science, resources and technology. Significant research has been conducted on air–sea interactions and coastal circulation, biogeochemistry, biology, marine geophysics, palaeoceanography, marine fishery, gas hydrates and wave energy. Technological advances covered topics like oceanographic tools. Major strides have been made in marine resources research and evaluation

Ar-40/Ar-39 dating of the Mumbai tholeiites and Panvel flexure: intense 62.5 Ma onshore-offshore Deccan magmatism during India-Laxmi Ridge-Seychelles breakup

Mumbai, located on the western Indian continental margin, exposes Danian-age Deccan magmatic units of diverse compositions, dipping seaward due to the Panvel flexure. The Ghatkopar-Powai tholeiitic sequence contains seaward-dipping (thus pre-flexure) flows and subvertical (thus post-flexure) dykes. We present new Ar-40/Ar-39 ages of 62.4 +/- 0.7 and 62.4 +/- 0.3 Ma (2 sigma) on two flows, and 62.2 +/- 0.3, 62.8 +/- 0.3 and 61.8 +/- 0.2 Ma on three dykes, showing that this sequence is much younger than the main 66-65 Ma Deccan sequence in the Western Ghats escarpment. The mutually indistinguishable ages of the Ghatkopar-Powai tholeiites overlap with available Ar-40/Ar-39 ages of 62.6 +/- 0.6 and 62.9 +/- 0.2 Ma for the seaward-dipping Dongri rhyolite flow and 62.2 +/- 0.6 Ma for the Saki Naka trachyte intrusion, both from the uppermost Mumbai stratigraphy. The weighted mean of these eight Ar-40/Ar-39 ages is 62.4 +/- 0.1 Ma (2 SEM), relative to an MMhb-1 monitor age of 523.1 +/- 2.6Ma (2 sigma), and indicates essentially contemporaneous volcanism, intrusion and tectonic flexure. This age also coincides with the rift-to-drift transition of the Seychelles and Laxmi Ridge-India breakup and the emplacement of the Raman-Panikkar-Wadia seamount chain in the axial part of the Laxmi Basin. Pre-rift magmatism is seen in the 64.55 Ma Jogeshwari basalt in Mumbai and 63.5-63.0 Ma intrusions in the Seychelles. Post-rift magmatism is seen in the 60.8-60.9 Ma Manori trachyte and Gilbert Hill basalt intrusions in Mumbai and 60-61 Ma syenitic intrusions in the Seychelles. The Mumbai area thus preserves the pre-, syn- and post-rift onshore tectonomagmatic record of the breakup between the Seychelles and the Laxmi Ridge-India. Voluminous submarine volcanism forming the Raman, Panikkar and Wadia seamounts in the Laxmi Basin represents the offshore syn-rift magmatism

"Teaching Biological Sciences in Schools - Application of the ""Project Method"" "

The 'Project method' of teaching is one of the oldest and most popular educational views of John Dewey-practiced worldwide in various subjects. However, the initial implementation of this method in developing countries like India had not been successful. But today, it is attracting youth and the modern society to adopt a student centered method of education. In India, Jawahar Navodaya schools and Kendriya Vidyalaya Sadans have been implementing the same as a part of their curriculum for years, which is amply documented. The present study has made an attempt to learn the application of project method in teaching biological science concepts viz., chemical stimuli on the sensitivity of Mimosa pudica.The findings from this experimentation are discussed

Detailed Structure and Plate Reconstructions of the Central Indian Ocean Between 83.0 and 42.5 Ma (Chrons 34 and 20)

International audienceThe Central Indian Ocean, namely the Central Indian, Crozet, and Madagascar basins, formed by rifting and subsequent drifting of India (now Capricorn), Antarctica, and Africa (now Somalia). We gathered a comprehensive set of sea surface magnetic anomaly profiles over these basins and revisited location and identification of magnetic isochrons between C34ny (83.0 Ma) and C20ny (42.536 Ma) using the objective analytic signal technique. We present high-resolution magnetic isochrons for 29 periods based oñ 1,400 magnetic anomaly picks. From the conjugate sets of picks, we derive two-plate finite rotation parameters for both the Capricorn-Antarctica and Capricorn-Somalia motions. These finite rotations are compared to three-plate reconstructions of the plate boundaries between the Capricorn, Antarctica, and Somalia plates, constrained by the closure of the Indian Ocean Triple junction. In general, the three-plate reconstructions slightly overrotate the reconstructed isochrons with respect to the Capricorn-Antarctica and Capricorn-Somalia two-plate reconstructions. Conversely, the two-plate reconstructions for Somalia-Antarctica slightly underrotate the isochrons compared to the Capricorn-Antarctica-Somalia three-plate reconstructions. We suspect that the discrepancies between the two-plate and three-plate methods result from the recent seafloor deformation in the Capricorn-India diffuse plate boundary and/or from the contrasted nature and geometry of magnetic isochrons at different spreading rates (i.e., magnetic structure of the three spreading centers). Three-plate reconstructions better constrain the closure of the triple junction but spread any misfit among all three plate boundaries. When enough quality data are available, two-plate reconstructions may lead to more realistic plate motion estimates from which additional geological problems can be identified and solved