A note on rare structure of fossil coralline algae from the southwest coast of India

The coralline algae (Rhodophyta) are well preserved in the sediments of the Dwarka Formation in and around Porbandar area, southwest coast of India. There are few records of the preservation of genicula in the fossil coralline algae. Three algal fragments with genicula are noted and recorded from the area.     

Modeling the effects of aerosols to increase rainfall in regions with shortage

It is well known that the emissions of hot gases from various power stations and other industrial sources in the regional atmosphere cause decrease in rainfall around these complexes. To overcome this shortage, one method is to introduce artificially conducive aerosol particles in the atmosphere using aeroplane to increase rainfall. To prove the feasibility of this idea, in this paper, a nonlinear mathematical model is proposed involving five dependent variables, namely, the volume density of water vapour, number densities of cloud droplets and raindrops, and the concentrations of small and large size conducive aerosol particles. It is assumed that two types of aerosol particles are introduced in the regional atmosphere, one of them is of small size CCN type which is conducive to increase cloud droplets from vapour phase, while the other is of large size and is conducive to transform the cloud droplets to raindrops. The model is analyzed using stability theory of differential equations and computer simulation. The model analysis shows that due to the introduction of conducive aerosol particles in the regional atmosphere, the rainfall increases as compared to the case when no aerosols are introduced in the atmosphere of the region under consideration. The computer simulation confirms the analytical results.     

Impact microcrater morphology on Australasian microtektites

Abstract— Scanning electron microscopy of 137 Australasian microtektites and fragments from 4 sediment cores in the Central Indian Ocean reveals more than 2000 impact‐generated features in the size range of 0.3 to 600 μm. Three distinct impact types are recognized: destructive, erosive, and accretionery. A large variation in impact energy is seen in terms of catastrophic destruction demonstrated by fragmented microtektites through erosive impacts comprising glass‐lined pit craters, stylus pit craters, pitless craters, and a small number of accretionery features as well. The size range of observed microtektites is from 180 to 2320 μm, and not only are the smaller microtektites seen to have the largest number of impacts, but most of these impacts are also of the erosive category, indicating that target temperature is an important factor for retaining impact‐generated features. Further, microcratering due to collisions in impact‐generated plumes seems to exist on a larger and more violent scale than previously known. Although the microcraters are produced in a terrestrially generated impact plume, they resemble lunar microcraters in many ways: 1) the size range of impacts and crater morphology variation with increasing size; 2) dominant crater number densities in μm and sub‐μm sizes. Therefore, tektite‐producing impacts can lead to the generation of microcraters that mimic those found on lunar surface materials, and for the lunar rocks to qualify as reliable cosmic dust flux detectors, their tumbling histories and lunar surface orientations have to be known precisely.     

Impact microcraters on an Australasian microtektite

Abstract— Microcraters attributable to impact have been discovered on an Australasian microtektite from a core in the Central Indian Basin. The craters resemble lunar microcraters and those generated during impact experiments. The largest crater here, which has a welded promontory, is unique. The projectiles that produced the impacts defined varying trajectories and velocities, ranging from hypervelocity to low velocity (a few 10 m/s). The impacts took place while the microtektite was in flight at an elevated target temperature. This is the first observation of the microimpact phenomenon on a microtektite.     

Two layers of Australasian impact ejecta in the Indian Ocean?

Abstract— Only 2 Australasian tektites have been found in the Indian Ocean, and both are associated with surficial sediments. We collected cores from both locations where the tektites have been reported. The microtektites in these cores (and both the tektites, as reported earlier) have chemical compositions within the compositional range previously reported for Australasian tektites and microtektites. In both locations, while the tektites are occurring at the sediment/water interface, the microtektites are found buried in older horizons beneath the seafloor at stratigraphic levels, conforming to the radiometric age of the strewn field. Thus, at first glance, there appear to be 2 layers of Australasian impact ejecta in the Indian Ocean. However, the manganese nodules are associated with the tektites which, although millions of years old, are invariably resting on recent sediments. Therefore, the mechanism that retains nodules at the seafloor also seems to be operative on the tektites, thus leading to this apparent “age paradox” of tektite/microtektite distribution in the Indian Ocean, although they both belong to the same impact event.     

The structure of the equatorial mesosphere at Thumba

The structure of the equatorial mesosphere is being investigated at Thumba by rocket borne ultraviolet absorption photometry as well as by the meteorological M-100 rocket launching programme. Whereas the meteorological M-100 rocket luanching programme has been regular, the UV absorption studies have been few in number and sporadic in nature. In this paper an attempt is made to consolidate the results so far obtained from both these investigations.     

Some geoelectrical investigations for potential groundwater zones in part of Azamgarh area of U.P.

Summary The results of some electrical sounding measurements have been used for defining potential groundwater zones in part of Azamgarh district of Uttar Pradesh, India. The area covered is a part of gangetic alluvial tract. Aquifers consist of lenticular sand masses distributed within the alluvium. The ideal geoelectrical conditions, generally desired for the interpretation of resistivity curves, lack in the area. Among the number of layers encountered in lithologs, only a few are delineated by quantitative interpretation of the sounding data. A study of the total transverse resistance and longitudinal conductance for a particular depth of the alluvial column has helped in defining potential groundwater zones.