Implication of the Middle Jurassic pholadomyoids of Kachchh in the palaeobiogeography of the Middle East and South Asia: A review

The Kachchh basin is known world over for its rich occurrence of the Middle to Late Jurassic mollusks. The Middle Jurassic sediments in Kachchh range in age from Bajocian (possibly Aalenian) to Callovian. Amongst the Middle Jurassic benthic communities of Kachchh, the pholadomyoid bivalves are one of the dominant groups in both diversity and number. These are represented by 13 genera and 30 constituent species. Distribution of these bivalves was much affected by the evolutionary history of the basin which has been created due to inundation by Tethys sea owing to the opening of Arabian sea sometime in Middle Jurassic. By and large these fauna are typical of the southern Hemisphere and belonged to east African biochore of the Tethyan realm or to the so called Ethiopian faunal province. Analyzing the (palaeo-) autecological behavior of the studied pholadomyoid bivalves and their distribution pattern, an attempt has been made to ascertain the usefulness of these pholadomyoids in evaluating the Middle Jurassic paleobiogeography.     

Models of rapidly rotating white dwarfs

Numerical solutions of the structural equations for rapidly rotating white dwarfs are tabulated for values of the central density parametery ^–2 _o ranging from 0.0001 to 0.80. The physical parameters of white dwarfs rotating at the break-up velocity are also tabulated. Further, the massradius relations for both the equatorial and the polar radii are derived. These two relations are found to differ from other recent theoretical calculations by less than 10 and 4%, respectively. The use of uniformly rotating white dwarf models to account for the observational data on Sirius B is discussed. It is concluded that Sirius B may be rotating rapidly and near its break-up velocity. Further it is suggested that the radius and Einstein red shift for this star are 0.01135 R and 59 km/sec.     

The structure of rapidly rotating relaxed globular clusters

A model of rapidly rotating globular clusters is constructed assuming uniform angular velocity and a truncated Maxwellian distribution in the stellar velocities. Since the first-order theory developed by Woolley and Dickens becomes inaccurate for rapid rotation, a small-mass envelope is fitted to their models by the method of Monaghan and Roxburgh. A comparison is made of the critical values derived by the two methods.     

Locating oceanic Tuna resources in the Eastern Arabian sea using remote sensing

Tuna fishery resources are currently under exploited. The resource potential of tunas in the Indian Exclusive Economic Zone (EEZ) beyond 50 m depths is around 2.09 lakh tonnes as estimated by Fishery Survey of India. The distribution and availability of the tuna are governed by environmental factors like temperature, thermocline depth, availability of prey, visibility etc. Remote sensing provides synoptic information on productivity in terms of chlorophyll and Sea Surface Temperature (SST). In the present paper, satellite remote sensing data from Indian Remote Sensing Satellite IRS- P4 Ocean Colour Monitor (OCM) sensor for chlorophyll-a and diffuse attenuation coefficient (K) and National Oceanic and Atmospheric Administration (NOAA) - Advanced Very High Resolution Radiometer (AVHRR) sensor data for sea surface temperature were analysed and correlated within situ catch data of oceanic tunas, Skipjack(Katsuwonus pelamis) and Yellowfin tuna(Thunnus albacares), off Maharashtra coast. Higher catches were found to be associated with moderate to good primary productivity and in the vicinity of thermal fronts. Relationship between Hooking rate and SST has shown that SST of 28–30°C range is optimum for skipjack and 28–31°C for yellowfin tuna. Besides satellite derived chlorophyll and SST for identification of potential tuna fishing zones, role of diffuse attenuation coefficient (K) for visibility factor is also discussed.     

Impact of tsunami on aquaculture farms along the nagapattinam coast zone,Tamil Nadu,India

The tsunami waves triggered by underwater earthquake with a focal depth of 30 km near the Sumatra Island distressed the entire coast of Tamil Nadu. The worst affected coastal region is Nagapattinam, particularly from Nagoore to Vailankanni. The impact of tsunami had multidimensional effect, killing most of the fishermen communities, devastating the coastal huts and damaging the coastal aquaculture resources. The present study has been carried out to find the impact of tsunami on the aquaculture small farmland owners along the coast using pre (December 18, 2004) and post January 6, 2005) IRS P6 data. The study includes the extent of damage caused to the farms by saltwater intrusion; sand inundation, total destruction of farms. The results indicate that, there have been incredible damage caused to the farmers beyond recovery in short span of time.     

Tissemouminites: A new group of primitive achondrites spanning the transition between acapulcoites and winonaites

The Northwest Africa (NWA) 090 meteorite, initially classified as an acapulcoite, presents petrological, chemical, and isotopic characteristics comparable to a group of seven primitive winonaites: Dhofar 1222, NWA 725, NWA 1052, NWA 1054, NWA 1058, NWA 1463, and NWA 8614. Five of these samples were previously classified as acapulcoites or ungrouped achondrites before being reclassified as winonaites based on their oxygen isotopic compositions. These misclassifications are indicative of the particular compositional nature of these primitive achondrites. All contain relict chondrules and a lower closure temperature of metamorphism of 820 ± 20 °C compared to other typical winonaites, as well as mineral elemental compositions similar to those of acapulcoites. The oxygen isotopic signature of these samples, δ¹⁷O of 1.18 ± 0.17‰, δ¹⁸O of 3.18 ± 0.30‰, and Δ¹⁷O of −0.47 ± 0.02, is in fact resolvable from both acapulcoites and winonaites. We investigate the relationship between these eight primitive achondrites, typical winonaites, and acapulcoites, to redefine petrological, mineralogical, and geochemical criteria of primitive achondrite classification. Distinguishing between winonaites, acapulcoites, and this group of eight primitive achondrites can be unambiguously done using a combination of several mineralogical and chemical criteria. A combination of olivine fayalite content and FeO/MnO ratio, as well as plagioclase potassium content allow us to separate these three groups without the absolute necessity of oxygen isotope analyses. NWA 090 as well as the other seven primitive achondrites, although related to winonaites, are most likely derived from a parent body distinct from winonaites and acapulcoites–lodranites, and define a new group of primitive achondrites that can be referred to as tissemouminites.     

Environmental geochemistry and quality assessment of mine water of Jharia coalfield,India

A long mining history and unscientific exploitation of Jharia coalfield caused many environmental problems including water resource depletion and contamination. A geochemical study of mine water in the Jharia coalfield has been undertaken to assess its quality and suitability for domestic, industrial and irrigation uses. For this purpose, 92 mine water samples collected from different mining areas of Jharia coalfield were analysed for pH, electrical conductivity (EC), major cations (Ca²⁺, Mg²⁺, Na⁺, K⁺), anions (F⁻, Cl⁻, HCO₃ ⁻, SO₄ ²⁻, NO₃ ⁻), dissolved silica (H₄SiO₄) and trace metals. The pH of the analysed mine water samples varied from 6.2 to 8.6, indicating mildly acidic to alkaline nature. Concentration of TDS varied from 437 to 1,593 mg L⁻¹ and spatial differences in TDS values reflect the variation in lithology, surface activities and hydrological regime prevailing in the region. SO₄ ²⁻ and HCO₃ ⁻ are dominant in the anion and Mg²⁺ and Ca²⁺ in the cation chemistry of mine water. High concentrations of SO₄ ²⁻ in the mine water of the area are attributed to the oxidative weathering of pyrites. Ca–Mg–SO₄ and Ca–Mg–HCO₃ are the dominant hydrochemical facies. The drinking water quality assessment indicates that number of mine water samples have high TDS, total hardness and SO₄ ²⁻ concentrations and needs treatment before its utilization. Concentrations of some trace metals (Fe, Mn, Ni, Pb) were also found to be above the desirable levels recommended for drinking water. The mine water is good to permissible quality and suitable for irrigation in most cases. However, higher salinity, residual sodium carbonate and Mg-ratio restrict its suitability for irrigation at some sites.     

Feasibility of Coupled Pattern Reconstruction Technique in the Detection of Internal Waves

A key problem of contemporary static and kinematic positioning is the problem of transformation of conformai coordinates of universal Mercator projection (UMP) type from a local datum (regional, national) to a global datum, for instance, the World Geodetic System 1984 (WGS 84) with reference to Boyle (1987). Such a problem is met if we use WGS 84 GPS‐derived ellipsoidal coordinates of a point for localization in a local chart of UMP type. In this article we derive and test the equations of a curvilinear datum transformation of ellipsoidal GPS coordinates in a global datum to conformai coordinates of UMP type in a local datum. The curvilinear datum transformation includes three parameters for translation, three parameters for rotation, one scale parameter, and two form parameters which account for a change in the semimajor axis and in the relative eccentricity of the reference ellipsoid.