Chelonodontops bengalensis (Tetraodontiformes: Tetraodontidae): A New Species of Puffer Fish from the Northern Bay of Bengal Based on Morphology and DNA Barcode

Ocean Science Journal - The new puffer fish species Chelonodontops bengalensis (Pisces: Tetraodontidae) is described from two specimens collected on the southwest coast of the Bay of Bengal,...     

Plant species diversity along an altitudinal gradient of Bhabha Valley in western Himalaya

The present study highlights the rich species diversity of higher plants in the Bhabha Valley of western Himalaya in India. The analysis of species diversity revealed that a total of 313 species of higher plants inhabit the valley with a characteristic of moist alpine shrub vegetation. The herbaceous life forms dominate and increase with increasing altitude. The major representations are from the families Asteraceae, Rosaceae, Lamiaceae and Poaceae, suggesting thereby the alpine meadow nature of the study area. The effect of altitude on species diversity displays a hump-shaped curve which may be attributed to increase in habitat diversity at the median ranges and relatively less habitat diversity at higher altitudes. The anthropogenic pressure at lower altitudes results in low plant diversity towards the bottom of the valley with most of the species being exotic in nature. Though the plant diversity is less at higher altitudinal ranges, the uniqueness is relatively high with high species replacement rates. More than 90 % of variability in the species diversity could be explained using appropriate quantitative and statistical analysis along the altitudinal gradient. The valley harbours 18 threatened and 41 endemic species, most of which occur at higher altitudinal gradients due to habitat specificity.     

Triggering processes of deep-seated gravitational slope deformation (DSGSD) in an un-glaciated area of the Cavargna Valley (Central Southern Alps) during the Middle Holocene

Triggering mechanisms and causative processes of deep-seated gravitational slope deformations (DSGSD) in Alpine and high mountain areas include, among others, post-glacial de-buttressing, earthquake-induced ground shaking, or co-seismic surface faulting. Distinguishing between climatic or tectonically driven factors is challenging since faults and fracture systems can play both an active and/or passive role in the process initiation. We applied an integrated approach, including morpho-structural analysis, geologic field survey, a paleoseismological approach applied to trenching, radiocarbon dating and detailed sedimentological analysis, to a DSGSD located in the Cavargna Valley (N Italy), an area that was never occupied by extensive ice tongues in the Upper Pleistocene and Holocene. We were able to document at least two phases of movement from the Middle Holocene onwards and related triggering factors. Thanks to the comparison with dated lacustrine turbidites in the Alpine Lakes, we argue a seismic triggering for the landslide onset, with a possible source located in southern Switzerland, close to the Insubric Line. The later evolution of the landslide was instead driven by climatic predisposing conditions (humid and cold), instead, corresponding to a phase of enhanced slope instability.

     

Evidence for heterogeneous enriched shergottite mantle sources in Mars from olivine-hosted melt inclusions in Larkman Nunatak 06319

Larkman Nunatak (LAR) 06319 is an olivine-phyric shergottite whose olivine crystals contain abundant crystallized melt inclusions. In this study, three types of melt inclusion were distinguished, based on their occurrence and the composition of their olivine host: Type-I inclusions occur in phenocryst cores (Fo_77-73); Type-II inclusions occur in phenocryst mantles (Fo_71-66); Type-III inclusions occur in phenocryst rims (Fo_61-51) and within groundmass olivine. The sizes of the melt inclusions decrease significantly from Type-I (∼150-250 μm diameter) to Type-II (∼100 μm diameter) to Type-III (∼25-75 μm diameter). Present bulk compositions (PBC) of the crystallized melt inclusions were calculated for each of the three melt inclusion types based on average modal abundances and analyzed compositions of constituent phases. Primary trapped liquid compositions were then reconstructed by addition of olivine and adjustment of the Fe/Mg ratio to equilibrium with the host olivine (to account for crystallization of wall olivine and the effects of Fe/Mg re-equilibration). The present bulk composition of Type-I inclusions (PBC1) plots on a tie-line that passes through olivine and the LAR 06319 whole-rock composition. The parent magma composition can be reconstructed by addition of 29 mol% olivine to PBC1, and adjustment of Fe/Mg for equilibrium with olivine of Fo₇₇ composition. The resulting parent magma composition has a predicted crystallization sequence that is consistent with that determined from petrographic observations, and differs significantly from the whole-rock only in an accumulated olivine component (∼10 wt%). This is consistent with a calculation indicating that ∼10 wt% magnesian (Fo_77-73) olivine must be subtracted from the whole-rock to yield a melt in equilibrium with Fo₇₇. Thus, two independent estimates indicate that LAR 06319 contains ∼10 wt% cumulate olivine.The rare earth element (REE) patterns of Type-I melt inclusions are similar to that of the LAR 06319 whole-rock. The REE patterns of Type-II and Type-III melt inclusions are also broadly parallel to that of the whole-rock, but at higher absolute abundances. These results are consistent with an LAR 06319 parent magma that crystallized as a closed-system, with its incompatible-element enrichment being inherited from its mantle source region. However, fractional crystallization of the reconstructed LAR 06319 parent magma cannot reproduce the major and trace element characteristics of all enriched basaltic shergottites, indicating local-to-large scale major- and trace-element variations in the mantle source of enriched shergottites. Therefore, LAR 06319 cannot be parental to the enriched basaltic shergottites.     

First report of eudialyte occurrence from the Sushina hill region,Purulia district,West Bengal

Eudialyte is a group of hydrated silicate minerals essentially consisting of Na and Zr with a very complex crystal structure, and generally associated with alkaline rocks. The complexity of the eudialyte structure can be understood from the fact that Na alone exist in five distinct sites and extensive solid solubility can occur in almost all cation sites, sometimes one element occupying multiple sites to the extent of exclusion of other elements. Structurally, eudialyte can be represented as Na₁₅[M ₁ ]₆[M 2]₃Zr₃[M ₃ ](Si₂₅O₇₃)(O,OH,H₂O)₃X₂ (Johnsen and Grice, 1999), where M ₁ and M ₂ sites are occupied by Ca, Mn and Fe, M ₃ by Nb and X by OH, Cl and F. In addition, cations like Al, Hf, W, Ta, Sr, Ba and various REEs get incorporated into the eudialyte structure by substitution, and additional site vacancies even may develop in order to maintain electrical neutrality. Eudialyte, approximately of the composition Na₉Ca₈Mn₃Nb(Zr,Ce)₃Si₂₅O₇₃(OH)₂, has hydrothermally replaced albite in the nepheline syenite gneiss exposed south of the Sushina hill of Purulia district, West Bengal. The eudialyte contains ≈2.25 atom% Zr and 0.75 atom% Nb. In addition to eudialyte in nepheline syenite, an unknown Na-Zr silicate (NZS) has also replaced the albite crystals. The NZS contains ≈ 7 atom% Zr with a possible empirical formula of Na₁₂Zr₁₁Si₃₆O₉₅(OH)₁₀. Surface exposures of these rocks are limited at Sushina hill, yet a detailed and systematic investigation on this enigmatic rock is warranted for they may turn out to be a resource for Zr.     

History of faulting and magmatism in the Galilee (Israel) and across the Levant continental margin inferred from potential field data

The Galilee study area, northern Israel, is at present an uplifted, steep continental margin that formed mainly during the Jurassic and has a large positive isostatic anomaly. Since the Jurassic, it was modified by several tectonomagmatic events, which this study attempts to define and classify by updating, reprocessing and reinterpreting gravity, aeromagnetic and geological data. The prominent Rehovot-Carmel N–S positive reduced-to-pole (RTP) magnetic anomaly caused by the Gevim Volcanics, as well as the coexisting Helez-Gaash high Bouguer gravity and the Pleshet low Bouguer gravity, represent the deep (>5 km) Permo-Triassic dominant horst and graben structure of Israel. The Jonah Ridge and Beirut high SW–NE RTP magnetic anomalies in the Levant basin delineate the Levant continental edge that is marked by a deeply buried horst covered by a Late Cretaceous volcanic complex. The Asher and Devora Jurassic volcanics appear to be responcible for the Atlit and Galilee negative magnetic anomalies and for significant negative gravity anomalies which became clear after removing gravity effect of the upper (post-Turonian) light density sediments from the observed gravity. The volcanics extend along a SW–NE belt parallel to the strike of the Moho. It is suggested here that the Carmel-Gilboa fault propagated during the Late Cretaceous from the Levant basin across the Galilee area southeastward to form the Azraq-Sirhan graben in Jordan. As such, it forms a right-step, en echelon, dextral strike-slip fault with associated tectonic basins of various shapes. During the Oligocene and before formation of the Dead Sea transform (DST), the reactivation of the Azraq-Sirhan graben was accompanied by tectonic driven rift propagation in the opposite direction, from Azraq-Sirhan to northwest. It dispersed into many faults and terminated ∼10 km west of the present DST. During the Miocene it propagated in the same direction and includes internal volcanic activity. The numerous Miocene-Pliocene volcanic centers on the margins of the DST indicate that the preferred pathway for magmas at that time was not within the deep basins of the DST.     

Effect of Compressive Load on Uplift Capacity of Cast-Insitu Bored Piles

Field tests were conducted to study the effect of compressive loading on the uplift capacity of single piles embedded in silty sand. The test program consists of four instrumented cast in situ axial pile load tests in compression, pure tension and tension with 25 and 50% of compressive load of ultimate capacity in compression. The experimental results indicate that the net ultimate uplift capacity of single pile decreases with increase in compressive load. The shaft friction is non linear in nature. It observed that as the compressive load increases the shaft friction along the length of pile decreases.     

GPS scintillation studies in the arctic region during the first winter-phase 2008 Indian Arctic Expedition

We present the results of scintillation studies based on the data obtained during the first winter-phase Indian Arctic Expedition in March 2008 at the Indian Himadri Station, Ny-Ålesund (78.9°N, 11.9°E), in the vicinity of the daytime cusp and under the nightside polar cap. A global-positioning-system ionospheric scintillation and TEC monitor (GISTM) receiver (model GSV4004A) was used to record scintillations and the total electron content (TEC). The polar ionosphere is more sensitive to phase than to amplitude scintillations. Occurrence of amplitude scintillation is confined to well-defined regions, while phase scintillation shows a strong characterization both in magnetic latitude and magnetic local time. Occurrence of amplitude and phase scintillation increases during disturbed compared with quiet days. During disturbed days, the phase-scintillation region is displaced towards lower latitudes, following the auroral oval. The observed noon peak in scintillation occurrence may indicate that the irregularities that generate scintillation are caused by precipitation in the daytime cusp/cleft region. A significant enhancement of the TEC and the rate of change of the TEC index (ROTI) signified transits of polar-cap patches across different satellite trajectories during geomagnetic storms. We found that patches are most likely to occur when IMF Bz is southward and/or K_p > 4. Loss of signal lock was more for the L2 signal than for L1, and shows a maximum in the morning sector. Positional errors tend to increase during disturbed conditions.     

Palaeoecological implications of corallinacean red algae and halimedacean green algae from the prang formation of south shillong plateau, meghalaya

The southwestern part of south Shillong plateau (Meghalaya, N-E India), designated as Sylhet Limestone Group is sub-divided into three lithounits i.e., Lakadong, Umlatdoh and Prang formations in ascending order. The Prang Formation is the youngest lithostratigraphic unit of the Sylhet Limestone Group and has been dated as Middle to early Upper Eocene based on the benthic foraminifera studies. Thin section analysis of carbonate rocks from Prang Formation, exposed in the Bholaganj limestone quarry yielded a rich assemblage of calcareous algae. The coralline algal assemblage comprises both non-geniculate and geniculate forms. The green algae are represented by species of Halimeda belonging to the family Halimedaceae. Palaeoecological interpretation based on diversity, growth-form analysis and taphonomic aspects of the algal assemblage indicate that in all probabilities the deposition of Prang Formation occurred in shallow, warm, shelf environment of normal salinity within the transgressive phase.