Evaluation of Organic Matter,Hydrocarbon Source,and Depositional Environment of Onshore Warkalli Sedimentary Sequence from Kerala-Konkan Basin,South India

Multidisciplinary analysis of the carbonaceous sediments of Warkalli Formation (Mio-Pliocene) from the Warkalli cliff section has been done to assess the source of organic matter, palaeodepositional settings and the hydrocarbon potential. The n-alkane distribution from n-C₁₂ to n-C₃₃ along with bimodal distribution indicates significant organic matter contribution from microbial activity and higher plants. The contribution from angiosperm source vegetation is indicated by the oleanane type of triterpenoids. The hopanes distribution indicates the immature stage of the organic matter, which is in agreement with the T_max (av. 401 °C) and huminite reflectance (av. 0.28% R_r) values. The total organic carbon (TOC) contents vary between 0.8 and 6.72 wt. % in the studied sediments. Hydrogen index and oxygen index values range from 16 to106 mg HC/g TOC, and 113 to 344 mg CO₂/g TOC, respectively. The maceral content is low, being dominated by the detrohuminite submaceral and the mineral matter accounts for 68 to 77% of the total composition. The phytoclast group (63–87%) is dominant with subordinate amorphous organic matter (4–35%). The study shows that the sediments were deposited in a marginal suboxic basin with intermittent variations. All the parameters unequivocally suggest that the studied sequence holds the potential to generate gaseous hydrocarbons.     

Controls on sedimentation in distal margin palaeovalleys in the Early Tertiary Alpine foreland basin, south-eastern France

The influence of palaeodrainage characteristics, palaeogeography and tectonic setting are rarely considered as controls on stratigraphic organization in palaeovalley or incised valley systems. This study is an examination of the influence of source region vs. downstream base level controls on the sedimentary architecture of a set of bedrock-confined palaeovalleys developed along the distal margin of the Alpine foreland basin in south-eastern France. Three distinct facies associations are observed within the palaeovalley fills. Fluvial facies association A is mainly dominated by poorly sorted, highly disorganized, clast-to-matrix-supported cobble-to-boulder conglomerates that are interpreted as streamflood deposits. Facies association B comprises mainly yellow siltstones and is interpreted as recording deposition in an estuarine basin environment. Estuarine marine facies association C comprises interstratified estuarine siltstones and clean, well-sorted washover sandstones. The sedimentary characteristics of the valley fill successions are related to the proximity of depositional sites to sediment source areas. Palaeovalleys located proximal to structurally controlled basement palaeohighs are entirely dominated by coarse fluvial streamflood deposits. In contrast, distal palaeovalley segments, which are located several kilometres downstream, contain successions showing upward transition from coarse fluvial facies into estuarine central basin fines, and finally into estuarine-marginal marine facies. Facies distributions suggest that the fluvial deposits form wedge-shaped, downstream-thinning sediment bodies, whereas the estuarine deposits form an upstream-thinning wedge. The vertical stacking of fluvial to estuarine to marginal marine depositional environments records the fluvial aggradation and subsequent transgression of relatively small bedrock-confined river valleys, which drained a rugged, upland terrain. Facies geometries suggest that a fluvial sediment wedge initially prograded downvalley, in response to high bed load sediment yields. Subsequently, palaeovalleys became drowned during the passage of a marine transgression, with the establishment of estuarine conditions. Initial fluvial aggradation and subsequent marine flooding of the palaeovalleys is a consequence of the interaction of high local rates of sediment supply and relative sea-level rise driven by flexural subsidence of the basin.     

The potential contribution of wildlife sanctuary to forest conservation: A case study from binsar wildlife sanctuary

Forest vegetation of a protected area(Binsar Wildlife Sanctuary) in Kumaun region(west Himalaya) was analysed for structure,composition and representativeness across three different altitudinal belts,lower(1,600-1,800 m a.s.l.),middle(1,900-2,100 m a.s.l.) and upper(2,200-2,400 m a.s.l.) during 2009-2011 using standard phytosociological methods.Four aspects(east,west,north and south) in each altitudinal belt were chosen for sampling to depict maximum representation of vegetation in the sanctuary.Population structure and regeneration behaviour was analysed seasonally for two years to show the establishment and growth of tree species.A total of 147 plant species were recorded from the entire region of which 27 tree species were selected for detailed study.Highest number was recorded at upper(18 species),and lowest at lower altitudinal belt(15 species).The relative proportion of species richness showed higher contribution of tree layer at each altitudinal belt.The population structure,based on the number of individuals,revealed a greater proportion of seedling layer at each altitudinal belt.The relative proportion of seedlings increases significantly along altitudinal belts(p<0.05) while opposite trends were observed in sapling and tree layers.The density of sapling and seedling species varied non-significantly across seasons(p>0.05).The density values decreased in summer and increased during rainy season.As far as the regeneration status is concerned,middle and upper altitudinal belts showed maximum number of species with fair regeneration as compared to lower altitudinal belt.Overall density diameter distribution of tree species showed highest species density and richness in the smallest girth class and decreased in the succeeding girth classes.This study suggests that patterns of regeneration behaviour would determine future structural and compositional changes in the forest communities.It is suggested that the compositional changes vis-à-vis role of ‘New’ and ‘Not regenerating’ species need priority attention while initiating conservation activities in the sanctuary.This study calls for exploring other less explored Wildlife Sanctuaries in the Himalaya and across the world,to achieve overall biodiversity status in these protected areas and thus to justify their role in conserving biodiversity in the region.     

ORDERED PEAK STATISTICS THROUGH DIGITAL SIMULATION

A detailed knowledge of the seismic response time history in the form of the first, second, third, … largest peak amplitudes is useful to understand the progressive damage in a structure. This information is however not available from the conventionally used response spectra. This paper provides a formulation of the statistics of these higher order peaks by proposing a digitally simulated joint density function for the peaks in a stationary, Gaussian process. A digital experimentation has been done by generating an ensemble of the single-degree-of-freedom oscillator response to several artificial accelerograms, and the corresponding ordered peak distributions have been found to be in close agreement with the predictions based on the formulation in this paper. The peak factors based on the proposed formulation have also been compared with those from the existing formulations based on the Markov theory and on the assumption of peak independence. It has been found that whereas the peak factors from the proposed and Markovian formulations are compatible, the assumption of independence may give reasonable estimates only for the first few orders of peaks.     

PROPAGATION OF TORSIONAL SURFACE WAVES IN A HOMOGENEOUS SUBSTRATUM OVER A HETEROGENEOUS HALF-SPACE

The paper discusses the propagation of torsional surface wave in a homogeneous substratum over a half-space with linearly varying rigidity and density. The study reveals that under assumed conditions, a torsional surface wave propagates in the medium. The velocities of torsional surface waves have been calculated numerically and are presented in a number of graphs. It is also observed that for a stratum over a homogeneous half-space, the velocity of torsional surface waves coincides with that of Love waves. For a non-homogeneous half-space it is observed that the velocity of torsional surface waves is always higher than that of Love waves propagated in a homogeneous layer over a homogeneous half-space. An attempt is also made to assess the possible propagation of torsional surface waves in a half-space with linearly varying rigidity and density, lacking a superficial layer. It is concluded that such a half-space allows two solutions for torsional waves while a homogeneous half-space has one.     

DIKE FORMATION WITH SUBMERGED VANE

1 INTRODUCTION Increasing capital costs, emerging environmental concerns and rising maintenance expenses of conventional river training works around the world have led to the development of submerged vanes in practice. Submerged vanes are being favoured f…     

Influences of Freshwater from Major Rivers on Global Ocean Circulation and Temperatures in the MIT Ocean General Circulation Model

Responses of global ocean circulation and temperature to freshwater runoff from major rivers were studied by blocking regional runoff in the global ocean general circulation model(OGCM)developed at the Massachusetts Institute of Technology.Runoff into the tropical Atlantic,the western North Pacific,and the Bay of Bengal and northern Arabian Sea were selectively blocked.The blocking of river runoff first resulted in a salinity increase near the river mouths(2 practical salinity units).The saltier and,therefore,denser water was then transported to higher latitudes in the North Atlantic,North Pacific,and southern Indian Ocean by the mean currents.The subsequent density contrasts between northern and southern hemispheric oceans resulted in changes in major ocean currents.These anomalous ocean currents lead to significant temperature changes(1°C-2°C)by the resulting anomalous heat transports.The current and temperature anomalies created by the blocked river runoff propagated from one ocean basin to others via coastal and equatorial Kelvin waves.This study suggests that river runoff may be playing an important role in oceanic salinity,temperature,and circulations;and that partially or fully blocking major rivers to divert freshwater for societal purposes might significantly change ocean salinity,circulations,temperature,and atmospheric climate.Further studies are necessary to assess the role of river runoff in the coupled atmosphere-ocean system.     

Changes in abundance and nature of microimpact craters on the surfaces of Australasian microtektites with distance from the proposed source crater location

Abstract– Over 4600 Australasian microtektites from 11 sediment cores along an N–S transect in the Central Indian Ocean have been investigated optically for microimpact features on their surfaces. Detailed scanning electron microscope examination of 68 microtektites along this transect shows 4091 such features. These samples are located between approximate distances of 3900–5000 km from the suggested impact site in Indochina and therefore constitute distal ejecta. The morphology of the microimpacts seems to show distinct variations with distance from the source crater. The total number of microcraters on each microtektite decreases drastically from North to South indicating systematic decrease in the spatial density of the ejecta, and decrease in collisional activity between microtektites with distance from the proposed source crater location. Closer to the proposed source crater location, the microcraters are predominantly small (few μm), pit bearing with radial and concentric cracks, suggestive of violent interparticle collisions. The scenario is reverse farther from the source crater with smaller numbers of impacted microtektites due to increased dispersion of the ejecta and the microcraters are large and shallow, implying gentle collisions with larger particles. These observations provide systematic ground truth for the processes that take place as the ejecta of a large oblique impact which generated the Australasian tektite strewn field is emplaced. The microimpacts appear to take place during the descent of the ejecta and their intensity and number density decrease as a function of the spatial density of the ejecta at any given place and with distance from the source region. These features could help understand processes that take place during ejecta emplacement on planets with substantial atmosphere such as Mars and Venus.     

Bacterial response to contrasting sediment geochemistry in the Central Indian Basin

In order to investigate whether geochemical, physiographic and lithological differences in two end‐member sedimentary settings could evoke varied microbe–sediment interactions, two 25 cm long sediment cores from contrasting regions in the Central Indian Basin have been examined. Site TVBC 26 in the northern siliceous realm (10°S, 75·5°E) is organic‐C rich with 0·3 ± 0·09% total organic carbon. Site TVBC 08 in the southern pelagic red clay realm (16°S, 75·5°E), located on the flank of a seamount in a mid‐plate volcanic area with hydrothermal alterations of recent origin, is organic‐C poor (0·1 ± 0·07%). Significantly higher bacterial viability under anaerobic conditions, generally lower microbial carbon uptake and higher numbers of aerobic sulphur oxidizers at the mottled zones, characterize core TVBC 26. In the carbon‐poor environment of core TVBC 08, a doubling of the ¹⁴C uptake, a 250 times increase in the number of autotrophic nitrifiers, a four‐fold lowering in the number of aerobic sulphur oxidizers and a higher order of denitrifiers exists when compared with core TVBC 26; this suggests the prevalence of a potentially autotrophic microbial community in core TVBC 08 in response to hydrothermal activity. Microbial activity at the northern TVBC 26 is predominantly heterotrophic with enhanced chemosynthetic activity restricted to tan‐green mottled zones. The southern TVBC 08 is autotrophic with increased heterotrophic activity in the deepest layers. Notably, the bacterial activity is generally dependent on the surface productivity in TVBC 26, the carbon‐rich core, and mostly independent in TVBC 08, the carbon‐poor, hydrothermally influenced core. The northern sediment is more organic sink‐controlled and the southern sediment is more hydrothermal source‐controlled. Hydrothermal activity and associated rock alteration processes may be more relevant than organic matter delivery in these deep‐sea sediments. Thus, this study highlights the relative importance of hydrothermal activity versus organic delivery in evoking different microbial responses in the Central Indian Basin sediments.