Organic geochemistry and source rock potential assessment of Late Paleocene Patala Formation in Margalla Hill Range,North Pakistan

Black shales of the Paleocene Patala Formation are proven source rocks for conventional hydrocarbons in southern Potwar Basin of Pakistan and are assumed to be effective source rocks towards north in the Margalla Hill Range of Pakistan. In this regard, the current study focuses on source rock geochemistry of the Paleocene Patala Formation to assess its source rock potential, organic matter types and thermal maturity levels in the Mar-galla Hill Range of North Pakistan. Source rock generative potential, kerogen types and thermal maturation of the analysed rock samples were unraveled by using Rock-Eval pyrolysis Tmax, TOC (total organic carbon) and vitrinite reflectance ( R0 ) analyses. TOC analysis coupled with S2 yield revealed poor to fair source rock quality encountered within the formation. The pyrolysis Tmax vs Hydrogen Index ( HI) , showed mostly Type Ⅲ kerogen dominated by thermally immature to mature organic matter. The HI and genetic potential is low and revealed poor hydrocarbon generation potential of the formation. The S1 vs TOC plots confirm the indigenous nature of the hydrocarbons hosted by Patala Formation. The vitrinite reflectance outcomes indicated immature to mature source rock beds lying in dry gas zone. The HI and OI signatures and abundance of Type Ⅲ kerogen are indica-ting dominance of terrestrial organic matter within the formation. Overall, the investigated Patala Formation ex-posed at the studied section of Margalla Hill Range, Pakistan acts as a poor source rock unit for liquid hydrocar-bon generation but holds prospects for dry gas generation in the study area.     

On some fabaceous fruits from the Siwalik sediments (Middle Miocene-Lower Pleistocene) of Eastern Himalaya

Four legume fruits (Fabaceae) from the Siwalik sediments (middle Miocene to lower Pleistocene) of Darjeeling and Arunachal Pradesh of Eastern Himalaya are described here. One fossil fruit, Dalbergia prelatifolia sp. nov., is recovered from the lower part of the Siwalik succession (Gish Clay Formation of Sevok Group; middle to upper Miocene) of Darjeeling foothills. Mastertia neoassamica sp. nov. and Acacia miocatechuoides sp. nov. are collected from the lower part of the Siwalik succession (Dafla Formation; middle Miocene to upper Miocene), while Pongamia kathgodamensis Prasad is recovered from the upper part of the Siwalik succession (Kimin Formation; upper Pliocenelower Pleistocene) of Arunachal sub Himalaya. Their presence indicates a warm and humid tropical environment in the region during the Siwalik sedimentation.     

Earthquake source characteristics along the arcuate Himalayan belt: Geodynamic implications

The occurrences of moderate to large magnitude earthquakes and associated subsurface geological processes were critically examined in the backdrop of Indian plate obliquity, stress obliquity, topography, and the late Tertiary regional tectonics for understanding the evolving dynamics and kinematics in the central part of the Himalayas. The higher topographic areas are likely associated with the zones of depressions, and the lower topographic areas are found around the ridges located in the frontal part of the orogen. A positive correlation between plate and stress obliquities is established for this diffuse plate boundary. We propose that the zone of sharp bending of the descending Indian lithosphere is the nodal area of major stress accumulation which is released occasionally in form of earthquakes. The lateral geometry of the Himalayas shows clusters of seismicity at an angle of ～20^° from the centre part of the arc. Such spatial distribution is interpreted in terms of compression across the arc and extension parallel to the arc. This biaxial deformation results in the development of dilational shear fractures, observed along the orogenic belt, at an angle of ～20^° from the principal compressive stress axis.     

Probabilistic risk assessment of major accidents: application to offshore blowouts in the Gulf of Mexico

Major accidents are low-frequency, high-consequence accidents which are not well supported by conventional statistical methods due to the scarcity of directly relevant data. Modeling and decomposition techniques such as event tree have been proved as robust alternatives as they facilitate incorporation of partially relevant near accident data–accident precursor data—in probability estimation and risk analysis of major accidents. In this study, we developed a methodology based on event tree and hierarchical Bayesian analysis to establish informative distributions for offshore blowouts using data of near accidents, such as kicks, leaks, and failure of blowout preventers collected from a variety of offshore drilling rigs. These informative distributions can be used as predictive tools to estimate relevant failure probabilities in the future. Further, having a set of near accident data of a drilling rig of interest, the informative distributions can be updated to render case-specific posterior distributions which are of great importance in quantitative risk analysis. To cope with uncertainties, we implemented the methodology in a Markov Chain Monte Carlo framework and applied it to risk assessment of offshore blowouts in the Gulf of Mexico.     

Photo-induced degradation of emamectin benzoate: effect of iron amendments and solvent system

Photodegradation is the major dissipation pathway for emamectin benzoate (EB) in water. Therefore, the photolysis of EB was studied in distilled water (DW) and methanol under different irradiation conditions such as natural sunlight, UV tube, and artificially stimulated light (mercury lamp 125 W). The results of the study showed that EB degrades rapidly in DW than in methanol as evidenced by a photodegradation efficiency of about 75 % achieved in DW, after 24 h of irradiation with UV light, while in methanol, it was only 59.3 %. The addition of iron to EB solution in DW further enhanced its photodegradation. The rate of photodegradation of EB was recorded to be increased from 5.5 × 10^?2 to 1.0 × 10^?1 k/h after amendment with iron. The order for the rate of photodegradation of EB was DW + Fe > DW > methanol, with their respective t _1/2 values of 6.5, 12.6, and 18.7 h. Fe amendment was also found to enhance the degradation efficiency of EB even in the absence of any light (dark).     

Petrofacies,provenance, and paleocurrent analysis of Pachmarhi sandstone (Early Triassic), Satpura basin,Central India

The Satpura Gondwana basin hosts a ～5 km thick siliciclastic succession that unconformably overlies the Precambrian basement. The Gondwana sequence in this basin starts from Early Permian (Talchir Formation) to Lower Cretaceous (Jabalpur Formation). The aim of this study is to (1) identify the source rock (provenance) for Early Triassic Pachmarhi sediments in the Satpura Gondwana succession and (2) to understand the relative role of tectonics and climate in determining the sandstone composition. These sandstones are medium to coarse-grained, moderately to moderately well sorted, subangular to subrounded, of moderate sphericity, and composed of several varieties of quartz, feldspar, rock fragments, and micas. Petrographically, the Pachmarhi sandstones are mostly quartzarenite and subarkose. The petrofacies in Qt–F–L and Qm–F–Lt triangular diagrams show that the bulk of the Pachmarhi was derived from continental (cratonic) source, especially from craton interior. Petrofacies, together with paleocurrent data, suggest that Pachmarhi Formation was deposited by a network of braided river system, which flowed dominantly from southeast to northwest. The study suggests that the sediments were mostly derived from Precambrian granites, gneiss, and metasedimentary basement rocks straddling the southern margin of the basin. Paleocurrent data also corroborates this contention.     

Dominant impact of South Asian low heat on summer monsoon rainfall over Central India

Although previous literature have considered Southern Oscillation Index (SOI), Indian Dipole, and SST as the major teleconnection patterns to explain the variability of summer monsoon rainfall over India. South Asia low pressure and Indian Ocean high are the centers of action that dominates atmospheric circulations in Indian continent. This paper examines the possible impact of South Asian low pressure distribution on the variability of summer monsoon rainfall of India using centers of action approach. Our analysis demonstrates that the explanation of summer monsoon rainfall variability over Central India is improved significantly if the SOI is replaced by South Asian low heat. This contribution also explains the physical mechanisms to establish the relationships between the South Asian low heat and regional climate by examining composite maps of large-scale circulation fields using NCEP/NCAR Reanalysis data.     

Facies analysis and depositional environment of the Jurassic, Jumara Dome sediments, Kachchh, western India

The study deals with the depositional environment of Jumara Dome sediments. The Jumara Dome is an important outcrop of Bathonian to Oxfordian sediments amongst the Kachchh Mainland exposures. On the basis of facies analysis three associations have been documented, namely, G-1 consisting of low energy facies comprising of cross-bedded sandstone, massive sandstone, grey shale and thin bedded sandstone, bioclastic — lithoclastic grainstone, bioclastic — lithoclastic packstone, microbioclastic packstone/wackestone, bioturbated laminated wackestone to mudstone and pelagic lime mudstone; G-II consisting of moderate energy facies comprising of laminated sandstone and grapestone or agglutinated grainstone; G-III consisting of high energy facies comprising of interbedded gypsiferous shale and sandstone/siltstone, oolitic grainstone to conglomerate and bioclastic grainstone. The facies associations reflect an ideal shallowing upward sequence representing slope, bioclast bar, lagoon and inner shelf. Presence of wide range of facies indicates that the rocks of the studied area were deposited during the fluctuating sea level, interrupted by the storms, in the shallow marine environment.     

Soft X-ray observation of a large-scale coronal wave and its exciter

Recent extreme ultraviolet (EUV) observations from SOHO have shown the common occurrence of flare-associated global coronal waves strongly correlated with metric type II bursts, and in some cases with chromospheric Moreton waves. Until now, however, few direct soft X-ray detections of related global coronal waves have been reported. We have studied Yohkoh Soft X-ray Telescope (SXT) imaging observations to understand this apparent discrepancy, and describe the problems in this paper. We have found good X-ray evidence for a large-scale coronal wave associated with a major flare on 6 May 1998. The earliest direct trace of the wave motion on 6 May consisted of an expanding volume within 20 Mm (projected) of the flare-core loops, as established by loop motions and a dimming signature. Wavefront analyses of the soft X-ray observations point to this region as the source of the wave, which began at the time of an early hard X-ray spike in the impulsive phase of the flare. The emission can be seen out to a large radial distance (some 220 Mm from the flare core) by SXT, and a similar structure at a still greater distance by EIT (the Extreme Ultraviolet Imaging Telescope) on SOHO. The radio dynamic spectra confirm that an associated disturbance started at a relatively high density, consistent with the X-ray observations, prior to the metric type II burst emission onset. The wavefront tilted away from the vertical as expected from refraction if the Alfvén speed increases with height in the corona. From the X-ray observations we estimate that the electron temperature in the wave, at a distance of 120 Mm from the flare core, was on the order of 2–4 MK, consistent with a Mach number in the range 1.1–1.3. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022904125479 deceased