Geochemistry of volcanic glass from Mahanadi offshore region,eastern continental margin of India:Constraints on the contribution of latest Toba super-eruption

The tephra layers in multiple sediment cores from the offshore region of the Mahanadi basin in the northern Bay of Bengal were investigated for possible volcanic sources. The glass shards from those tephra layers were studied for size distribution, texture, and elemental geochemistry to establish chronostratigraphic markers for regional and global Quaternary correlation. The textural features of fine-grained(silty) volcanic glasses suggest the distal source of these tephra deposits. Major element composition with elevated SiO_(2) contents ranging between75%–76% and dominance of K_(2)O(> 4.5%) over CaO(< 0.9%) suggest ashes have originated from siliceous rhyolitic melts, similar to the petrographic composition of tephra from the Toba volcano. The bulk trace element compositions of the same glass shards were comparable with those reported in the youngest Toba tephra reported elsewhere. Likewise, the LREE-dominated chondrite normalized REE profiles of tephra from the Mahanadi basin closely resemble the characteristic REE patterns in Toba ash from other parts of the Indian Ocean and thus confirmed the contribution of the youngest Toba super-eruption for this ash layers.

Development of Flood Forecasting System Using Statistical and ANN Techniques in the Downstream Catchment of Mahanadi Basin, India

The floods in river Mahanadi delta are due to either dam release of Hirakud or due to contribution of intercepted catchment between Hirakud dam and delta. It is seen from post-Hirakud periods (1958) that out of 19 floods 14 are due to intercepted catchment contribution. The existing flood forecasting systems are mostly for upstream catchment, forecasting the inflow to reservoir, whereas the downstream catchment is devoid of a sound flood forecasting system. Therefore, in this study an attempt has been made to develop a workable forecasting system for downstream catchment. Instead of taking the flow time series concurrent flood peaks of 12 years of base and forecasting stations with its corresponding travel time are considered for analysis. Both statistical method and ANN based approach are considered for finding the peak to reach at delta head with its corresponding travel time. The travel time has been finalized adopting clustering techniques, there by differentiating high, medium and low peaks. The method is simple and it does not take into consideration the rainfall and other factors in the intercepted catchment. A comparison between both methods are tested and it is found that the ANN methods are better beyond the calibration range over statistical method and the efficiency of either methods reduces as the prediction reach is extended. However, it is able to give the peak discharge at delta head before 24 hour to 37 hour for high to low peaks.

印度Mahanadi盆地井下二叠纪下冈瓦纳岩层的微体植物化石组合(英文)

Mahanadi河盆地的冈瓦纳型诸盆地位于印度的近中心地区,呈北西-东南走向分布。Mahanadi主要盆地内的几个重要煤田为Korda煤田,Mand-Raigarh煤田和Ib河煤田。Korda煤田的冈瓦纳系沉积向南东向延伸,经Mand-Raigarh煤田延续至Ib河煤田。Korda和Ib河两个煤田储量巨大,且长期来有小构造活动;而Mand-Raigarh煤田至今很少受到重视,勘探开发晚得多。 文中首次对Mand-Raigarh煤田5个钻孔样品作了孢粉研究,以初现面、相对丰度等为特征,划分出7个孢粉组合带,时代从三叠纪最早期(Talchir组)至二叠纪末期(Raniganj组)。填补了东西两个煤田之间的生物地展研究空白。7个孢粉组合带为: i)Parasaccites-Plicatipollenites assemblage zone(相当于Talchir组), ii)Sulcatisporites-Brevitriletes assemblage zone(相当于下Barakar组), iii)Sulcatisporites-Rhizomaspora assemblage zone(少量Densipollenites存在说明其相当于上Barakar组), iv)Densipollenites-Striatopodocarpites assemblage zone(相当于Barren Measures组), v)Striatopodocarpites-Densipollenites assemblage zone(相当于下Raniganj组), vi)Striatopodocarpites-Densipollenites-Sulcatisporites assemblage zone(相当于上Raniganj组) vii)

Seasonal Variation of the Physicochemical Properties of Water Samples in Mahanadi Estuary, East Coast of India

The two major sources which are contributing to marine pollution are natural processes as well as anthropogenic activities. The natural process includes precipitation, erosion, weathering of crystal material whereas anthropogenic activities are urbanization, industrialization, mining and agricultural activities, etc. Mahanadi is the biggest river source of Odisha which joins the Bay of Bengal at Paradip. Paradip Township is an urbanized well-developed industrial township where various anthropogenic activities are contributing pollution to the water sources. In the present study, an attempt has been made to estimate and monitor the seasonal and spatial variation of physiochemical properties of the Mahanadi estuary, the East Coast coastal belt of India. The result revealed that there is a remarkable variation in the physiochemical parameters such as pH, salinity, TSS, DO, BOD, NO2N, NO3N, NH4N, TN, TP, SIO4 and Chl-a which are attributed to the runoff water getting discharged to the coastal water sources. It is being recommended to treat waste water and materials before discharging them to the marine water medium.

Provenance, Tectonics and Paleoclimate of Permo-Carboniferous Talchir Formation in Son-Mahanadi Basin, Central India with Special Reference to Chirimiri: Using Petrographical Interpretation

The present study deals with the petrographic interpretation of Talchir Formation sandstone, in and around Chirimiri area, Koriya district, Chhattisgarh state India located in Son-Mahanadi basin. This basin is an elongate graben showing northwest-southeast trend and considered to be one of the largest intra-cratonic rift basins of Indian peninsula. Talchir Formation is the lowermost unit of thick classical Gondwana sedimentary succession and rests unconformably on Precambrian basement. The petrographic studies consisting of point count show the presence of quartz as a dominant framework mineral with subordinate amounts of feldspars and rock fragments. The data plot in the fields of cratonic interior and transitional margin of continental block provenance. In the Qt (quartz)-F (feldspar)-L (lithic fragments) triangular diagram, indicating the source of these sediments was located in transitional margin and continental block provenance. The petrographic classification suggests that this formation in the study area dominantly contains compositionally immature to submature arkosic, sub-arkosic and lithic-arkosic sandstones. The bivariate plot between Qp/(F+R) vs. Qt/(F+R) indicates changes in climatic conditions from semi-arid to semi-humid during Permo-Carboniferous period.

应用电阻率和纵波速度估算印度Mahanadi盆地海洋沉积物天然气水合物饱和度

2006年，印度在国家天然气水合物计划（NGHP）第一航次钻探中于Mahanadi盆地东部大陆边缘发现了天然气水合物。对所获取的岩心进行红外成像分析证实了该区水合物主要以多层分散赋存。本文利用孔隙水化学分析、电阻率测井和声波速度测井来估算Mahanadi盆地三个站位（NGHP-01—08，NGHP-01—09和NGHP-01—19）的天然气水合物饱和度。利用孔隙水氯离子浓度异常估计位于天然气水合物稳定带底界（BGHSZ）之上海底200m以下的水合物饱和度最高为10％，利用电阻率测井和声波速度测井建模这两种方法估算的水合物饱和度值之间具有可比性，估算的值均在10％～15％之间变化。本文还对研究区的地震反射数据进行了分析，以识别天然气水合物存在的证据。该地区的BSR深度变化范围在海底以下200~300m之间，这取决于Mahanadi盆地的水深。基于区域地震资料发现天然气水合物存在与否与深水水道堤坝沉积复合体有关（尤其是在NGHP—01—19站位）。但是每个站位的取心或录井剖面都显示砂组分稀少，这就造成了水合物饱和度不会很高。从地震振幅时间切片来看，Mahanadi盆地所有钻孔均分布在河道体系陡坡地段中，而砂体绕过该地段沉积，所以推断重要的砂体沉积很可能出现在滑坡较远的地段，而从地震数据中可以推断出该较远地段沉积体系为典型的扇形沉积，因此可以预想在该较远地区可能存在更多的天然气水合物。

印度东部盆地群地质特征、油气成藏与深水区勘探潜力

基于印度东部盆地群区域构造沉积演化、地层充填和油气地质特征,建立深水扇体发育和成藏模式,分析深水区勘探潜力。印度东部被动大陆边缘形成源自东冈瓦纳古大陆裂解,经历了克拉通内裂谷(P_1—T)、东冈瓦纳裂谷(J_1—K_1)、裂后热沉降(K_2)和被动大陆边缘(K_3—N)4个演化阶段,发育裂后热沉降期末、被动大陆边缘I期末和Ⅱ期末3个明显不整合,形成裂谷期和被动大陆边缘Ⅰ期、Ⅱ期、Ⅲ期4套构造层,被动大陆边缘阶段沉积是盆地群地层主体,形成近岸叠覆型扇复合体、与三角洲有关的断裂坡折部位低位扇和前缘浊积扇两类富油气沉积体系。盆地内发育下二叠统、下白垩统、上白垩统和古近系4套证实的烃源岩,平面分布差异大;发育裂谷期砂岩和碳酸盐岩、裂后热沉降和被动大陆边缘时期三角洲和深水重力流砂岩等多种类型储集层,总体为中孔、低渗条件;油气盖层多、厚度变化大,漂移期多为区域封盖,其他时期则以局部封盖为主;形成上白垩统砂岩、古近系砂岩、新近系砂岩等8个成藏组合。被动大陆边缘阶段深水区油气勘探在平面上应以克里希那和高韦里河流三角洲地区为主,纵向上则以被动大陆边缘阶段与构造相关三角洲砂体、断裂坡折处低位扇、85°E海脊附近和高韦里盆地南部海域近岸扇复合体为重点。

Authigenic Gypsum in Gas-Hydrate Associated Sediments from the East Coast of India (Bay of Bengal)

Authigenic gypsum crystals, along with pyrite and carbonate mineralization, predominantly calcites were noticed in distinct intervals in a 32 m long piston core, collected in the gas hydratebearing sediments in the northern portion of the Krishna-Godavari basin, eastern continental margin of India at a water depth of 1691 m. X-ray diffraction and energy dispersive spectrum studies confirm presence of pyrite, gypsum, calcite, and other mineral aggregates. The occurrence of gypsum in such deep sea environment is intriguing, because gypsum is a classical evaporite mineral and is under saturated with respect to sea water. Sedimentological, geochemical evidences point to diagenetic formation of the gypsum due to oxidation of sulphide minerals （i.e. pyrite）. Euhedral, transparent gypsum crystals, with pyrite inclusions are cemented with authigenic carbonates, possibly indicating that they were formed authigenically in situ in the gas hydrate-influenced environment due to late burial diagenesis involving sulphate reduction and anaerobic oxidation of methane （AOM）. Therefore, the authigenic gypsums found in sediments of the Krishna-Godavari and Mahanadi offshore regions could be seen as one of the parameters to imply the presence of high methane flux possibly from gas hydrate at depth.

HEC-RAS Model for Mannnig’s Roughness: A Case Study

Channel roughness is considered as the most sensitive parameter in development of hydraulic models for flood forecasting and flood inundation mapping. Hence, it is essential to calibrate the channel roughness coefficient (Mannnig’s “n” value) for various river reaches through simulation of floods. In the present study it is attempted to calibrate and validate Mannnig’s “n” value using HEC-RAS for Mahanadi Riverin Odisha (India). For calibration of Mannnig’s “n” value, the floods for the years 2001 and 2003 have been considered. The calibrated model, in terms of channel roughness, has been used to simulate the flood for year2006 inthe same river reach. The performance of the calibrated and validated HEC-RAS based model has been tested using Nash and Sutcliffe efficiency. It is concluded from the simulation study that optimum Mannnig’s “n” value that can be used effectively for Khairmal to Barmul reach of Mahanadi Riveris 0.029. It is also verified that the peak flood discharge and time to reach peak value computed using Mannnig’s “n” of 0.029 showed only an error of 5.42% as compared with the observed flood data of year 2006.

A geospatial investigation of interlinkage between basement fault architecture and coastal aquifer hydrogeochemistry

The Mahanadi delta,deposited on a series of horst and graben basement structures,is considered an extension of the East Lambert Rift of Antarctica.Current study is based on the hydrogeochemical assessment of this deltaic aquifer system and geospatial analysis thereof,to appreciate the basement structure influence on groundwater chemistry.Major ion chemistry of subsurface waters portrays a distinct saline contamination across the terrain and varied regimes of water types,specifically with respect to southern and northern parts of this aquifer system.Findings of the study indicate a general near surface saline horizon and significant fragmentation of the hydrostatic units.This,in turn,implies noteworthy influence of formational water to salinity regimes and basin structural changes for the escape of these waters to surroundings.A plot of recent low intensity earthquakes displays proximity of epicenters to the faults as well as striking similarity to the trend of terrestrial faults indicating multiple reactivations of the faults.To further corroborate the above findings,spatial pattern analysis of individual hydrochemical variables is carried out which reveals specific clusters of sources(groundwater mixing)and sinks(groundwater dispersion) in proximity to basement fault dispositions.While the faults can be disregarded as conduits or barriers owing to their great depth,the overlying sedimentary mass,particularly,the horizons with significant clayey content have been distorted due to post rift subsidence and fault reactivations.A proximity analysis of ionic clusters points towards a greater influence of longitudinal faults to that of the transverse ones on groundwater mixing or dispersion.

Assessment of the fraction of bed load concentration towards the sediment transport of a monsoon-dominated river basin of Eastern India

Given the challenges of re-creating complex bed load(BL)transport processes in rivers,models are preferred over gathering and examining field data.The highlight of the present research is to develop an approach to determine the ungauged bed load concentration(BLC_(u))utilizing the measured suspended sediment concentration(SSC)and hydraulic variables of the last four decades for the Mahanadi River Basin.This technique employs shear stress and SSC equations for turbulent open channel flow.Besides,the predicted BLC_(u)is correlated with SSC using a power relation to estimate BLC_(u)on the river and tributaries.Eventually,different BL functions(BLF)efficiency is assessed across stations.The model predicted BLC_(u)is comparable with the published data for sandy rivers and falls within±20%.Outliers in hydraulic and sedimentological statistics significantly influence estimating the BL fraction apart from higher relative ratios and catchment geology.The constants of power functions are physically linked to sediment transport configuration,mechanism,and inflow to the stream.The stream power-based BLF best predicts the BL transport,followed by shear stress and unit discharge approaches.The disparity in the estimation of BLC_(u)results from station-specific physical factors,sampling data dispersion,and associated uncertainties.