Godavari Basin Research Articles

Multiproxy geochemical characterization of Kommugudem Formation, Krishna Godavari Basin, India: Implication on hydrocarbon potential and shale brittleness

The unconventional reserves are vital future energy resources and globally augmented interest endeavours the discovery of gas and oil‐rich shales. The Kommugudem Formation, Krishna Godavari Basin was evaluated based on sample laboratory and well log studies from six wells deciphering mineralogical and organic geochemical parameters to provide an understanding of hydrocarbon potential and brittleness. Kommugudem Formation constitutes Type III kerogen dominantly with high total organic carbon (TOC) and Tmax indicating the presence of high organic matter. The mean vitrinite reflectance indicates mature to post‐mature shale majorly in the gas generation window. Fourier transform infrared spectroscopy functional group investigation revealed the presence of aromatics and aliphatics with a higher degree of abundance owing to higher TOC content. The basic well logs recorded in the studied region are used to estimate the continuous TOC and porosity of the formation and corroborate with laboratory core data. Petrographic, X‐ray diffraction, and field emission scanning electron microscopy studies revealed the presence of dominantly siliceous mineral matter with relatively lower clay and carbonates. Organic mudstone classification indicates formation is dominantly silica‐dominated lithotype and clay‐rich siliceous mudstone. Microfractures and micropores are observed in mineral and organic matter that may act as storage sites for hydrocarbons. Kommugudem Formation on the basis of mineralogy indicates compositional analogy with brittle zones of Barnett Shale Formation. The high mineralogical brittleness index of the Kommugudem Formation indicates good conditions for hydraulic fracturing. The present investigation demonstrates excellent hydrocarbon generation potential and good brittleness in wells A and B while C, D, E, and F have relatively lower potential and may have low gas and oil sources.

High Resolution Biostratigraphy of Post-Gondwana Pre-Cretaceous and Cretaceous successions from Pennar Sub-basin, Krishna- Godavari Basin, India

High Resolution Biostratigraphy of Post-Gondwana Pre-Cretaceous and Cretaceous successions from Pennar Sub-basin, Krishna- Godavari Basin, India

Establishing optimal nutrient norms in leaf and soil for oil palm in India

Diagnosis and recommendation integrated system (DRIS)-based critical and optimum leaf nutrient standards for oil palm (OP) (Elaeis guineensis Jacq) have been estimated for some locations of India to find out the most critical nutrients. However, a well-established boundary line approach has not been evaluated for defining optimal ranges of leaf nutrients. Further, no defined standards are available for soil available nutrients in oil palm growing regions of India. Nutrient management in oil palm gains paramount importance due to its huge requirement as well as its spectacular influence on fresh fruit bunch (FFB) and oil yields. Therefore, apt norms need to be established for better productivity through precise nutrient management. With this objective, optimum concentrations for the most important leaf nutrients, their sufficiency ranges, nutrient ratios and their optimal ranges have been determined by employing boundary line approach and the results have been compared with that of DRIS approach based on average values of high yielding populations. Similarly, optimal soil available nutrient status in terms of optimal concentrations and their sufficiency ranges also have been standardized for oil palm and compared with DRIS method. For Krishna – Godavari basin area of Andhra Pradesh in India, the optimal concentrations of nutrients in oil palm leaves were established as 2.64, 0.16, 0.78, 1.3, 0.52, 0.16% for nitrogen (N), phosphorus (P), potassium (K), Calcium (Ca), Magnesium (Mg) and sulphur (S). For boron (B) the optimal concentration is 69.8 mg kg−1 through BLA approach. For the same area, the optimal values of soil available nutrients were 452, 144, 388 kg of N, P2O5 and K2O per ha, 1.96 and 1.7 meq 100 g−1 of Ca and Mg respectively, and 68 mg kg−1 for SO4-S and 8.4 ppm for B. The optimal pH level was 6.6. A variation of up to 10% was recorded between DRIS and boundary line approach and for better management optimal nutrient standards need to be established for each agro-eco region.

Development of one dimensional geomechanical model for a tight gas reservoir

Estimating rock-mechanical, petrophysical properties and pre-production stress state is essential for effective reservoir planning, development, and optimal exploitation. This paper attempts to construct a comprehensive one-dimensional mechanical earth model (1D MEM) of the Mandapeta gas reservoir of Krishna Godavari (KG) basin, India. The methodology comprises a detailed stepwise process from processing and analysis of raw log data, calibration of log-derived dynamic properties with static ones using regression models developed from tested core samples, and final rock mechanical property estimation. Pore pressure profiles have been estimated and calibrated with the Repeat formation tester (RFT) data for every thirty-five wells. Overburden and horizontal stresses have also been evaluated and calibrated using data from the Leak-off Tests (LOT) or Extended Leak-off Tests (XLOT). A menu-driven program is developed using PYTHON code for visualization and on-time revision of 1D MEM. The resulting comprehensive 1D MEM predicts and establishes the rock-mechanical properties, pore pressure, and in-situ stress values of the basin. Besides its use in planning future wells, development of the field, and yielding insight into the various well challenges, it can also be used to develop a 3D MEM of the reservoir.

Assessment of rainfall trend and variability of semi-arid regions of Upper and Middle Godavari basin, India

Abstract Study of rainfall pattern and trend in the long term is essential from climatic change and socioeconomic perspectives. In the present study, monthly, seasonal and annual rainfall of semi-arid regions (Madhya Maharashtra, Marahwada and Vidarbha) of the Godavari basin is evaluated for the period of 1871–2016. The innovative trend analysis (ITA), Mann–Kendall test (MK) and Sen's slope estimator methods are used to check gradual change. A significant increasing or decreasing trend is not detected in the seasonal and annual rainfall series for any of the regions. The rainfall variability index indicates Madhya Maharashtra has received normal rainfall for 40% of the time, Marathwada for 36% of the time and Vidarbha region for 41% of the time. Very dry and very wet conditions are experienced by all three regions for 15% of the time. The spatial and temporal variation in the seasonal and annual rainfall is not significant in these regions. The results obtained from the study will be useful for water resource management of the Godavari basin.

Benthic Foraminiferal Response to the Millennial-Scale Variations in Monsoon-Driven Productivity and Deep-Water Oxygenation in the Western Bay of Bengal During the Last 45 ka

In this study, we presented a high-resolution benthic foraminiferal assemblage record from the western Bay of Bengal (BoB) (off Krishna–Godavari Basin) showing millennial-scale variations during the last 45 ka. We studied temporal variations in benthic foraminiferal assemblages (relative abundances of ecologically sensitive groups/species, microhabitat categories, and morphogroups) to infer past changes in sea bottom environment and to understand how monsoon induced primary productivity-driven organic matter export flux and externally sourced deep-water masses impacted the deep-sea environment at the core site. Our records reveal a strong coupling between surface productivity and benthic environment on glacial/interglacial and millennial scale in concert with Northern Hemisphere climate events. Faunal data suggest a relatively oxic environment when the organic matter flux to the sea floor was low due to low primary production during intensified summer monsoon attributing surface water stratification and less nutrient availability in the mixed layer. Furthermore, records of oxygen-sensitive benthic taxa (low-oxygen vs. high-oxygen benthics) indicate that changes in deep-water circulation combined with the primary productivity-driven organic matter flux modulated the sea bottom oxygen condition over the last 45 ka. We suggest that the bottom water at the core site was well-ventilated during the Holocene (except for the period since 3 ka) compared with the late glacial period. At the millennial timescale, our faunal proxy records suggest relatively oxygen-poor condition at the sea floor during the intervals corresponding to the cold stadials and North Atlantic Heinrich events (H1, H2, H3, and H4) compared with the Dansgaard/Oeschger (D-O) warm interstadials. The study further reveals oxygen-poor bottom waters during the last glacial maximum (LGM, 19–22 ka) which is more pronounced during 21–22 ka. A major shift in sea bottom condition from an oxygenated bottom water during the warm Bølling–Allerød (B/A) (between 13 and 15 ka) to the oxygen-depleted condition during the cold Younger Dryas (YD) period (between 10.5 and 13 ka) is noticed. It is likely that the enhanced inflow of North Atlantic Deep Water (NADW) to BoB would have ventilated bottom waters at the core site during the Holocene, B/A event, and probably during the D-O interstadials of marine isotope stage (MIS) 3.

Impact of sedimentary environment on pore parameters of thermally mature Permian shale: A study from Kommugudem Formation of Krishna Godavari Basin, India

The pores are significant factors to assess the fracture system of a shale reservoir. The present study evaluates organic matter-associated parameters, redox condition, paleoclimate and paleosalinity and their role on the pore structure of thermally mature Kommugudem shale of Krishna Godavari Basin. The XRD analysis supported by FE-SEM mainly indicates silica-dominated lithotype and clay-rich siliceous mudstone in the Kommugudem Formation. Intercrystalline and intracrystalline pores were observed in association with mineral and organic matter that provide storage sites for hydrocarbon. Excellent TOC content and genesis of gas prone, type III kerogen dominantly observed in admixture with type II or type IV kerogen. The clay, TOC and Tmax have a positive correlation with micropore volume indicating a good contribution of clay micropore and associated organic matter. Fractal dimensions were estimated using the fractal FHH method with an average value of 2.65 suggesting that the pore surfaces are rough and exhibit complex and heterogeneous pore structure. The Kommugudem Formation constitutes detrital sediments sourced from felsic volcanic rocks in humid and warm climate along the passive tectonic continental margin. The redox and paleosaline investigations reveal the fluvio-marine transitional environment preserved under suboxic to oxic conditions. The REEs and trace elements are positively correlated with pore volume indicating their possible role in the pore genesis of silicate minerals and corroborating the positive influence of the environment. The redox proxies are strongly correlated with TOC and pore volume supports the probable development of organopores. The investigation reveals the significant role of multiproxy paleoenvironmental indices to understand the complex mechanism of pore characteristics.

Pan evaporative changes in transboundary Godavari River basin, India

Pan evaporative changes are one of the key components of water resources management of a river basin under changing climate and anthropogenic-induced warming. The present study was undertaken for transboundary Godavari River basin (India) to identify the trends in pan evaporation (Epan) by non-parametric Mann–Kendall (MK) test in annual, seasonal and monthly time scales. The Pettitt test, a non-parametric test, was also used in this study to detect abrupt changes in the mean of the distribution of the Epan in the Godavari basin. Furthermore, the stepwise regression analysis was performed to find out the cause of the observed Epan changes in the basin. On seasonal (monthly) time scales, statistically significant decreasing trends in Epan were witnessed in the pre-monsoon season (in the months of March, April and May) in all the seven sites of the Godavari River basin. On the other hand, four sites witnessed statistically significant increasing trends in minimum temperature (maximum temperature) in the month of July (December) and in the monsoon (post-monsoon) season in the Godavari River basin. Statistically significant decreasing (increasing) trends in wind speed (relative humidity) in the pre-monsoon season and in the month of March at these seven sites support the observed decline in the evaporative demand in the basin leading to possible enhancement in the total yield of the Godavari River basin. Results of stepwise regression analysis showed that wind speed followed by relative humidity was found to be two main causative parameters of the observed decline in the Epan under the warmer environments in the Godavari River basin. Pettitt’s test shows year 1991–1992 to be the probable year of change in the Epan in the Godavari River basin.

Gravity inversion of basement relief using Particle Swarm Optimization by automated parameter selection of Fourier coefficients

A global optimization technique using particle swarm optimization (PSO) is presented to estimate the depth to the basement of a heterogeneous sedimentary basin from the vertical component of the residual gravity anomalies. Inversion of basement relief for known density distributions has particular importance in many real applications such as mineral exploration, geothermal exploration, etc. Generally, gravity inversion in the Fourier domain allows a reduction in the optimization parameter. However, in the present study, an automated parameter selection criterion is developed for further reduction of optimizing parameters. A detailed uncertainty appraisal analysis is also performed for different configurations of synthetic models, which ensures the reliability of the optimization technique. All synthetic models are contaminated with white Gaussian noise, and an optimized depth profile is compared with noise-free data for sensitivity analysis. The result shows the robustness of the optimization method in the presence of noise. The technique is implemented on two real gravity anomaly profiles (1) Godavari basin, India, and (2) Sayula basin, Mexico. The optimized depth profile shows a good agreement with the published results using other optimization techniques. The method developed in the present work is a novel approach for the automatic selection of parameters as per the model’s complexity. It provides an inversion technique that considers a small number of parameters with a minimum computational expense.

Recent decline in streamflow and sediment discharge in the Godavari basin, India (1965–2015)

Godavari River representing the largest catchment in Peninsular India records a significant decline in streamflow and sediment discharge since 1965 with a sharp fall after ~1990. The present study documented changes in water and sediment discharge based on analysis of a large time-series database of daily streamflow from 57 gauging stations and sediment discharge from 25 stations during the period from 1965 to 2015 in the Godavari basin. Linear regression, Mann-Kendall non-parametric test, Sen’s slope, and Pettitt tests were conducted to examine the trends and abrupt changes in the time series. Many stations recorded a decline in sediment discharge (up to 90%) after 1990. At the terminal gauging station (Polavaram), the average annual sediment discharge for the period between 1970 and 1990 was 142 × 106 t, while it decreased to 59 × 106 t from 1991 to 2013. The outcomes of this study revealed a critical drop in sediment discharge after 1990 because of very high sediment entrapment by extensive dam constructions. This resulted in a substantial decrease in sediment supply contrasting to the increasing sea level, further implicating significant coastal erosion in the near future.

Comprehensive Rock Physics, Petrophysics workflow to correct Sonic Logs for improved seismic QI: Study using wells of Krishna Godavari basin

Rock physics analysis uses well log data as direct measurement of physical properties of the subsurface formations. Hence, in seismic reservoir characterisation they do not suffer the same level of scrutiny as seismic. Mud-filtrate invasion during drilling contaminates porous formation affecting log responses in non-intuitive ways. Ignoring invasion effect on well logs prior to quantitative petrophysical interpretations may led to erroneous reserve estimates as well as well-to-seismic misties. In addition, sonic logs are prone to ambiguity incorporated by weak waveform generation and non-unique coherence picking. This gives rise to non-unique compressional and shear slowness data. To correct the invasion affected logs, we have designed a workflow that effectively improves the recorded data. This workflow uses modified Gassmann (1951) fluid replacement modelling (FRM) method for sonic data correction. In addition, following an improved coherence picking we get a further updated sonic slowness. Using the corrected data in synthetic seismic generation enables us to achieve substantial improvements in synthetic-seismic correlation values. Furthermore, use of updated data results in a better three way matching with vertical seismic profiling (VSP) data.

Gas hydrate/free gas migration pathways in submarine slope failures: East Indian Margin

Gas hydrates from the continental margin settings are mostly confined to continental slopes. The free gas occurring below the gas hydrate laden sediments play a crucial role in the submarine slope failures and can potentially trigger the submarine landslides. The present study is carried out to investigate such a scenario in the shale dominated Krishna–Godavari (KG) basin having proven gas hydrate deposits. Shale reservoirs are less permeable compared to sandstone reservoirs and as such, the free gas that is locked in the pore spaces of shales would eventually create hydro fractures or faults to escape from the pore spaces. This overpressure from the gas zone will find a pathway to reach the shallower depths. In the present study, two faults are identified of which, one is acting as a potential pathway for overpressures to travel through it, while the other is found to be critically pressurized due to the gas zone below it. The calculated gas column height is ~51 m and any further increase in the gas column height would create a fault slip and cause the mechanical failure of the sediments, creating another potential pathway. We infer that these faults are acting as a migration pathway in our study area and the advection of fluid/gas from the gas zone via the pathway might have played a major role in creating a slope break above the fault.

Regional analysis of drought severity‐duration‐frequency and severity‐area‐frequency curves in the Godavari River Basin, India

AbstractIndia is one of the most drought‐ravaged countries in the world and faces at least one drought in one region or another in every 3 years. There is no single reliable approach in characterizing future droughts. To understand future drought risk, potential changes of drought properties and characteristics are analysed in this study. Using Fuzzy c‐means clustering approach, homogeneous drought regions are identified in the Godavari river basin and therefore, optimum number of clusters were assigned as four. The 12‐month standardized precipitation index (SPI) using precipitation data from India Meteorological Department (IMD) and Global Climate Model (GCM)—MIROC‐ESM‐CHEM is calculated for the homogeneous regions of the Godavari basin. The best fit copula for observed and simulated severity and duration are: Region 1—Clayton, Regions 2 and 3—Gumbel, Region 4—Frank copula. Severity‐duration‐frequency (SDF) and severity‐area‐frequency (SAF) curves were developed and analysed using the best fit copulas. The research findings conclude that moderate and severe droughts are frequently increasing for future periods (2006–2099) compared to the historic period (1962–2005). Droughts with high severity and high mean interarrival time are observed as expected in the future. For the Godavari basin, the SDF curves were concave upwards indicating an increase in severity with an increase in duration. The rate of increase of severity is small for shorter durations compared to that of longer‐duration drought. Thus, more prolonged drought events in the 21st century are likely to occur. The SAF curves with steeper slopes and high variability in topographical and hydrological characteristics have been observed over the Godavari basin. From these curves, for a specified percentage of area and return period, the drought severity can be calculated and the information can be used for crop management and agricultural water demands. Overall, the findings of this research offer a view of likely scenarios of drought in the Godavari basin.

Multi-Spatial Resolution Rainfall-Runoff Modelling—A Case Study of Sabari River Basin, India

One of the challenges in rainfall-runoff modeling is the identification of an appropriate model spatial resolution that allows streamflow estimation at customized locations of the river basin. In lumped modeling, spatial resolution is not an issue as spatial variability is not accounted for, whereas in distributed modeling grid or cell resolution can be related to spatial resolution but its application is limited because of its large data requirements. Streamflow estimation at the data-poor customized locations is not possible in lumped modeling, whereas it is challenging in distributed modeling. In this context, semi-distributed modeling offers a solution including model resolution and estimation of streamflow at customized locations of a river basins with less data requirements. In this study, the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) model is employed in semi-distribution mode on river basins of six different spatial resolutions. The model was calibrated and validated for fifteen and three selected flood events, respectively, of three types, i.e., single peak (SP), double peak (DP)- and multiple peaks (MP) at six different spatial resolution of the Sabari River Basin (SRB), a sub-basin of the Godavari basin, India. Calibrated parameters were analyzed to understand hydrologic parameter variability in the context of spatial resolution and flood event aspects. Streamflow hydrographs were developed, and various verification metrics and model scores were calculated for reference- and calibration- scenarios. During the calibration phase, the median of correlation coefficient and NSE for all 15 events of all six configurations was 0.90 and 0.69, respectively. The estimated streamflow hydrographs from six configurations suggest the model’s ability to simulate the processes efficiently. Parameters obtained from the calibration phase were used to generate an ensemble of streamflow at multiple locations including basin outlet as part of the validation. The estimated ensemble of streamflows appeared to be realistic, and both single-valued and ensemble verification metrics indicated the model’s good performance. The results suggested better performance of lumped modeling followed by the semi-distributed modeling with a finer spatial resolution. Thus, the study demonstrates a method that can be applied for real-time streamflow forecast at interior locations of a basin, which are not necessarily data rich.

Groundwater Potential Zone Delineation in Hard Rock Terrain for Sustainable Groundwater Development and Management in South Madhya Pradesh, India

In view of the vital significance of water resources and issues emerging from their temporal and spatial distribution and utilization posing serious problems to the land resources and to the society United Nations has identified sustainable management of water resources (SDG 6) as one of the seventeen major Sustainable Development Goals (SDGs). In this perspective, the purpose of the study is to identify the groundwater potential zones in the hard rock terrain of Betul-Chhindwara Region, Madhya Pradesh, India, using AHP technique. The study area comprises the sub-watersheds of Tawa river (Narmada basin), Tapi river (Tapi basin), Kanhan and Pench rivers (Godavari basin). Various thematic layers such as geomorphology, geology, physiography, rainfall, soil, slope, lineament, drainage density, groundwater depth, and land use/ land cover were developed. The analytical hierarchy process helps to delineate groundwater prospect zones, which are categorized into five classes, i.e. very poor, poor, moderate, good, and very good based on objective, criteria, and preference. The good, moderate, and poor groundwater potential zones cover 4815 sq. km., 6423 sq. km, and 4857 sq. km, respectively, comprising 22.46%, 29.96%, and 22.65% of the entire region under study. The result indicates that 15.22% of the area comprising 3262.10 sq. km have very good groundwater potential whereas 9.71% (2080 sq. km) has very poor groundwater potential. The obtained result has been verified through field check based on the yield data collected from 16 bore wells in the study area. The accuracy of the results was 75% that proves the efficiency of the adopted techniques. Thus, this study will be efficient for the sustainable development and management of groundwater in the study area.

Genome sequencing and analysis of a psychrotrophic methanogen Methanosarcina sp. nov. MSH10X1 cultured from methane hydrate deposits of Krishna Godavari Basin of India.

Methanosarcina sp. strain MSH10X1, a psychrotrophic methanogen, was isolated from sub-seafloor methane hydrate deposits of Krishna Godavari Basin on India's east coast. The strain could grow from 5 to 40°C following all three i.e. methylotrophic, acetoclastic, and hydrogenotrophic modes of methanogenesis utilizing different substrates like methanol, trimethylamine, H2/CO2 (80/20), acetate, valerate, isobutyrate, isopropanol, and isobutanol. The genome sequencing and analysis of this strain revealed a circular chromosome of 3,557,383bp length having 42.47mol%G+C content, which consisted of 3110 coding genes, 58 tRNA genes, and 3 rRNA operons. The KEGG analysis highlighted the presence of genes responsible for all three modes of methanogenesis. The presence of genes like mtaB, mtaC, and mttB in the genome provided evidence for possible adaptation of strain MSH10X1 in the deep sea's low-temperature conditions.

Large scale reservoir operation through integrated meta-heuristic approach

Reservoir optimization models are often large-scale, having a complex, nonlinear, multi-dimensional structure, which poses a challenge for classical methods for their solution. This has encouraged the researchers to focus on Meta-heuristic which due to their flexible and adaptive nature have been successful in solving a plethora of real-life optimization problems. This study brings forward an implementation and comparison of six well-known Meta-heuristics namely: Simulated Annealing, Genetic Algorithms, Particle Swarm Optimization, Differential Evolution, Artificial Bee Colony, and Cuckoo Search and an integrated version of these algorithms with dynamic programming for optimizing the reservoir operations policy. In addition, two adaptive variants of DE named: FCADE2 and SaDE are also considered for the comparison. The case study considered for Mula reservoir supplying water to Major Irrigation Project on River Mula (Godavari basin), Ahmednagar district, Maharashtra, India. The objective is to determine the optimum release policy for Mula reservoir. Performance of the algorithms is analysed on two data sets (1) single year and (2) 30-years.

On further specimens of the Pit viper Trimeresurus erythrurus (Cantor, 1839) (Squamata: Viperidae), with description of a topotype and range extension to the Godavari Basin, peninsular India

We report on a topotypical specimen of the spot-tailed pit viper Trimeresurus erythrurus recorded from Sunderbans in India and a distant, southerly, range extension from Kakinada mangroves, based on preserved (n= 1, seen in 2019) and live uncollected (n= 2; seen in 2014) specimens, respectively. The specimens (n= 3) share the following characteristics: verdant green dorsum, yellow iris, white ventrolateral stripes in males, 23 midbody scale rows, 161–172 ventrals, 61–76 subcaudals, and reddish tail tip. Drawing on the published records, its apparent rarity within its type locality and lack of records from the Circar Coast of India, our study significantly adds to the knowledge of the distribution and morphology of this species. Being a medically important venomous snake, its presence in the Godavari mangrove basin calls for wider dissemination of this information among medical practitioners, in addition to fundamental researchers like academics and herpetologists.

Subsurface porosity estimation: A case study from the Krishna Godavari offshore basin, eastern Indian margin

Porosity is one of the fundamental petrophysical parameters essential for appraisal of hydrocarbon reserve and planning production operations. Several interpretation techniques have evolved over time that allows geologists to meticulously estimate reservoir properties by integrating seismic and borehole data. The present study investigates the use of Multi-Attribute Transform Method (MATM) and Artificial Neural Networks (ANN) for the delineation of lateral variation of porosity along a 2D seismic reflection dataset in the gas hydrate inferred area of Krishna–Godavari basin, eastern Indian margin. The best set of attributes that can predict the porosity are derived using multi-attribute regression analysis. These attributes are applied in MATM and are also used to train the neural networks. This is achieved using different networks of neural computation like Probabilistic Neural Network (PNN), Multi-Layer Feedforward Network (MLFN) and Radial Basis Function (RBFN) with an aim to decipher an optimized approach best suits to predict porosity of the study area. The correlation between observed and predicted porosity logs are tested both by cascading and non-cascading the networks with the MATM. The predictive power is found improved as we progress from MATM to neural network cascaded with the trend of MATM. Finally, it is observed that PNN cascaded with the results of MATM shows the least prediction error than the other networks.

A new acritarch spike of Leiosphaeridia dessicata comb. nov. emend. from the Upper Permian and Lower Triassic sequence of India (Pranhita-Godavari Basin): Its origin and palaeoecological significance

The Permian–Triassic Mass Extinction (PTME) event was the largest bio crisis to date, adversely affecting life on land and sea. The PTME event is evidenced in India by the destruction of glossopterids with immense loss of peat-forming vegetation, its replacement by stress-tolerant lycopsids, Lilliput Effect and the presence of numerous acritarchs and abnormal pollen grains. However, there are no reports for algal or acritarch spikes. We document, for the first time, an acritarch spike in the Indian subcontinent from the uppermost Permian to Lower Triassic sequence from the Pranhita–Godavari (P-G) Basin. Lithostratigraphically, the late Permian and Early Triassic aged deposits in the P-G basin are designated as the Kamthi Formation. The formation has a very rich and diverse assemblage of pollen grains, spores and acritarchs. Based on a palynological study, an abundance of Leiosphaeridia dessicata comb. nov. emend. has been identified from sediment samples from the two bore cores (MCP-7 and MCP-8) of the Chintalapudi sub-basin, P-G basin. The acritarch appearance and abundance occurred in synchronization with the floral shift. The acritarch appears along with the stress-tolerant lycopsid spores in the uppermost Permian assemblage and increases in accordance with lycopsid spores in the Lower Triassic assemblages.The morphology of Leiosphaeridia dessicata comb. nov. emend. relates its close affinity with an extant marine algal cyst of Acetabularia acetabulum. Moreover, the presence of gammacerane and methylate chromans in the host sediment indicates the hypersaline water column during the deposition. Thus, based on the presence of marine and hypersaline biomarkers and affinity of L. dessicata comb. nov. emend. with marine alga (probably Prasinophyceae or Chlorophyceae) infer that the deposition during the uppermost Permian and Lower Triassic occurred under shallow marine conditions, contradictory to the earlier belief that Indian Upper Permian and Triassic deposits are entirely terrestrial. The possible marine incursion in the P-G basin may have occurred from the eastern continental margin along western Australia or through a passage between the Indian southern margin and the west margin of Antarctica.