• Volume 127, Issue 6

August 2018

• Reassembly of the Dharwar and Bastar cratons at ca. 1 Ga: Evidence from multiple tectonothermal events along the Karimnagar granulite belt and Khammam schist belt, southern India

The northern part of the Nellore–Khammam schist belt and the Karimnagar granulite belt, which are juxtaposed at high angle to each other have unique U–Pb zircon age records suggesting distinctive tectonothermal histories. Plate accretion and rifting in the eastern part of the Dharwar craton and between the Dharwar and Bastar craton indicate multiple and complex events from 2600 to 500 Ma. The Khammam schist belt, the Dharwar and the Bastar craton were joined together by the end of the Archaean. The Khammam schist belt had experienced additional tectonic events at ∼1900 and ∼1600 Ma. The Dharwar and Bastar cratons separated during development of the Pranhita–Godavari (P–G) valley basin at ∼1600 Ma, potentially linked to the breakup of the Columbia supercontinentand were reassembled during the Mesoproterozoic at about 1000 Ma. This amalgamation process in southern India could be associated with the formation of the Rodinia supercontinent. The Khammam schist belt and the Eastern Ghats mobile belt also show evidence for accretionary processes at around 500 Ma, which is interpreted as a record of Pan-African collisions during the Gondwanaassembly. From then on, southern India, as is known today, formed an integral part of the Indian continent.

• Assemblage of strike-slip faults and tectonic extension and compression analysis: A case study of a Lower Permian commercial coal reservoir in China

The Qinshui Basin was an active residual basin in the Mesozoic and Cenozoic periods and is located inside the North China Plate. The Upper Paleozoic strata in the basin have been strongly deformed and have developed a large number of strike-slip faults. The Qinshui Basin has been influenced by compressive stress from the northeast direction since the Himalayan period, and the faults have a dextral strike-slip property. Under the action of such a stress field, the right-slip, right-order faults indicate an extension region, and the right-slip, left-order faults indicate a compression region. Based on this principle, the extension and the compression areas were divided. From northwest to southeast direction in the study area, two types of regions have interactive distribution characteristics. For the Fanzhuang block in the eastern part of the study area, the fault distribution has an ‘S-type’ trend from north to south, and the middle extension region is the ‘elbow’ or the ‘hinge zone’ of the ‘S-type’ area, which can also be called the ‘stress transition zone’. The tectonic stress field of the stress transition zone is complex, and tensile fractures are usually extremely developed with extension tectonics. Gas wells with higher capacity are mainly distributed in the extension zone, while the capacity of the gas wells in the compression area is usually lower. The study showed that the distribution of the gas well capacity is consistent with the tectonic extension and compression analysis, indicating that the tectonic analysis method in this study is reliable. The Upper Paleozoic coal measure strata in the Qinshui Basin represent a whole gas-bearing and stress-bearing system, the tectonic analysis method in this study is also applicable to other types of tight reservoirs for this set of depositional systems.

• Assessing climate change impacts on river hydrology – A case study in the Western Ghats of India

The objective of this study is to evaluate the hydrological impacts of climate change on rainfall, temperature and streamflow in a west flowing river originating in the Western Ghats of India. The longterm trend analysis for 110 yr of meteorological variables (rainfall and temperature) was carried out using the modified Mann–Kendall trend test and the magnitude of the trend was quantified using the Sen’s slope estimator. The Regional Climate Model (RCM), COordinated Regional climate Downscaling EXperiment (CORDEX) simulated daily weather data of baseline (1951–2005) and future RCP 4.5 scenarios (2006–2060) were used to run the hydrological model, Soil and Water Assessment Tool (SWAT), in order to evaluate the effect of climate change on rainfall, temperature and streamflow. Significant changes were observed with regard to rainfall, which have shown decreasing trend at the rate of 2.63 mm per year for the historical and 8.85 mm per year for RCP 4.5 future scenarios. The average temperature was found to be increasing at 0.10 ◦C per decade for both historical and future scenarios. The impact of climate change on the annual streamflow yielded a decreasing trend at the rate of $\rm{1.2 Mm^{3}}$ per year and $\rm{2.56 Mm^{3}}$, respectively for the past and future scenarios. The present work also investigates the capability of SWAT to simulate the groundwater flow. The simulated results are compared with the recession limb of the hydrograph and were found to be reasonably accurate.

• GIS-based multi-criteria land suitability analysis for sustainable agriculture in the northeast area of Tadla plain (Morocco)

Assessment of soil suitability for sustainable intensive agriculture is an appropriate tool to select the land suitable for agricultural production with the least economic and environmental costs. This study was conducted to evaluate the agricultural soil quality in the northeast area of Tadla plain (Morocco) using geographic information system (GIS) and analytical hierarchy process (AHP). Six soil qualityindicators, i.e., pH, organic carbon, cation exchange capacity, texture, salinity and slope were considered and performed in 60 subsurface soil samples. AHP method was utilized to identify the weight of each indicator from the pairwise comparison matrix. The weighted sum overlay analysis was then used to generate the soil quality map in a GIS environment, by overlaying both indicator weights and subindicator weights. The studied area was classified into four soil quality categories, i.e., poor, medium, good, and excellent, the percentage of each category is 1.12, 20.98, 61.07 and 16.83%, respectively. The results indicated that 1.12% of the study area has poor suitability for sustainable intensive agriculturedue to their unsuitable texture and low salinity, while about 77% of cultivated soils are adapted to agricultural production. The above results could be useful for the management of agricultural activity.

• Moment of inertia for rock blocks subject to bookshelf faulting with geologically plausible density distributions

Moment of Inertia (MOI) for rock blocks that glided smoothly into book-shelf dispositions are deduced considering realistic linear and exponential 3D variations in density along specific axes/directions. Knowing (empirical) algebraic relations of density with depth, which could also be anything other than the exponential and linear variations considered in this work, geoscientists can deduce the MOI by following the same process. MOI for a homogeneous parallelepiped block along any direction is proportional to the length of the block in that direction. However, this simple relation does not hold true for rock blocks with variable densities. Nevertheless, as the block length increases, the MOI along that direction would also increase.

• Prioritization of soil conservation measures using erodibility indices as criteria in Sikkim (India)

Erodibility indices are important parameter that can be used to describe the intensity of the soil erosion problems causing environmental concerns. These indices are convenient to estimate the susceptibility to erosion where physical measurement is very difficult. Sikkim is one such state in India where measuringerosion is a tedious process due to its difficult and inaccessible terrain conditions. In the present study, spatial variation of susceptibility of erosion in East district of Sikkim was estimated by using indices such as clay ratio, dispersion ratio, mod clay ratio and critical level of soil organic matter. The result indicates soils in East district are mostly dominated by sand particles (40.5–81.06%) in majority of soilsamples. The dispersion ratio values in most of the soils were >15% indicating very high vulnerability to erosion. The values of clay ratio (3.44–9), modified clay ratio (mean value of 6.9) and critical level of soil organic matter content (<5%) indicated high susceptibility to erosion. The trends of indices were generated by IDW interpolation method to understand the spatial variation of the susceptibility toerosion. The interpolated maps were overlaid on subwatershed maps to prioritize the subwatershed for planning treatment measures.

• Slope failure susceptibility zonation using integrated remote sensing and GIS techniques: A case study over Jhingurdah open pit coal mine, Singrauli coalfield, India

The susceptibility of slopes in open pit coal mines to various modes of failure (i.e., plane, wedge, circular and toppling failure) could be envisaged by virtue of processing and analysis of pertinent satellite data. The aim of the present study was to integrate thematic maps generated using remote sensing imageprocessing techniques, in order to finally produce slope failure hazard zonation maps in and around Singrauli coalfield, India. The various failure-inducing factors, variables and parameters can be extracted from different satellite data and imageries. The data acquired by different sensors such as TM, ETM+,etc., of LANDSAT series and CARTOSAT of ISRO Bhuvan was used in this study. All these data were subsequently used to create different thematic maps such as slope map, lithological map, land use/land cover map, principal component analysis map, digital elevation model (DEM), etc. An advanced analysis for extraction of lineament attributes was also undertaken.

• Assessment of flood mitigation through riparian detention in response to a changing climate–a case study

Considering that urban areas may suffer more substantial losses than riparian farmlands during floods, diverting floodwater into riparian areas for temporal detention is expected to mitigate flood damage in downstream urban areas. In this study, an assessment has been conducted to evaluate the effect of floodmitigation through riparian detention in response to a changing climate in the Tou-Chien River basin of Taiwan. An integrated 1D–2D flow model was used to simulate the movement of flood wave in the main stream and the overbank flow inundating into the nearby lowlands. Based on the numerical simulation results, the flooding extents in the basin corresponding to different return periods of flood using existing flood prevention infrastructures were investigated. A detention strategy by lowering the levee along the riparian farmlands was proposed to avoid severe flooding in the densely populated urban areas of the basin. Research findings showed that the proposed detention measure can completely protect thedownstream areas from overbank flooding when a flood having 20-yr period occurs, and can effectively alleviate the downstream flooding area from 27.4 to $\rm{7.6 km^{2}}$ for a flood possessing 200-yr period.

• Sunspot cycle prediction using multivariate regression and binary mixture of Laplace distribution model

Prediction of sunspot cycle is a vital activity in space mission planning and various engineering decision making. In the present study, the sunspot cycle prediction has been carried out by a hybrid model which employs multivariate regression technique and the binary mixture of Laplace distribution (BMLD) function. The Expectation Maximization (EM) algorithm is being applied to the multivariate regression analysis to obtain a robust prediction of the sunspot cycle. Sunspot cycle 24 has been predicted using this technique. Multivariate regression model has been derived based on the available cycles 1 to 23. This model could predict cycle 24 as an average of previous cycles. Prediction from this model has been refined to capture the cycle characteristics such as bimodal peak at the high solar activity period by incorporating a predicted peak sunspot number from the BMLD model. This revised prediction has shown more accuracy in forecasting the major discrete features of sunspot cycle like maximum amplitude, the Gnevyshev gap, time duration from peak to peak amplitude, and the epoch of peak amplitude. Thisrefined prediction shows that cycle 24 will be having a peak amplitude of 78 with an uncertainty of ±25. Moreover, the present forecast says that, cycle 24 will be having double peak with a strong second peak compared to the first peak. This hypothesis is found to be true with the realized data of cycle 24. Further, this techniques have been validated by predicting sunspot cycles 22 and 23. A preliminary level prediction of sunspot cycle 25 also been carried out using the technique presented here. Present study predicts that, cycle 25 also will be a modest cycle like the present cycle 24, and the peak amplitude may vary in a band of 75–95.

• Significance of assimilation and fractional crystallization (AFC) process in the generation of basaltic lava flows from Chhotaudepur area, Deccan Large Igneous Province, NW India

Basaltic and basaltic andesitic flows have been identified from the Chhotaudepur area in the Deccan Large Igneous Province. The $\rm{SiO_{2}}$ content of these flows varies from 46.7 to 53.7 wt%. None of the samples have primary magma signatures as they exhibit low Mg# (0.42–0.68), Ni (4.8–33.4 ppm) andCr (33.08–143.06 ppm). Highly variable concentrations of the LILE [Rb (2–74 ppm), Ba (52–351 ppm), Cs (0.1–1 ppm) and Sr (273–745 ppm)] and relatively enriched LREE are also noticed. The coherent chondrite normalized REE diagram and primitive mantle normalized multi-element diagram suggests a consanguinity among the flows. Low $\rm{(Nb/Th)_{PM}}$ (0.30–1.09), high $\rm{(Th/Yb)_{PM}}$ (3.09–16.58) ratios and marked variations in Rb concentration (2.4–74.11 ppm) with variable La/Yb (5.5–23.7) ratios suggests that magmas in the Chhotaudepur region were assimilated by the crustal components. The elevated Th/Ta and La/Yb relation further indicate concurrent assimilation and fractional crystallization process was involved in the genesis of the flows. Assimilation and fractional crystallization modelling of the flows was carried out with 20% olivine, 25% clinopyroxene, 45% plagioclase and 10% titano-magnetite as fractionating minerals and upper continental crust as the assimilant. The results reveal that all the flows were modified by AFC process.

• Application of physiographic soil erosion–deposition model in estimating sediment flushing efficiency of empty storage

In this study, we developed a physiographic soil erosion–deposition model to simulate sediment yield from a watershed into Agongdian reservoir and sediment flushing to estimate the efficiency of empty flushing. The model was verified using data related to Typhoons Morakot and Fanapi. Thereafter, we calculated the sediment flushing efficiency of empty storage under the conditions of 1- and 2-day storms with seven return periods. The simulated results revealed that the amount of sediment yield from Joushui River watershed was approximately 70% on average, whereas that from Wanglai River watershed was approximately 30%. These results are consistent with those of a government research report, whichsuggested that the sediment yield figures from Joushui and Wanglai River watersheds were 72 and 28%, respectively. Furthermore, the efficiency of empty flushing was more than 55% when using the shaft spillway pipe, suggesting that the model can be applied to estimate sediment yield and flushing efficiency.

• Geology and tectonic implications of tourmaline bearing leucogranite of Bastipadu, Kurnool, Andhra Pradesh, India

Tourmaline bearing leucogranite occurs as a pluton with pegmatitic veins intruding the Archaean granodiorite in the Bastipadu area, Kurnool district of Andhra Pradesh. We present field and petrographic relations, mineral chemistry and geochemical data for the leucogranite. It is essentially a two-mica granite, composed of quartz, perthite, microcline, albite, tourmaline and muscovite alongwith minor biotite and titanite. The euhedral tourmalines are regularly distributed in the rock. The geochemical studies show that the leucogranite is calc-alkaline, peraluminous to metaluminous which formed in a syn-collisional to volcanic arc-related setting. It displays strong ‘S’ type signatures with high K/Na ratios, moderately fractionated light rare earth elements, relatively flat heavy rare earth elements with $\rm{[Ce/Yb]_{N}} \leq 27.8$ and a strong negative Eu anomaly. The geochemical characteristics indicate that the leucogranite melt might have been generated from partial melting of metasediments. Electron probe microanalyser data show the presence of alkali group tourmaline in leucogranite represented by schorl and dravite. Tourmaline compositions plot in the Li-poor granitoids and associated pegmatites and aplites and metapelites/metasammites fields. Partial melting of boron-enriched source rocks is linked with the development of tourmalines in the leucogranite.

• Structures and morphotectonic evolution of the frontal fold–thrust belt, Kameng river section, Arunachal Himalaya, India

The Neogene–Quaternary Siwalik foreland fold and thrust belt is studied for better understanding of tectonics along the Kameng river section of Arunachal Pradesh, India. The Kimi, Dafla, Subansiri, and the Kimin Formation correspond to Lower, Middle and Upper Siwaliks, respectively. The lithology in the foreland basin is dominantly sandstones, siltstones, claystones, carbonaceous shales, and boulder beds in the upper part. The structural style of the sedimentary sequence from the Main Boundary Thrust southward shows first order ramp-flat geometry. The brittle shear transfers slip across glide horizons to shallower depth. Repeated splay generations from a major regional-scale floor transfers slip from one glidehorizon to another that shortens and thickens the crust. In the micro-scale, the lithological response in the structural development is well documented as pressure solution seams and other diagenetic deformation signatures. The basement asperity plays a significant role as the moving thrust front produced a majorlateral ramp. The differential movement of the mountain front on both sides of the ramp is decipherable. This is especially true at the western part of the SE flowing Kameng river. The tectonic evolution of the area initiated with slip along the MBT $\sim11 \rm{Ma}$ ago along with the deposition of the Siwalik sediments. With southward propagation of the mountain front, the foreland basin shifted towards S, produced splay thrusts from the Himalayan Frontal Thrust-1 (HFT-1), which has been uplifting the Kimin and the older terraces.

• Interpretation of magnetic fabrics in the Dalma volcanic rocks and associated meta-sediments of the Singhbhum Mobile Belt

The present work deals with the generations of Fe–Ti oxides and the variation in magnetic fabrics of the Dalma lavas and associated meta-sediments of the Singhbhum Mobile Belt (SMB) in relation to tectonics. Generations of the Fe–Ti oxides are different in meta-sediments and volcanics, the former preserving upliftment related oxidised grains, whereas the latter contains fresh grains prompting towards their upliftment due to plume upwelling before the volcanic eruption. In the meta-sediments, the magnetic fabric has close accordance with $\rm{D_{2}/F_{2}}$ event revealing synchronous development with $\rm{D_{2}}$. The Dalma thrust developed a sudden break in the homogeneity of the magnetic fabrics of the rocks where the magnetic foliations are all parallel to the Dalma thrust. This also causes P_{j} to be highest in this sector. The magnetic fabrics of volcanic rocks are different from the meta-sediments and record no signature of deformation. The pattern of distribution of susceptibility axes are in accordance with the subaerial lava flows. However, their $\rm{K_{1}}$ and $\rm{K_{2}}$ dispersed throughout the periphery with $\rm{K_{3}}$ clustering at the centre. This infers towards the fact that although the volcanism took place in a subaerial environment, calm aqueous environment was locally present where the oblate grains settled on the eruption surface with their $\rm{K_{3}}$ vertical.

• Petrography and geochemistry of the Proterozoic sandstones of Somanpalli Group from Pomburna area, Eastern Belt of Pranhita–Godavari Valley, central India: Implications for provenance, weathering and tectonic setting

In this paper, we, for the first time, report geochemistry of sandstone from Somanpalli Group from Pomburna area in the Eastern Belt of Pranhita–Godavari (PG) Valley, central India and studied to infer their provenance, intensity of paleo-weathering and depositional tectonic setting. Petrographic study of sandstones show QFL modal composition of arenite. Chemical results show high $\rm{SiO_{2}}$ and CIA but lower $\rm{Al_{2}O_{3}}$, $\rm{TiO_{2}}$, Rb, Sr, $\rm{K_{2}O}$ indicating mixed sources. Major elements chemistry parameters such as, $\rm{K_{2}O/Al_{2}O_{3}}$ ratio and positive correlation of Rb with $\rm{K_{2}O}$, reflects a warm and humid climate for study area. The tectonic discrimination plots $\rm{(SiO_{2}/20–K_{2}O+Na_{2}O–TiO_{2}+Fe_{2}O_{3}+MgO}$; $\rm{K_{2}O/Na_{2}O}$ vs. $\rm{SiO_{2}}$; Th–Sc–Zr/20) indicate dominantly passive margin and slight active tectonic setting. Concentrations of Zr, Nb, Y, and Th are higher compared to the UCC values and the trends in Th/Cr, Th/Co, La/Sc and Cr/Zr ratios support a felsic and mafic source for these sandstones and deposition in passive margin basin. Chondrite normalized REE pattern reflects LREE depletion, negative Eu anomaly and flat HREE similar to UCC, felsic components. ICV value (0.95) also supports tectonically quiescent passive margin settings. CIA values (74) indicate high degree of chemical weathering and warm and humid paleoclimatic condition.

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