Ichnology of Bhuban and Boka Bil Formations,oligocene-miocene deposits of Manipur Western Hill,Northeast India

Oligocene-Miocene deposits of Bhuban and Boka Bil Formations, Surma Group, Manipur Western Hill consist of well preserved ichnofossil assemblages. These formations are represented by eight lithofacies such as Massive sandstone (Sm), Rippled marked argillaceous sandstone (Sr), Wavy laminated sandstone-siltstone-silty shale (Sw), Laminated shale (Fl), Massive mudstone (Fm), Trough cross-bedded sandstone (St), Lenticular laminated sandstonesiltstonesilty shale (Sll) and Laminated to massive sandstone-siltstone (Ssc). Fifteen ichnospecies were identified, which further categories into Skolithos, Cruziana, and Skolithos/Cruziana ichnofacies. Overall distribution pattern and behavioural nature of the ichnoassemblage and sedimentological attributes suggests that the sediments of Bhuban and Boka Bil Formations were deposited under frequent fluctuating sea level, moderate to strong energy condition, subtidal to lower intertidal environment, rich in organic nutrients.     

Geomorphic characteristics of a bedrock river inferred from drainage quantification,longitudinal profile,knickzone identification and concavity analysis: a DEM-based study

An examination of river channels has ability to provide substantial information regarding the geomorphic characteristics, control of lithology, tectonic uplift and geomorphic evolution during the geological past of an area. In this paper, a detailed study of geomorphic and structural investigation has been carried out for Pravara basin, Maharashtra, with the help of 90-m resolution SRTM DEM and geospatial techniques. Drainage network analysis performed in this paper demonstrates the general geomorphic characteristics, while the analysis of longitudinal profile synthesises lithological control over Pravara basin. Pravara is a 6th order drainage basin, encompassing an area of 2637 km². Bifurcation ratio reveals low to moderate structural control. Due to the hard rock lithology, the drainage density and stream frequency are low, and it indicates higher permeability in the sub-surface layers. The shape parameters denote that Pravara is highly elongated and it is easier to control floods in this basin. Relief parameters show very steep slope and higher vulnerability to the slope failure in some areas. Upstream of Pravara river has shown that series of breaks and knickzones indicate active erosion and acute lithological control on the channel. Major breaks are observed only in the main channel whereas in two major tributaries, no such breaks found, instead these tributaries are characterised by several knickzones which indicate regional variation in the lithological physiognomies. Different lithological stages on knickpoint and channel incision substantiate rejuvenation of Pravara river in several phases during geological past. The geospatial methodology carried out in this study can be pragmatic elsewhere around this world to recognise the geomorphic appearances and lithological control of a drainage basin.     

Monitoring of fire incidences in vegetation types and Protected Areas of India: Implications on carbon emissions

Carbon emissions released from forest fires have been identified as an environmental issue in the context of global warming. This study provides data on spatial and temporal patterns of fire incidences, burnt area and carbon emissions covering natural vegetation types (forest, scrub and grassland) and Protected Areas of India. The total area affected by fire in the forest, scrub and grasslands have been estimated as 48765.45, 6540.97 and 1821.33 km ², respectively, in 2014 using Resourcesat-2 AWiFS data. The total CO ₂ emissions from fires of these vegetation types in India were estimated to be 98.11 Tg during 2014. The highest emissions were caused by dry deciduous forests, followed by moist deciduous forests. The fire season typically occurs in February, March, April and May in different parts of India. Monthly CO ₂ emissions from fires for different vegetation types have been calculated for February, March, April and May and estimated as 2.26, 33.53, 32.15 and 30.17 Tg, respectively. Protected Areas represent 11.46% of the total natural vegetation cover of India. Analysis of fire occurrences over a 10-year period with two types of sensor data, i.e., AWiFS and MODIS, have found fires in 281 (out of 614) Protected Areas of India. About 16.78 Tg of CO ₂ emissions were estimated in Protected Areas in 2014. The natural vegetation types of Protected Areas have contributed for burnt area of 17.3% and CO ₂ emissions of 17.1% as compared to total natural vegetation burnt area and emissions in India in 2014. 9.4% of the total vegetation in the Protected Areas was burnt in 2014. Our results suggest that Protected Areas have to be considered for strict fire management as an effective strategy for mitigating climate change and biodiversity conservation.     

Über Sedimentbildung am Meeresboden

Ohne Zusammenfassung     

Eine statistische Theorie der Böigkeit des Windes

Zusammenfassung Es werden Gleichungen abgeleitet, mittels derer man aus dem Energiespektrum des Windes die Häufigkeit von Böen bestimmter Größe und bestimmter Mindestgröße, die Größe der häufigsten Böenspitze und einen mittleren Abstand zwischen zwei Böenstößen berechnen kann. Die Theorie wird an einem Beispiel erläutert.

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Summary Equations are derived which allow the calculation of frequencies of gusts with a velocity equal or larger than a given amount, of the velocity of the most frequent gust, and of a mean interval between two gusts out of the power-spectrum of wind. The theory is illustrated by an example.

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Résumé L'auteur établit des formules permettant de calculer les grandeurs suivantes en partant du spectre énergétique du vent: Fréquence des rafales de force ou de force maximale déterminées, force des rafales les plus fréquentes ainsi que le temps moyen séparant deux rafales. Il démontre sa théorie par un exemple.

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Mit 4 Textabbildungen     

Weak GPS signal tracking using FFT discriminator in open loop receiver

An open loop tracking architecture, which tracks GPS signals under weak and challenging conditions, is analyzed. The in-phase and quadrature-phase integration pair is regarded as a single tone complex signal. An FFT-based method is used as a frequency discriminator to estimate the Doppler frequency residual of the single tone signal. Another FFT-based method applies complex squaring to eliminate the effect of the navigation data bits polarities. The performance of the FFT-based discriminators is assessed in three criteria. Those criteria are the signal strength and dynamic range that can be tracked and the accuracy of the estimated Doppler frequency. In addition, the performance of the discriminators is analyzed to provide the theoretical and simulated peak detection probability. The results indicate that the FFT discriminator can track signals about 5 dB weaker than the signals that can be tracked by the complex squared FFT discriminator. In a quasi-static environment, the Doppler frequency residual can be assumed to be around zero, which can enable the FFT-based discriminators to track signals with approximately 2 dB less power. Moreover, the performance of the FFT-based discriminators is compared with the performance of two other frequency discriminators, namely the fast–slow and power-based. The comparison results indicate that these two frequency discriminators give higher frequency estimation accuracy, but they have a narrower dynamic range.     

Seismic profile analysis of the Kangra and Dehradun re-entrant of NW Himalayan Foreland thrust belt,India: A new approach to delineate subsurface geometry

In the NW Sub-Himalayan frontal thrust belt in India, seismic interpretation of subsurface geometry of the Kangra and Dehradun re-entrant mismatch with the previously proposed models. These procedures lack direct quantitative measurement on the seismic profile required for subsurface structural architecture. Here we use a predictive angular function for establishing quantitative geometric relationships between fault and fold shapes with ‘Distance–displacement method’ (D–d method). It is a prognostic straightforward mechanism to probe the possible structural network from a seismic profile. Two seismic profiles Kangra-2 and Kangra-4 of Kangra re-entrant, Himachal Pradesh (India), are investigated for the fault-related folds associated with the Balh and Paror anticlines. For Paror anticline, the final cut-off angle \(\beta =35{^{\circ }}\) was obtained by transforming the seismic time profile into depth profile to corroborate the interpreted structures. Also, the estimated shortening along the Jawalamukhi Thrust and Jhor Fault, lying between the Himalayan Frontal Thrust (HFT) and the Main Boundary Thrust (MBT) in the frontal fold-thrust belt, were found to be 6.06 and 0.25 km, respectively. Lastly, the geometric method of fold-fault relationship has been exercised to document the existence of a fault-bend fold above the Himalayan Frontal Thrust (HFT). Measurement of shortening along the fault plane is employed as an ancillary tool to prove the multi-bending geometry of the blind thrust of the Dehradun re-entrant.     

Experimental study on the instability mechanism of the major-defect fractured rock

Based on calculations of rock fracture surface and angle, incremental-load creep experiments were conducted on two groups of major-defect fractured rock specimens in an RLW-2000 rheology test system. The research investigated the fracture type and the creep properties of major-defect fractured rock and analyzed the relationships between failure load and horizontal or vertical projection distance, and between each of theme and fracture area or angle. The results showed that rock fracture was divided into three types according to the distribution, including I, II, and III types. I, II, and III types were respectively an internal fracture running through neither the upper nor lower end, one through the upper or lower end and one through both upper and lower ends, and a III type was further sub-divided into III_I and III_II types. The instantaneous strain was larger than the creep strain under the same creep loading stage. As the creep loading increased on two groups of major-defect fractured rock, the instantaneous strain decreased abruptly and then increased abruptly, while the creep strain decreased rapidly at first and later increased near-linearly. When the failure angle was larger than the friction angle, failure load was positively correlated with failure angle yet was negatively correlated with vertical projection distance. Vertical projection distance and fracture angle, which decided fracture type, controlled rock failure load. Failure load increased in turn from I type to III type, and low-type fracture determined mainly failure load in multiply-fracture specimen.     

Wavefield analysis of crosswell seismic data

Despite the numerous advantages of crosswell seismic data over surface seismic data, crosswell seismic geophysics is still underutilized and underdeveloped. The factors limiting the full utilization of crosswell data include the lack of standardized methods for processing and imaging the data. This is because crosswell data is not completely understood. To improve the understanding of crosswell data, we performed acoustic and elastic modeling of a west Texas carbonate oilfield data using finite difference methods and crosswell geometry. To account for the different wave modes in the field data, we decomposed the full data into its constituent wave modes. Results of the forward modeling show that elastic synthetic data is a better representation of crosswell field data than the popular acoustic synthetic data. Wavefield decomposition gave insight into the time-space kinematics behavior of the different wave modes that constitute the full data. Overall, the study improved our understanding of crosswell field data. The learning from this study has been utilized to perform data-driven reflection enhancement processing where the discerned characteristic of different seismic arrival is utilize to suppress unwanted and enhanced the desired wave modes. The processing reduced the complex data to only up-going P-P reflections that can be imaged to reveal the subtle geological structures of the oilfield.