Use of remote sensing in lineament analysis for tectonic evolution and resource study of a part of Vindhyan Basin,Jhalawar area,India

Synoptivity and the exemplified fracture systems exhibited by the space borne imagery data has helped in solving many of the geological enigma in various parts of the world. The study conducted, using such remotly sensed data, in Jhalawar anticline, part of Proterozoic Cratonic Vindhyan Basin, Rajasthan, India, led to infer the history of tectonic evolution of peribasinal deformation which has been a matter of controversy for a century and more. In Landsat MSS data the Jhalawar region displays a panorama of lineaments and their analysis through azimuthal frequency diagrams, isofracture, lineament incidence and lineament intersection incidence density maps shows that the mean orientation of the lineaments fall in NW-SE and NE-SW and the shape of the various lineament density contours also show NE-SW and NW-SE orientations. In aerial photographs the area exhibits four sets of lineaments in NE-SW, NW-SE, N-S and E-W directions. Amongst these the former two sets are expressed as wide open master fracture systems with prolific vegetation fills along them and the latter two sets are characteristically observed as thin vegetation linears with frequent strike slip faulting along them. The further analysis of these fracture/lineament systems derived from multi-level remote sensing data shows that the Jhalawar anticline, which followed the pattern of flexural slip fold mechanism, was evolved by horizontally disposed σ1 (greatest principal stress) and 3σ (least principal stress) with the former oriented in NE-SW and the latter aligned in NW-SE directions with vertically disposed 2σ. The inference of such palaeostress environment of the Jhalawar region lead in the identification of a buried rigid basement high southwest of Jhalawar anticline, beneath the Deccan pile and loci of ground water, silica sand and probable igneous plug.     

Geodynamic evolution of the lithosphere of the Sea of Okhotsk region from geophysical data

The tectonic structure and anomalous distributions of geophysical fields of the Sea of Okhotsk region are considered; the lack of reliable data on the age of the lithosphere beneath basins of various origins in the Sea of Okhotsk is noted. Model calculations based on geological and geophysical data yielded an age of 65 Ma (the Cretaceous-Paleocene boundary) for the Central Okhotsk rise underlain by the continental lithosphere. This estimate agrees with the age (the end of the Cretaceous) derived from seismostratigraphic data. A comparative analysis of theoretical and measured heat fluxes in the Akademii Nauk Rise, underlain by a thinned continental crust, is performed. The analysis points to a higher (by 20%) value of the measured thermal background of the rise, which is consistent with a high negative gradient of gravity anomalies in this area. Calculations yielded an age of 36 Ma (the Early Oligocene) and a lithosphere thickness of 50 km for the South Okhotsk depression, whose seafloor was formed by processes of backarc spreading. The estimated age of the depression is supported by kinematic data on the region; the calculated thickness of the lithosphere coincides with the value estimated from data of magnetotelluric sounding here. This indicates that the formation time (36 Ma) of the South Okhotsk depression was estimated correctly. Numerical modeling performed for the determination of the basement age of rifting basins in the Sea of Okhotsk gave the following estimates: 18 Ma (the Early Miocene) for the Deryugin basin, 12 Ma (the Middle Miocene) for the TINRO basin, and 23 Ma (the Late Oligocene) for the West Kamchatka trough. These estimates agree with the formation time (Oligocene-Quaternary) of the sedimentary cover in rifting basins of the Sea of Okhotsk derived from geological and geophysical data. Model temperature estimates are obtained for lithologic and stratigraphic boundaries of the sedimentary cover in the Deryugin and TINRO basins and the West Kamchatka trough; the temperature analysis indicates that the latter two structures are promising for oil and hydrocarbon gas generation; the West Kamchatka trough possesses better reservoir properties compared to the TINRO and Deryugin basins. The latter is promising for the generation of hydrocarbon gas. Paleogeodynamic reconstructions of the Sea of Okhotsk region evolution are obtained for times of 90, 66, and 36 Ma on the basis of kinematic, geomagnetic, structural, tectonic, geothermal, and other geological and geophysical data.     

Food gardens as important elements of urban agriculture: Spatio-developmental trends and future prospects for urban gardening in Czechia

The main research goals of the article are to explain the historical context of urban food gardens in Czechia, to describe the current spatial pattern of allotment gardens, and to introduce and analyse recent trends in urban gardening. The main method for achieving the first goal was a literature study. For the second goal, geographical mapping and analysis of data relating to the spatial distribution of allotment gardens were used. For the third goal, mapping together with analysis of semi-structured interviews carried out in community gardens in Prague were used. The analysis showed a strong tradition of urban agriculture and urban food gardening activities in Czechia. Both allotment gardens and newly emerged community gardens were concentrated mainly in the biggest cities and in areas with a rich industrial and mining tradition. This finding supports the significance of gardening as an important element of urban agriculture. However, uncertainty regarding land tenure and long-term sustainability were among the greatest obstacles for the future of allotment and community gardens. The authors’ main recommendations are that urban agriculture should be included as primary land use in sustainable planning and there should be broader community involvement in planning and decision-making processes.     

Stacking of records of nuclear explosions registered by the world network of seismic stations

The methods and results of stacking of seismograms of nuclear explosions registered by the world network of seismic stations from 1980 until 1988 are presented. Stacking of seismograms obtained at one seismic station from the sources located in the same place allows us substantially to increase the useful signal/noise ratio. This, in turn, allows more confident correlation of various seismic waves coming to the seismic stations after the first arrivals, particularly, converted and reflected waves from different boundaries inside the Earth.     

Unusual spatial-temporal dynamics of geomagnetic disturbances during the main phase of the extremely strong magnetic storm of November 7–8, 2004

The spatial dynamics of geomagnetic variations and pulsations, auroras, and riometer absorption during the development of the main phase of the extremely strong magnetic storm of November 7–8, 2004, has been studied. It has been indicated that intense disturbances were observed in the early morning sector of auroral latitudes rather than in the nighttime sector, as usually takes place during magnetic storms. The unusual spatial dynamics was revealed at the beginning of the storm main phase. A rapid poleward expansion of disturbances from geomagnetic latitudes of 65°–66° to 74°–75° and the development of the so-called polar cap substorm with a negative bay amplitude of up to 2500 nT, accompanied by precipitation of energetic electrons (riometer absorption) and generation of Pi2–Pi3 pulsations, were observed when IMF B _z was about ?45 nT. The geomagnetic activity maximum subsequently sharply shifted equatorward to 60°–61°. The spatial dynamics of the westward electrojet, Pi2–Pi3 geomagnetic pulsations, and riometer absorption was similar, which can indicate that the source of these phenomena is common.     

Variations of global water exchange under changing climate

Variations of Global Sea Level are considered as an integral indicator of global water exchange. The results of analysis of Global Sea Level variations over past 140 years are estimated from tide-gauge data. Level trend in the XX century is shown to amount to 1.8 mm/year. The contributions of various factors to the formation of Global Sea Level trend are discussed. The interannual variations of evaporation and precipitation over the World Ocean are estimated for the first time, and their difference is shown to significantly contribute to the level trend, especially in the recent decade. Moreover, the significant rise in Global Sea Level is associated with the thermosteric level variations and, possibly, with the bottom melting of Antarctic shelf glaciers.