Distribution of diagenetic alterations within depositional facies and sequence stratigraphic framework of fluvial sandstones: Evidence from the Petrohan Terrigenous Group,Lower Triassic,NW Bulgaria

Sequence stratigraphy of fluvial deposits is a controversial topic because changes in relative sea level will eventually have indirect impact on the spatial and temporal distribution of depositional facies. Changes in the relative sea level may influence the accommodation space in fluvial plains, and hence have impact on types of fluvial system, frequency of avulsion, and style of vertical and lateral accretion. This study aims to investigate whether depositional facies and changes in the fluvial system of the Lower Triassic Petrohan Terrigenous Group sandstones (NW Bulgaria) in response to changes in the relative sea level have an impact on the spatial and temporal distribution of diagenetic alterations.     

利用SRTM绘制东Sahara大型古排水盆地及其对南埃及新发展计划的影响(英文)

In the current study, the shuttle radar topography mission (SRTM) data, with～90 m horizontal resolution, were used to delineate the paleodrainage system and their mega basin extent in the East Sahara area. One mega-drainage basin has been detected, covering an area of 256 000 km2. It is classified into two sub mega basins. The Uweinate sub mega basin, which is composed of four main tributaries, collected water from a vast catchment region and drained eastward from the north, west, and southwest, starting at...     

Thrust tectonics along the north-western continental margin of Sabah/Borneo

Widely accepted plate tectonic models suggest that an inactive subduction zone lies along the north-west continental margin of Sabah. In contrast, interpretation of reflection seismic data acquired by BGR shows an autochthonous continental terrane comprising an Oligocene to Early Miocene carbonate platform being progressively overthrust by an allochthonous rock complex. Progressive compression resulted in the development of four structural zones: Imbricated thrust sheets (Zone III); two thrust sheet systems one on top of the other (Zone IV); a complex zone with multiphase deformation (Zone V); and piercement ridges (Zone VI).

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Zusammenfassung Nach herkömmlichen plattentektonischen Vorstellungen soll eine inaktive Subduktionszone am nordwestlichen Kontinentalrand von Sabah liegen. Reflexionsseismische Meßdaten der BGR zeigen jedoch, daß hier autochthone kontinentale Kruste mit einer oligozänen-frühmiozänen Karbonatplattform progressiv von einem allochthonen Gesteinsverband überschoben wird. Fortschreitender Zusammenschub seit dem frühen Miozän führte zur Anlage von vier Deformationszonen: Tekonische Schuppen (Zone III); zwei übereinander geschobene Verschuppungssysteme (Zone IV); Gürtel mit mehrphasiger Deformation (Zone V) und Durchspießungsstrukturen (Zone VI).

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Résumé Les modèles géodynamiques que l'on admet habituellement comportent une zone de subduction inactive le long de la marge continentale nord-occidentale de Sabah. Toutefois, des mesures de sismique-réflexion exécutées par le BGR font apparaître qu'à cet endroit, une croûte continentale autochtone, comportant une plateforme carbonatée oligocène à éomiocène, est chevauchée progressivement par un complexe allochtone. La compression, qui s'est manifestée progressivement depuis le Miocène inférieur, a engendré quatre zones structurales: un ensemble d'écailles tectoniques (zone III); deux systèmes de lames tectoniques charriés l'un sur l'autre (zone IV); une zone complexe à déformation multiphasée (zone V); des structures d'extrusion tectonique (zone VI).

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, - Sabah'a. , - . 4-? : ( 3), ( 4) ( 5) ( 6).

     

Evaporitic sedimentation and microbial mats in a salina system (Port Fouad,Egypt)

A salina system along the Mediterranean coast of Egypt was investigated. Five sedimentary facies are described. For each facies, the evaporitic sedimentation and the biological conditions are considered. Comparisons of evaporite precipitates in the salina with ancient deposits are made.     

Microseismicity and tectonics of Sinai

Five microearthquake seismographs were used at 11 sites in northern Sinai in the period February 1987 to February 1988 to study the microseismicity of the area around the Maghara coal mine for mine-development studies. A total of 270 events were recorded on 850 records. The magnitude, epicenter and depth of each event were calculated using suitable software for an Egyptian Geological Survey and Mining Authority's (EGSMA) XT computer. The interpretation of the seismic activity in the area is given in view of plate tectonics, the Sinai subplate boundary follows the Gulf of Aqaba and the Dead Sea. The plate and subplate boundaries are presently active, and there seems to be a diffuse zone of deformation between “NW Africa” and “Nubia” affecting the Cairo-Suez district.     

On the modification of the dynamics in the environment of severe thunderstorms

Summary A detailed study of widespread thunderstorm activity occurring in winter over the central and coastal parts of Egypt (Cairo 30° N, Marsa Matruh 31° N) is presented. The storm activity is associated with strong positive vorticity in the 300/200 mb layer. The maximum kinetic energy was located at the storm centre. The divergent wind component was found to be very important in energy transformation and a major cause of energy generation by cross contour flow.With 3 Figures     

Engineering geology of Mokattam city and vicinity, eastern Greater Cairo, Egypt

A highly jointed, highly fossiliferous, vuggy and sandy dolomitic limestone, the Ain Musa Bed, is the foundation bed rock of Mokattam city. The slopes southwestern sides of the Upper Plateau of Gebel Mokattam, where the city was built, have been affected by slope failure and retreat of the edge of the and a road have been damaged. A 55 m slope retreat took place between 1956 and 1989. A field model is proposed for the slope failure in this area where foundation bed rock are removed by erosion after swelling and flowing, which is due to saturation by leaking fresh and sewage water. The resulting unde bed rock leads to slope failure of large blocks where vertical joints act as potential failure surfaces. Several recommendations are proposed to decrea failure in the city.

The Upper Plateau of Gebel Mokattam is underlain by limestones of the Middle Plateau where a new suburb is being built. A comparison between the geolog properties of the foundation bed rocks of the Upper and Middle Plateaux indicates that the limestones of the latter are more suitable foundation bed ro with expansive clays and are composed of hard, micritic limestones with a few megafossils and no cavities. Rock mass properties are also different and are stable.     

Generation and migration: Identity crisis and political change among the Moro of the Nuba mountains

During the past half century Moro society has undergone immense economic and social transformations. The Moro adopted rural-urban and rural-rural migration, among other things, to diversify their incomes and augment their sources of livelihood. Politically, the introduction of modern political parties since independence in 1956 and the emergence of regional movements have influenced Moro perception of their reality and relationship with their Hawazma and Jellaba neighbours.I argue in this paper that due to disappointments emanating from harsh living conditions in discordant Northern Sudanese towns, the Moro translate past experiences into a common identity. Migration, in this sense, is seen as a major factor in explaining the Moro crisis of identity and their oscillation between integration and aloofness or modernity and traditionalism.     

Availability,affordability and accessibility of food in Khartoum

The failure of some individuals and groups to command adequate food can be accounted for through the analysis of the interplay of three mechanisms, namely food availability, food affordability and food accessibility. In Khartoum, as the case is in many other state-capitals, availability of food is not a major constraint in the dynamics of the food system. Of more significance for the configuration of the space of vulnerability are the processes related to affordability and accessibility, which combine to configurate the space of vulnerability. Occupation, place of residence, ethnic belonging and, of late, political allegiance define to a large extent the location of people in this space.     

Geomorphology and sedimentary/biosedimentary structures of the intertidal environment along the coast of Kuwait,north-western Arabian Gulf

The coast of Kuwait can be divided into nine intertidal geomorphological subunits, of which four are found along the northern muddy shoreline and five along the southern sandy shoreline. In the north the coast is characterized by wide intertidal mudflats, bounded landward by an extensive coastal sabkha which is partly covered by sand drifts. The upper part of the intertidal environment is covered with a mixture of aeolian sands and muddy sediments of marine origin. A number of shallow tidal channels dissect the intertidal flats and small sand bars occur near the low water line. In contrast, the southern shore is characterized by relatively steep sandy beaches fronted by narrow to moderately wide rocky intertidal platforms which are partly covered by sand, bioherms, skeletal debris and algal mats. In some areas the rocky surface is dissected by numerous small gulleys and shallow channels. Multiple sand bars lying either parallel or diagonal to the shoreline are developed near the low water line. This southern intertidal environment is bounded landward by a sandy berm and a wave-cut cliff.Ripple marks are developed almost parallel to the shoreline, showing different flow directions. Energy levels are moderate to high along the southern shore, but low along the northern shore. In the south, waves induced by winds blowing mostly from the north-east and south-east form the dominant energy source, whereas tidal and wind-driven currents are the only tangible process acting along the northern shore.