Geotechnical and geophysical characterization of the Bouira-Algiers Highway (Ain Turck,Algeria) landslide

The Ain Turck (Bouira) landslide, in north-center Algeria, is one of the numerous instabilities recorded along the Lakhdaria-Bouira section of the 1200-km-long east-west Algerian highway. The locality of Ain Turck is known for its unstable slopes characterized by a very rough morphology with steep slopes (20 to 25%). This slide threatens the inhabitants of the Ibournanen village, located down the unstable slope, where parts of some houses have fallen into ruin, while others are cracked. It is characterized by an active movement extending over a more or less important slope, of the order of a hundred meters. The land mobilized by this movement corresponds to the layer of shale clays and clays overlaid by a backfill, placed there following the east-west highway works. Geological, geomorphologic, and geotechnical analysis allows determining the soil instability probably related to earthworks during the construction of the highway section a few years earlier, followed by a particularly rainy season in 2012. Acquisitions of ambient seismic noise and H/V ratio processing, as well as the acquisition of an electrical resistivity profile at the instability site, have reinforced our preliminary interpretations of depth and geometry of the sliding surface.     

Variographic analysis of water table data from the Oued-Souf phreatic aquifer, northeastern part of the Algerian Sahara

Phreatic aquifers present many serious problems for local public authorities, and they have done so especially for the water resources managers in Oued-Souf, Algeria, since 1980. Recently, a perturbation in piezometric level was observed in Oued-Souf. The spatial distribution of piezometric level data was analyzed by applying geostatistical methods, which provide an indication of the uncertainty of the estimation using the computer software VARIOWIN 2.2. In this paper, the evolution of the piezometric level by referring to other research campaigns was studied. Campaigns were conducted from March 1993 to April 2002. In the beginning, elementary statistics has been carried out to understand the statistical distribution and performed an analysis of variance so that two campaigns could be chosen for comparison. Geostatistics for modeling and cartography were applied. The results show that piezometric levels admit power model that the direction of groundwater flow is from south to north and that, due to the return of irrigation water (there is no drainage system), water levels increase in places like Foulia (1.35 m), northwest of Oued-Souf (1.43 m), Kouinine (4.58 m), and Ouzitene (3.01 m). The water levels also decrease in places like Guemar, Dmitha, Rhamra, and Djeldida, from between −2 and −6 m, due to excessive pumping of groundwater.     

Tectonic and magmatic evolution of the eastern Karakoram,India

Abstract

The Shyok suture zone separates the Ladakh terrane to the SW from the Karakoram terrane to the NE. Six tectonic units have been distinguished. From south to north these are; 1. Saltoro formation; 2. Shyok volcanites; 3. Saltoro molasse; 4. Ophiolitic melange; 5. Tirit granitoids; 6. Karakoram terrane including the Karakoram batholith. Albian—Aptian Orbitolina-bearing lime-stones and turbidites of the Saltoro formation tectonically overlie high-Mg-tholeiites similar to the tectonically overlying Shyok volcanites. The high-Mg tholeiitic basalts and calcalkaline andesites of the Shyok volcanites show an active margin signature. The Saltoro molasse is an apron-like, moderately folded association of redgreen shales and sandstones that are interbedded with ~ 50 m porphyritic andesite. Desiccation cracks and rain-drop imprints indicate deposition in a subaerial fluvial environment. Rudist fragments from a polygenic conglomerate of the Saltoro molasse document a post-Middle Cretaceous age. The calcalkaline andesites of the Shyok volcanites are intruded by the Tirit granitoids, which are located immediately south of the Ophiolitic melange and belong to a weakly deformed trondhjemite-tonalite-granodiorite-granite suite. These granitoids are subalkaline, I-type and were emplaced in a volcanic arc setting. The subalkaline to calcalkaline granitoids of the Karakoram batholith are I-and S-type granitoid. The I-type granitoids represent a typical calcalkaline magmatism of a subduction zone environment whereas the S-type granitoids are crustderived, anatectic peraluminous granites. New data suggest that the volcano-plutonic and sedimentary successions of the Shyok suture zone exposed in northern Ladakh are equivalent to the successions exposed along the Northern suture in Kohistan. It is likely that the o istan and Ladakh blocks evolved as one single tectonic domain uring the Cretaceous-Palaeogene. Subsequently, collision, suturing and accretion of the Indian plate along the Indus suture (50–60 Ma) together with tectonic activity along the Nanga Parbataramosh divided Kohistan and Ladakh into two arealy distinct magmatic arc terranes. The activity and a dextral offset along the Karakoram fault (Holocene-Recent) disrupted the original tectonic relationships. © 1999 Éditions scientifiques et médicales Elsevier SAS     

Diagenetic evolution of the volcaniclastic deposits: an example from Neoproterozoic Dokhan Volcanics in Wadi Queih basin,central Eastern Desert,Egypt

Wadi Queih basin hosts a ～2,500-m thick Neoproterozoic volcanoclastic successions that unconformably lie over the oldest Precambrian basement. These successions were deposited in alluvial fan, fluviatile, lacustrine, and aeolian depositional environments. Diagenetic minerals from these volcaniclastic successions were studied by X-ray diffractometry, scanning electron microscopy, and analytical electron microscopy. The diagenetic processes recognized include mechanical compaction, cementation, and dissolution. Based on the framework grain–cement relationships, precipitation of the early calcite cement was either accompanied or followed by the development of part of the pore-lining and pore-filling clay cements. Secondary porosity development occurred due to partial to complete dissolution of early calcite cement and feldspar grains. In addition to calcite, several different clay minerals including kaolinite, illite, and chlorite with minor smectite occur as pore-filling and pore-lining cements. Chlorite coating grains helps to retain primary porosity by retarding the envelopment of quartz overgrowths. Clay minerals and their diagenetic assemblages has been distinguished between primary volcaniclastics directly produced by pyroclastic eruptions and epiclastic volcaniclastics derived from erosion of the pre-existing volcanic rocks. Phyllosilicates of the epiclastic rocks display wider compositional variations owing to wide variations in the mineralogical and chemical compositions of the parent material. Most of the phyllosilicates (kaolinite, illite, chlorite, mica, and smectite) are inherited minerals derived from the erosion of the volcanic basement complex, which had undergone hydrothermal alteration. Smectites of the epiclastic rocks are beidellite–montmorillonite derived from the altered volcanic materials of the sedimentary environment. Conversely, phyllosilicate minerals of the pyroclastic rocks are dominated by kaolinite, illite, and mica, which were formed by pedogenetic processes through the hydrothermal influence.     

Geochemical and stable isotopic studies of Gulf of Suez’s hot springs, Egypt

The Gulf of Suez region is one of the most interesting geothermal areas in Egypt because of the high temperatures of its springs.The eastern and western shores of the Gulf of Suez are characterized by superficial thermal manifestations including a cluster of hot springs with varied temperatures.Variations of deuterium and oxygen-18 concentrations in thermal waters have been used to aid in describing the source of recharge in the Gulf of Suez hot springs.Isotope and geochemical data for the Gulf of Suez thermal waters suggest that recharge to the hot springs may not be entirely from the Gulf of Suez water,but possibly from the meteoric water that comes from areas of higher altitude surrounding the hot springs.     

Integrated gravity and seismic investigations over the Jebel Es Souda-Hmaeima structure: implication for basement configuration of the eastern frontal fold-and-thrust belt of Tunisian Atlasic Mountains

A gravity and seismic analysis was conducted over and around Jebel Es Souda-Hmaeima, located on the eastern border of the Tunisian Mountains between the Atlasic block to the west and the Pelagian Block to the east, as part of a study to investigate the subsurface structures. These data, together with outcrop geology, well data, and measurements of physical properties of rock samples, were integrated with a new interpretation of the tectonic model of Jebel Es Souda-Hmaeima anticline. This structure represents a backfolded anticline associated with a steep east-vergent thrust above a blind thrust fault along the base of Triassic formations. The proposed model emphasizes the role of transpressional deformation along deep-seated basement faults and has implications for petroleum generation, migration, and entrapment in central Tunisia.     

Characterisation, classification, and evaluation of some groundwater samples in the Mostaganem area of northwestern Algeria

Mostaganem City, located in the northwestern part of Algeria, has grown and has been urbanized rapidly. The city and surrounding areas depend heavily on groundwater as a resource for drinking water, as well as domestic, industrial, and agricultural uses. Understanding the groundwater chemistry provides insight into the interactions of water with the environment and contributes to better resource management. In total, 12 groundwater samples from wells in Mostaganem City have been analyzed for major physical–chemical elements and metals. The results show that the waters have pH values ranging between 7.1 and 8.1, salinity between 226 and 1,073 mg/L, and nitrate concentrations between 15 and 47.7 mg/L. The high concentration of nitrates is explained by the utilization of chemical fertilizers in agriculture. Almost all samples are of type Na–SO₄ and Na–HCO₃, and the trace metal concentrations are within the admissible standard ranges. We conclude that the groundwater in Mostaganem may safely be used for drinking, domestic, agricultural, and industrial purposes.