Compressibility and swelling characteristics of Al-Khobar Palygorskite, eastern Saudi Arabia

Expansive soils are found in different locations in eastern Saudi Arabia. The area is arid with high temperatures, highly variable humidity and an excessive rate of evaporation compared to the low precipitation. This resulted in the formation of water sensitive soils. In the present investigation, line valve buildings for a sweet water feeder (1118 mm in diameter) were constructed on a highly expansive material consisting mainly of brown palygorskite and gray palygorskite with thin sheets of gypsum and limestone. Block samples from both palygorskites were brought to the laboratory and cores as well as remolded samples were obtained from the blocks. The two palygorskites were found to be highly plastic and have a very high swelling potential. The liquid limit (LL) and plastic limit (PL) values for the brown palygorskite are 261% and 140%, respectively. The gray palygorskite has a LL of a 285% and a PL of 123%. The oedometer free swell tests for the two palygorskites produced an expansion ranging between 31.8% and 42.5% for the remolded samples. However, the expansion for cores ranges between 8.3% and 19.3%. The constant volume pressure tests produced a stress in excess of 4240 kPa. The swell potential reached a steady state after four days while the swelling pressure reached a steady state in about 3 h. The paper addresses the geology of the area, the characterization of the geomaterial including mineralogical composition using X-ray diffraction and SEM techniques and the swelling characteristics of the material.     

Sediment characteristics and molluscan fossils of the Farasan Islands shorelines,southern Red Sea,Saudi Arabia

The Farasan Islands are located about 40 km offshore of Jizan area, southern Red Sea, Saudi Arabia. This is a preliminary study aiming to collect shoreline sediments from 17 stations to describe their main lithologic characters and identify the dominant molluscs that could help to evaluate the environmental conditions of these islands. Also, a sediment core FARA2 was collected from the intertidal area of Khor As Sailah Lagoon to see the development of shoreline sediments in this area with time. The results indicated that the shoreline sediments of the Farasan Islands comprised mainly of white, biogenic sand enriched in remains of corals, molluscs, calcareous algae, and benthic foraminifera. Thirty-four mollusc species were recorded from these sediments. Among them, Strombus fasciatus, Strombus tricornis, Chicoreus ramosus, Chicoreus virgineus, Tridacna maxima, and Tridacna squamosa were the most common molluscan in/near the shoreline sediments of Farasan Islands. Frequency abundances of sediment grain-size fractions in the core FARA2 indicated that the shoreline of the Khor As Sailah Lagoon is developing towards shallow intertidal setting due to high production of biogenic sediments by reefal communities. Metal concentrations (Fe, Mn, Cu, and Zn) in the sediment of the core FARA2 were stable throughout, showing no remarkable changes. This finding could indicate that flux of detrital components by fresh water runoff or wind-blown dust over the Farasan Islands was un-detectable during the deposition of these sediments.     

Regional tectonic and megadepositional cycles of the Paleozoic of northwestern and central Saudi Arabia

The Paleozoic succession of the Greater Arabian basin is severely affected by series of major tectonic and climatic events which have caused major stratigraphic breaks and pronounce facies change. The major tectonic movements have resulted in dividing the succession into pronounced megatectonic and depositional cycles. In more tectonically active areas, the succession is less preserved and boundaries between the cycles are more complicated due to longer periods of erosion by later movements and/or nondeposition. Minor stratigraphic breaks within the megacycles subdivide the cycles into smaller subcycles. Following the stabilization of the Arabian–Nubian shield, the Gondwana shelf went through a gentle uplift and tilt probably related to the Assyniyc tectonic movements and thick siliciclastics of the Saq and Qasim Formations were deposited. During Late Caradocian and following the deposition of the Qasim Formation, the area went through a gentle uplift and tilt probably related to the Taconic tectonic movements. Thick succession of the Qasim and Saq Formations were eroded and deep paleovalleys incised in the two formations and underlying basement. The movements were followed by drop of sea level due to glaciation events. Glacial and periglacial deposits of the Zarqa and/or Sarah Formations filled paleovalleys and rest on older units from Ordovician to Precambrian. The third main event occurred during Late Silurian where the preexisting successions, mainly on paleohighs, were affected by tectonic movements synchronous with the Acadian tectonic phase of the Caledonian tectonic movements. The Early Devonian Tawil Formation unconformably rests on eroded Silurian and Late Ordovician deposits of the Sharawra, Qusayba (Qusaiba), and Sarah Formations in the Qusayba Depression in central Arabia. The forth main event is a regional movement contemporaneous with the Hercynian tectonic movement which has reached its maximum phase in the Late Carboniferous. Earlier successions from Carboniferous to Precambrian were affected and the Permo-Carboniferous Shajra Formation unconformably rests on all underlying Paleozoic rock units toward the central Arabia arch and other paleohighs. The Shajra rests on the Devonian Jawbah (Jubah), Jawf (Jauf) and Tawil formations, the Silurian Sharawra, Qusayba, and Uqlah formations, the Ordovician Zarqa/Sarah, and Qasim formations, the Cambro-Ordovician Saq Formation, and finally rests on Precambrian Basement complex in Central Arabia. The tectonic movements played important role in shaping the structural framework of Arabia. The Paleozoic succession included source, reservoir, and seal rocks. Oil and gas have been discovered in sandstone and limestone reservoirs in these rocks in several oilfields in the basin.     

Holocene shore displacement and shorelines in Hordaland, western Norway

A new shore displacement curve from Fonnes, ca. 50 km NW of Bergen, and a revised curve from Bømlo, ca. 80 km S of Bergen, are presented, based on pollen and phytoplankton analysis of organic sediments in present and ancient lake basins. The transitions between marine and lacustrine sediments have been radiocarbon-dated. The Fonnes and Bømlo curves are closely related and show a rapid regression between 10,000 and 8,700 years B.P., from 30 m above sea level to ca. 4 m above sea level. A transgression took place between 8,500 and 7,200 years B.P. when the shore level rose to ca. 11 m above sea level. Between 7,200 and 6,000 years B.P. the shore level was almost constant, before a slow regression took place. The earlier interpretation of the Tapes transgression including two shore level oscillations at Bømlo is rejected. A method is presented for constructing an equidistant shoreline diagram on the basis of three radiocarbon-dated shore displacement curves from three areas arranged in a triangle (Fonnes, Sotra, Ostereidet). When followed along the projection plane, a working model of the shore displacement curve from Fonnes and an approximation of the change in shoreline gradient during the Holocene indicate that the transgression maximum is metachronous.     

Late Holocene tectonic movements at Akhziv,Mediterranean coastline of northern Israel

The recent discovery of a post-Roman-aged marine calcarenite terrace, at an altitude of 7 to 8 m at the ancient harbor of Akhziv, supports the hypothesis of oscillatory tectonic movements along the coastline of Israel during the late Holocene. The marine to estuarine origin of this terrace is indicated by the presence within it of a biocoenosic, sea-marginal to estuarine, assemblage of well-preserved molluscs consisting of taxa tolerating brackish-water, together with a few fresh-water specimens. The transgressive marine sediments onlap and overlie a 2700-yr-old middle Iron Age (Phoenician) tomb, which was built on a dark clay layer, containing a middle Bronze HB (3750 yr B.P.) settlement. In post-Roman times the coastal zone at this site, both east and west of the present coastline, was first subjected to tectonic subsidence of a few meters, and was then tectonically uplifted to its present altitude.     

The Jinadriyah anticlines: a surface model for oil fields in eastern Saudi Arabia

Mesozoic oil in Saudi Arabia exists in north/south-oriented anticlines. Such anticlines are usually studied using subsurface data. The present study introduces, for the first time in Saudi Arabia, a surface analog for these anticlines. The study covers two northerly oriented anticlines located in the Jinadriyah area at 15 km to the northeast of the Riyadh city. They are named herein the North and South Jinadriyah anticlines. The outcrops in both anticlines belong to the Lower Cretaceous Yamama Formation which consists of limestone in its lower part and limestone with shale in its upper part. The study included initially detailed interpretation of Google Earth and Landsat TM images to map the structural pattern of the anticlines. Detailed field mapping confirmed the satellite image interpretation and helped describe the geometry of the two anticlines in detail. The 3.5-km-long South Jinadriyah anticline is an open doubly plunging asymmetric anticline. The western flank is dissected by 13 minor reverse faults of north–south orientation. The North Jinadriyah anticline is about 5.5 km long and is relatively more complex than the South Jinadriyah anticline. It consists of northern, central, and southern segments that differ from each others in orientation and style. The anticline is dissected by 18 minor faults of different orientations and sense of displacement. Two perpendicular fracture sets with one being parallel to the anticline axes were recorded in the two anticlines. Both anticlines are interpreted as fault-propagation folds that were formed during the Late Cretaceous first Alpine orogeny. The mid-Late Tertiary second Alpine orogeny and Late Tertiary eastward tilting of the Arabian Plate increased the degree of folding and faulting.     

Characterization of Sabkha Jayb Uwayyid, eastern Saudi Arabia using seismic refraction profiling

Sabkhas are dominant geomorphic features in eastern Saudi Arabia and are of geologic and economic significance. Seismic refraction method was used in the inland sabkha of Jayb Uwayyid to depict its general stratigraphy and determine velocities and thicknesses of the sabkha’s uppermost layers and the water table depth. Data were acquired using a reversed-refraction profile consisting of 48 receivers spaced at 5 m. Data processing included amplitude gain, band-pass filtering, and manual picking of first and second arrivals. Interpretation of the data shows three main layers. The first layer is a sandy layer having an average velocity and thickness of 600 m/s and 15 m, respectively. The second layer has an average velocity and thickness of 2,300 m/s and 113 m, respectively. The third layer has an average velocity of 3,850 m/s. The topmost part of the first layer is composed of a dry to partially saturated clean sand underlain by fully saturated clean sand. However, arrivals from the interface between the partially saturated and fully saturated sands were not recognizable in any shot record, which might be due to the gradual increase of saturation with depth. Arrivals from the second layer were always recognizable on all shot records as first arrivals. On the other hand, arrivals from the third layer were not recognizable on any shot record as first arrivals probably due to the limited extent of the profile relative to the depth of the third layer. Therefore, the velocity of the third layer was calculated by manually picking the second head wave arrival.     

Effect of tectonic prominence and growth of the Arabian shield on Paleozoic sandstone successions in Saudi Arabia

Paleozoic successions in Saudi Arabia are exposed around and bordering the south, north, and northeastern edge of the Arabian shield. They are represented by the Wajid group in the south and by the Taymah, Tabuk, Qalibah, Huj, and Buraydah groups in the north and northeast. The Wajid group includes Dibsiyah, Sanamah, Khusayyan, and Juwayl formations. The Taymah group includes Siq, Amai’er, Quweira, Saq, and Qasim formations. The Tabuk group includes Zarqa, Sara, and Hawban formations. The Qalibah group includes Baq’a, Qusaiba, and Sharawra formations. The Huj group includes Tawil, Jauf, and Jubah formations. The Buraydah group includes Berwath, Unayzah, and Khuff formations. The Wajid group form one block in the south and the other groups form another block in the north, and they can be correlated. There are similarities between the northern belt which consists of the Cambro-Ordovician formations of the Tayma and Tabuk groups and the southern belt which consists of the Dibsiyah and Sanama formations of the Wajid group. Similarities include sandstone composition, sedimentary environment, paleocurrent directions, unconformities, tectonic events, and influence of Gondwana glaciations. These formations and probably some or all the rest of the Paleozoic formations used to form one block but later separated after erosion caused by gradual tectonic growth, uplift, and prominence of the Arabian shield. During early Paleozoic time, the process started by poststabilization then sedimentation and at a later stage the growth and uplift of the shield occurred gradually. Growth of shields is a fact and it is the only way to explain the exposure of the Wajid sandstone on top of the highest mountain of the shield which exceeds 3,000 m in As Sawdah in Asir area in southwestern Saudi Arabia. The sandstone sediments of these outcrops were deposited on a low lying basin before been raised to this elevation.     

Analysis of lineaments within the Wajid Group,SW Saudi Arabia,and their tectonic significance

The Wajid Group is a Cambro-Permian sedimentary succession in southwest Saudi Arabia. This group is a well-known groundwater aquifer in the Wadi Al-Dawasir and Najran areas. The group also represents siliciclastic hydrocarbon reservoirs in the Rub' Al-Khali Basin. The Wajid Group is exposed in an area extending from Wadi Al-Dawasir southward to Najran city. This study aims to map and characterize the lineament traces of the Wajid Group outcrops. Landsat-8 OLI/TIRS satellite images with 30-m resolution, Spot-5 satellite images with 2.5-m resolution and SRTM digital elevation models (DEM) with 30-m resolution were used for lineament trace detection. Those lineament traces supplemented by aeromagnetic lineaments detected from reduced to pole magnetic anomaly map of the studied outcrop. Multi-scale lineament trace maps were generated, and the lineament datasets, including orientation and length, were analyzed statistically. Eight lineament trace trends were identified including NW-SE, NNW-SSE, N-S, NNE-SSW, NE-SW, ENE-WSW, E-W, and WNW-ESE. The northerly, northwesterly, and northeasterly trending lineament traces are predominant. The lineament trace lengths are generally followed the power law distribution. The lineament trace trends were validated through field investigation of the Wajid Group outcrop. The reported outcrop fracture trends are consistent with major lineament trace trends. Lineaments within the Wajid Group outcrop are also consistent with those of the southern portion of the Arabian Shield. The results of this study provide insight into the tectonic origin of the Wajid Group outcrop lineaments, and understanding of the lineaments distribution which can help to predict the fluid flow behavior within the groundwater fractured aquifers or hydrocarbon fractured reservoirs in Rub’ Al-Khali Basin.     

Drought and human adjustment in Saudi Arabia

Drought is one of the natural hazards which causes death and damage for property particularly in drylands of the world. Drought as a natural hazard tends to limit and disrupt human activities. On the other hand, man has tried to adjust his living conditions to this hazard. The adjustment to drought is different from one country to another. Adjustment to drought is affected by culture, income, and by the political system in the country. In the case of Saudi Arabia adjustment to drought hazard is usually the work of both individuals, and government. The Saudi Arabian government has spent large sums of money to reduce impact of drought hazard.     

Origin and geochemical reaction paths of sabkha brines: Sabkha Jayb Uwayyid, eastern Saudi Arabia

Sabkhas are ubiquitous geomorphic features in eastern Saudi Arabia. Seven brine samples were taken from Sabkha Jayb Uwayyid in eastern Saudi Arabia. Brine chemistry, saturation state with respect to carbonate and evaporate minerals, and evaporation-driven geochemical reaction paths were investigated to delineate the origin of brines and the evolution of both brine chemistry and sabkha mineralogy. The average total dissolved solids in the sabkha brines is 243 g/l. The order of cation dominance is Na⁺   >>  Mg²⁺ >>  Ca²⁺>K⁺, while anion dominance is Cl⁻ >> SO₄ ²⁻ >> HCO₃ ⁻. Based on the chemical divide principle and observed ion ratios, it was concluded that sabkha brines have evolved from deep groundwater rather than from direct rainfall, runoff from the surroundings, or inflow of shallow groundwater. Aqueous speciation simulations show that: (1) all seven brines are supersaturated with respect to calcite, dolomite, and magnesite and undersaturated with respect to halite; (2) three brines are undersaturated with respect to both gypsum and anhydrite, while three brines are supersaturated with respect to both minerals; (3) anhydrite is a more stable solid phase than gypsum in four brines. Evaporation factors required to bring the brines to the halite phase boundary ranged from 1.016 to 4.53. All reaction paths to the halite phase boundary follow the neutral path as CO₂ is degassed and dolomite precipitates from the brines. On average, a sabkha brine containing 1 kg of H₂O precipitates 7.6 g of minerals along the reaction path to the halite phase boundary, of which 52% is anhydrite, 35.3% is gypsum, and 12.7% is dolomite. Bicarbonate is the limiting factor of dolomite precipitation, and sulfate is the limiting factor of gypsum and anhydrite precipitation from sabkha brines.     

Provenance, diagenesis, tectonic setting and geochemistry of Tawil Sandstone (Lower Devonian) in Central Saudi Arabia

The Tawil Sandstone (Lower Devonian) in Central Saudi Arabia overlies the Sharwara Member of the Tayyarat Formation (Silurian) and succeeded conformly by the Shaiba Member of the Jauf Formation. Petrographical data reveal that the Tawil Sandstone comprises 96% quartz, 3% feldspar, and 1% rock fragments and all samples are classified as quartz arenites. The presence of well sorted, altered to fresh feldspar, and discriminate function analysis suggests that the sediments have been subjected to substartial reworking resulting in a high level of maturity. Modal analysis data (Q–F–L) suggest a stable cratonic provenance for the sediments and accumulation in a passive margin basin is indicated (binary plot of SiO₂ vs K₂O/Na₂O). Diagenetic features include dissolution of feldspar and rock fragments, compaction, reduction of the existing pore space through rearrangements, and rotation and fragmentation of grains resulting in dissolution of quartz grains and cementation.     

Health care pattern and planning in Saudi Arabia

Amazonia I is a large multi-disciplinary project, now in its fourth year, concerned with the effects of changing land use on the ecology and climate of the Brazilian Amazon. It is primarily concerned with investigating the water, carbon and nutrient cycles, and brings together about 80 scientists from a number of Brasilian institutes, but especially from INPA in Manaus, CENA/USP in Piracicaba and EMBRAPA/CPATU in Belem.Major activities include the better identification of water vapour producing precipitation, to establish better water vapour circulation models (via ¹⁸O, deuterium and ³H analysis, plus radiosonding); the study of water relations of isolated forest areas; the study of various phases of the carbon cycle especially soil organic matter; primary production; and nitrogen and soil fertility studies.A first phase Regional Amazon Model (RAM) for hydrology is being developed, and it should shortly be possible to make a first research-based attempt at modelling the carbon cycle of the Amazon region.This coordinated project represents in most ways the type of research required for the International Geosphere-Biosphere Programme (IGBP) and is a major Brasilian initiative.     

Geological and geotechnical aspects of Saudi Arabia

Summary This paper presents a brief review of the geological and geotechnical aspects of the Kingdom of Saudi Arabia. The first part of the paper presents a brief summary of the geological aspects and the soil characteristics in different parts of the country. The second part gives a brief outline of the major geotechnical problems encountered in the regions of the Kingdom along with their geographical locations.     

The scarp lands of Saudi Arabia

In central Saudi Arabia, the combination of rock types and sedimentary bedding created a unique scarp landscape. The escarpments were formed during Late Miocene through Early Quaternary times. At present, cuesta formation and migration are restricted to the actual escarpments as a consequence of negligible sediment removal. The plains between the escarpments are sealed through periodically active fluvial processes and through eolian sedimentation. In this publication, the major escarpments of central Saudi Arabia are described. The interactions between tectonics, climate, and morphogenesis which created this unique landscape are reviewed.