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91.
The present study has been undertaken to determine the nature and the factors controlling the distribution of carbonate content in Kuwait Bay sediments. The carbonate content that may be deposited with Kuwait Bay sediments is attributed to the interplay of the deposits fallout from the dust storms over Kuwaiti territory, the deposits carried in suspension by the currents from Shatt Al-Arab area and to the skeletal parts of microorganisms that may be originated in the sediments. The carbonate content increases in the coarse sediments rather than in the fine sediments. The mineral components of the carbonate present are in the form of calcite, aragonite and some dolomite. Therefore, the texture of the sediments, the rate of deposition in addition to the biological interference may exert a considerable control over carbonate distribution. 相似文献
92.
A possible suture between an old craton in West Africa and the Arabian—Nubian shield is marked by a persistent zone of Phanerozoic weakness. This zone extends between the Nile and Niger deltas and passes through the Qattara embayment, along the Bahariya fault, through the Kufra basin, between the Tibesti and Jabal al Uwaynat massifs, through the Bahr el Ghazal and Lake Chad areas, and along the Benoue trough. 相似文献
93.
Thomas Binet Pierre Failler Pablo N. Chavance Mohamed Abidine Mayif 《Global Environmental Change》2013,23(6):1434-1443
This article investigates whether the European Union-Mauritania fisheries agreement, which allocates part of the Europe's financial contribution to the conservation of marine ecosystems located within the Banc d’Arguin National Park, can be regarded as a payment for ecosystem service. A framework for qualification as such payment scheme was established based on an extensive literature review. The criteria identified for the qualification as a payment to ecosystem service pertain to: (1) the definition of the ecosystem service(s) involved; (2) the mechanism involved by the payment; and (3) the nature of the transaction. Interviews with local beneficiaries and subsequent data analysis led to the conclusion that this mechanism could be regarded as a payment to ecosystem service and so, through the European Union-Mauritania Fisheries agreement, the European Union were investing to protect local fish resources that could be exploited by its fishing fleet. This agreement, involving the first International Payment to Ecosystem Service of this kind, marks an important step towards better consideration of marine conservation in international public policy and foreign fishing policy in particular. However, this payment is small when compared to revenues generated through the exploitation of developing countries’ fishing grounds by fishing countries. Nevertheless it opens the door for more detailed applications of payment to ecosystem service schemes to other ecosystems contexts, and can provide a useful alternative source of financing of marine biodiversity conservation. 相似文献
94.
GIS and multi-criteria analysis to select potential sites of agro-industrial complex 总被引:1,自引:1,他引:0
Houda Sahnoun Mohamed Moncef Serbaji Boubaker Karray Khaled Medhioub 《Environmental Earth Sciences》2012,66(8):2477-2489
The selection of the potential sites to the creation of an agro-industrial complex requires a large amount of spatial information. Geographical information systems are capable of managing this information, providing the ability to integrate multiple layers of information and deriving new ones. This study incorporates environmental, social, economic, geological and infrastructural data. A multi-criteria analysis is performed to select the potential sites to the creation of an agro-industrial complex in the city of Sfax (the southern coast of Tunisia). The comparison by pair method adopted in this paper, based on a linear combination pondered after having assigned to every factor of decision a coefficient of level-headedness, creates many scenarios among which we selected the sustainable development one. This scenario assigned the highest weight to the economical, environmental and social factors (0.3 for each factor), which shows the presence of nine suitable sectors for the creation of an agro-industrial complex. The ELECTRE method enabled us to make a site ordering for the identification of the most three appropriate sites. 相似文献
95.
Philippe Vernant Abdelali Fadil Taoufik Mourabit Driss Ouazar Achraf Koulali Jose Martin Davila Jorge Garate Simon McClusky Robert Reilinger 《Journal of Geodynamics》2010,49(3-4):123-129
We present GPS observations in Morocco and adjacent areas of Spain from 15 continuous (CGPS) and 31 survey-mode (SGPS) sites extending from the stable part of the Nubian plate to central Spain. We determine a robust velocity field for the W Mediterranean that we use to constrain models for the Iberia-Nubia plate boundary. South of the High Atlas Mountain system, GPS motions are consistent with Nubia plate motions from prior geodetic studies. We constrain shortening in the Atlas system to <1.5 mm/yr, 95% confidence level. North of the Atlas Mountains, the GPS velocities indicate Nubia motion with respect to Eurasia, but also a component of motion normal to the direction of Nubia-Eurasia motion, consisting of southward translation of the Rif Mountains in N Morocco at rates exceeding 5 mm/yr. This southward motion appears to be directly related to Miocene opening of the Alboran Sea. The Betic Mountain system north of the Alboran Sea is characterized by WNW motion with respect to Eurasia at ~1–2 mm/yr, paralleling Nubia-Eurasia relative motion. In addition, sites located in the Betics north of the southerly moving Rif Mountains also indicate a component of southerly motion with respect to Eurasia. We interpret this as indicating that deformation associated with Nubia-Eurasia plate motion extends into the southern Betics, but also that the Betic system may be affected by the same processes that are causing southward motion of the Rif Mountains south of the Alboran Sea. Kinematic modeling indicates that plate boundary geometries that include a boundary through the Straits of Gibraltar are most compatible with the component of motion in the direction of relative plate motion, but that two additional blocks (Alboran-Rif block, Betic Mountain block), independent of both Nubia and Eurasia are needed to account for the motions of the Rif and Betic Mountains normal to the direction of relative plate motion. We speculate that the southward motions of the Alboran-Rif and Betic blocks may be related to mantle flow, possibly induced by southward rollback of the subducted Nubian plate beneath the Alboran Sea and Rif Mountains. 相似文献
96.
Martin Menzies Dan Bosence Hamed A. El-Nakha Salah Al-Khirbash Mohamed A. Al-Kadasi Abdulkarim Al Subbary 《地学学报》1990,2(4):340-350
This paper analyses new field and radiometric age data on the timing of extension, sedimentation and magmatism related to the opening of the Red Sea. The first evidence of widespread extension is found in synsedimentary fissures in the fluviatile to shallow marine Tawilah Formation of Cretaceous to early Tertiary age. The first indication of magmatism is the eruption of alkaline basalts (43.5–21.2 Ma) on to marine and non-marine sandstones of lower to middle Tertiary age. The lack of an angular unconformity at the sediment-basalt contact, over a period of 25 Myr, corroborates a diachronous relationship between the Tawilah sandstones and the Yemen Volcanics. These data also indicate that the onset of volcanism in Yemen was in the Eocene, as is the case in Ethiopia and Saudi Arabia. A passive rifting model is supported by early extension and sedimentation followed by syn- and post-tectonic magmatism. 相似文献
97.
Alaa I. Ibrahim Hisham Anwer Mohamed H. Soliman Nicholas Mackie-Jones Kalvir S. Dhuga William C. Parke Jean H. Swank Tilan Ukwatta M. T. Hussein T. El-Sherbini 《Astrophysics and Space Science》2007,308(1-4):535-539
A 6.4 keV emission line was discovered in an unusual burst from the soft gamma repeater SGR 1900+14 with the Rossi X-ray Timing
Explorer (RXTE). The line was detected in part of a complex multipeak precursor that preceded the unusual burst of 1998 August
29, i.e. two days after the giant flare of August 27 from the source. The origin of the line was not firmly identified and
two possible interpretations were equally plausible including (a) Kα fluorescence from a small iron rich material that was ejected to the magnetosphere during the August 27 flare, and (b) proton
or α-particle cyclotron resonance. If the iron scenario was correct, we expect to find evidence for the line during the intervening
interval between the flare and the August 29 burst, i.e. on August 28. Here we present the results of the August 28 burst
observation, taken with RXTE. We detect a total of seven bursts whose individual and joint spectra do not show evidence for
spectral lines. We also investigated a sample of nine bursts before and after the August 29 burst (from 1998 June to December)
that do not reveal evidence for a spectral line near 6.4 keV or elsewhere. These results disfavor the iron scenario and make
the proton/α-particle cyclotron resonance interpretation more plausible. The appearance of the emission line in part of a complex burst
and its absence from the studied sample indicate that the line is likely due to a transient phenomenon that may depend on
the burst morphology, energetics and the properties of the emission region.
相似文献
98.
Gamal M. El-Shabrawy Elena V. Anufriieva Mousa O. Germoush Mohamed E. Goher Nickolai V. Shadrin 《中国海洋湖沼学报》2015,33(6):1368-1377
Zooplankton and 14 abiotic variables were studied during August 2011 at 10 stations in Lake Qarun,Egypt.Stations with the lowest salinity and highest nutrient concentrations and turbidity were close to the discharge of waters from the El-Bats and El-Wadi drainage systems.A total of 15 holozooplankton species were identified.The salinity in Lake Qarun increased and fluctuated since 1901:12 g/L in 1901;8.5 g/L in 1905;12.0 g/L in 1922;30.0 g/L in 1985;38.7 g/L in 1994;35.3 g/L in 2006,and 33.4 g/L in 2011.The mean concentration of nutrients(nitrate,nitrite and orthophosphate) gradually increased from 35,0.16 and 0.38 ? g/L,respectively,in 1953–1955 to 113,16.4,and 30.26 ? g/L in 2011.From 1999–2003 some decrease of species diversity occurred.Average total zooplankton density was 30 000 ind./m 3 in 1974–1977;356 125 ind./m 3 in 1989;534 000 ind./m 3 in 1994–1995;from 965 000 to 1 452 000 ind./m 3 in 2006,and 595 000 ind./m 3 in 2011.A range of long-term summer salinity variability during the last decades was very similar to a range of salinity spatial variability in summer 2011.There is no significant correlation between zooplankton abundance and salinity in spatial and long-term changes.We conclude that salinity fluctuations since at least 1955 did not directly drive the changes of composition and abundance of zooplankton in the lake.A marine community had formed in the lake,and it continues to change.One of the main drivers of this change is a regular introduction and a pressure of alien species on the existent community.Eutrophication also plays an important role.The introduction of Mnemiopsis leidyi,first reported in 2014,may lead to a start of a new stage of the biotic changes in Lake Qarun,when eutrophication and the population dynamics of this ctenophore will be main drivers of the ecosystem change. 相似文献
99.
Daniela Comelli Massimo D'orazio Luigi Folco Mahmud El‐Halwagy Tommaso Frizzi Roberto Alberti Valentina Capogrosso Abdelrazek Elnaggar Hala Hassan Austin Nevin Franco Porcelli Mohamed G. Rashed Gianluca Valentini 《Meteoritics & planetary science》2016,51(7):1301-1309
Scholars have long discussed the introduction and spread of iron metallurgy in different civilizations. The sporadic use of iron has been reported in the Eastern Mediterranean area from the late Neolithic period to the Bronze Age. Despite the rare existence of smelted iron, it is generally assumed that early iron objects were produced from meteoritic iron. Nevertheless, the methods of working the metal, its use, and diffusion are contentious issues compromised by lack of detailed analysis. Since its discovery in 1925, the meteoritic origin of the iron dagger blade from the sarcophagus of the ancient Egyptian King Tutankhamun (14th C. BCE) has been the subject of debate and previous analyses yielded controversial results. We show that the composition of the blade (Fe plus 10.8 wt% Ni and 0.58 wt% Co), accurately determined through portable x‐ray fluorescence spectrometry, strongly supports its meteoritic origin. In agreement with recent results of metallographic analysis of ancient iron artifacts from Gerzeh, our study confirms that ancient Egyptians attributed great value to meteoritic iron for the production of precious objects. Moreover, the high manufacturing quality of Tutankhamun's dagger blade, in comparison with other simple‐shaped meteoritic iron artifacts, suggests a significant mastery of ironworking in Tutankhamun's time. 相似文献
100.
This is an overview of the mode of formation of the Nile Gorge in northern Egypt. It is based on the interpretation of the Shuttle Radar Topography Mission (SRTM) data along with detailed analysis of landsat image, geological map and seismic data. The results show that the current course of the Nile was caused by a differential uplift of two plateaus: Ma'aza, to the east, and Western Desert plateau, to the west of the river. This uplift is caused by dynamic forces resulting from subsurface convection processes. It also contributed to the formation of several drainage systems, basins and structural features. Abundant faults and fractures that are parallel to the Nile Valley on both flanks that are associated with uplift are proven to be contemporaneous with formation of the river. We conclude that understanding of the uplift is crucial to visualizing the Nile course and its geodynamic formation. The information derived from the SRTM data reveals invaluable knowledge in support of the presented remotely sensed geological features. The paper clearly explains the stages of formation of the Nile segments in space and time and structural controls on the path of the Nile River in Egypt. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献