A spectral index for land degradation mapping using ASTER data: Application to a semi-arid Mediterranean catchment     

《International Journal of Applied Earth Observation and Geoinformation》2005,7(2):140-153

Flagrant soil erosion in Morocco is an alarming sign of soil degradation. Due to the considerable costs of detailed ground surveys of this phenomenon, remote sensing is an appropriate alternative for analyzing and evaluating the risks of the expansion of soil degradation. In this paper, we characterize the state of land degradation in a small Mediterranean watershed using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data and ground-based spectroradiometric measurements. The two visible, the near-infrared and six shortwave infrared bands of the above sensor were calibrated using ground measurements of the spectral reflectance. Field measurements were carried out in the Saboun experimental basin located in the marl soil region of the Moroccan western Rif. The study leads to the development and evaluation of a new spectral approach to express land degradation. This index called Land degradation index (LDI) is based on the concept of the soil line derived from spectroradiometric ground measurements. In this study, we compare LDI and the spectral angle mapping (SAM) approaches to assess and map land degradation. Results show that LDI provides more accurate results for mapping land degradation (Kappa = 0.79) when compared to the SAM method (Kappa = 0.61). Validation and evaluation of the results are based on the thematic maps derived from the ground data (organic matter, clay, silt and sand) by kriging, DEM, slope gradient and photointerpretation.  相似文献   

Interpretation of Holocene lake-level change from diatom assemblages in Lake Sidi Ali,Middle Atlas,Morocco   总被引：1，自引：0，他引：1  

P. A. Barker  N. Roberts  H. F. Lamb  S. van der Kaars  A. Benkaddour 《Journal of Paleolimnology》1994,12(3):223-234

While palaeohydrological changes in non-outlet lakes provide a key proxy indicator of past climatic fluctuations, for lake systems which have been chemically insensitive, it is necessary to use indicators of water depth rather than salinity to reconstruct their hydro- climatic histories. A study of diatoms in the modern sediments of Sidi Ali, a non-outlet lake in the Middle Atlas of Morocco, has shown a statistically significant correlation between water depth and the ratio of planktonic to littoral diatoms. This relationship is used to calibrate fossil diatom assemblages from a lake sediment core from the same lake to provide a quantitative index of water levels over the pastc. 6500 years. Palaeoecological evidence suggests that climatically induced hydrological variations have dominated the bulk of the mid-late Holocene lake sediment record, with significant human-induced catchment disturbance only occurring during the twentieth century. The pattern of water depth fluctuations suggests that the response time of the regional groundwater system to climatic forcing is <100 years.This is the third in a series of papers published in this issue on the paleolimnology of arid regions. These papers were presented at the Sixth International Palaeolimnology Symposium held 19–21 April, 1993 at the Australian National University, Canberra, Australia. Dr A. R. Chivas served as guest editor for these papers.  相似文献   

Groundwater pollution risk mapping for the Eocene aquifer of the Oum Er-Rabia basin, Morocco   总被引：2，自引：0，他引：2  

Said Ettazarini 《Environmental Geology》2006,51(3):341-347

Sustainable development requires the management and preservation of water resources indispensable for all human activities. When groundwater constitutes the main water resource, vulnerability maps therefore are an important tool for identifying zones of high pollution risk and taking preventive measures in potential pollution sites. The vulnerability assessment for the Eocene aquifer in the Moroccan basin of Oum Er-Rabia is based on the DRASTIC method that uses seven parameters summarizing climatic, geological, and hydrogeological conditions controlling the seepage of pollutant substances to groundwater. Vulnerability maps were produced by using GIS techniques and applying the “generic” and “agricultural” models according to the DRASTIC charter. Resulting maps revealed that the aquifer is highly vulnerable in the western part of the basin and areas being under high contamination risk are more extensive when the “agricultural” model was applied.  相似文献   

Distinguishing eustatic and epeirogenic controls on Lower–Middle Cambrian boundary successions in West Gondwana (Morocco and Iberia)     

ED LANDING  GERD GEYER†  WOLFRAM HELDMAIER† 《Sedimentology》2006,53(4):899-918

Major eustatic fall has been invoked to explain Lower–Middle Cambrian boundary sandstones and faunal replacements on a number of Cambrian palaeocontinents. This proposal has been tested on the Moroccan and Spanish margins of West Gondwana and found to be inadequate to explain stratigraphical developments. In these regions, sandstone intervals long presumed to be regressive and late Early Cambrian in age are now shown to be early Middle Cambrian, and composed of a lower regressive and an overlying transgressive sandstone separated by a regional unconformity. Only the lower tidalites (i.e. Tazlaft Formation in Morocco and lower Daroca sandstones in Spain) record the Hawke Bay eustatic regression in West Gondwana. The Tazlaft is overlain by a newly recognized, unconformably overlying sandstone (Talelt Formation) that onlapped southern Morocco with reactivation of a pull‐apart or transcurrent regime. Up to 150 m of erosion on uplifted blocks in the High Atlas range and foundering of the Souss Basin to the south preceded onlap and deposition of the volcanic‐rich Tatelt, the correlative and depositional analogue of the upper Daroca and lower Valdemides Formations in northern Spain. With folding and erosion, a type 1 depositional sequence boundary also caps the Tatelt at its contact with an overlying, lower Middle Cambrian mudstone‐dominated succession. This unconformity probably occurs in Spain within the Valdemiedes Formation and corresponds to a faunal discontinuity called the ‘Valdemiedes geoevent’. The Iberian ‘Daroca regression’ and Moroccan ‘Asrir regression’ are misnomers, as the sandstones on which they are based are composite units with a lower regressive interval that records eustatic fall and an upper transgressive unit that records epeirogenically driven onlap.  相似文献   

Modélisation magnétique de la suture ophiolitique de Bou Azzer–El Graara (Anti-Atlas central,Maroc). Implications sur la reconstitution géodynamique panafricaine     

Abderrahmane Soulaimani  Mohammed Jaffal  Lhou Maacha  Azzouz Kchikach  Abdessamad Najine  Abdellatif Saidi 《Comptes Rendus Geoscience》2006,338(3):153-160

Aeromagnetic data of the Anti-Atlas Mountains show an important magnetic anomaly along the ‘Major Anti-Atlas Fault’, produced by different mafic and ultramafic rocks of a Neoproterozoic ophiolite complex. The magnetic modelling of Bou Azzer–El Graara ophiolitic suture shows a deep-seated anomaly through the upper continental crust corresponding to a north-dipping subduction. The polarity of the Pan-African subduction in the Anti-Atlas is therefore compatible with the contemporaneous Pan-African orogenic belts, where polarity of subduction dipped away from the West African Craton during the amalgamation of Western Gondwana. To cite this article: A. Soulaimani et al., C. R. Geoscience 338 (2006).  相似文献   

Neoliberalism, environmentalism, and agricultural restructuring in Morocco     

DIANA K DAVIS 《The Geographical journal》2006,172(2):88-105

Neoliberal restructuring in Morocco has been taking place for over twenty years. Beginning with a decade of structural adjustment, from the early 1980s to the early 1990s, parts of the public sector have been privatized, state services such as health care and education reduced, tariffs lowered and exports heavily promoted. In the dryland agricultural areas, a declensionist colonial environmental narrative has been appropriated to help justify and implement the neoliberal goals of land privatization and the intensification of agricultural production in the name of environmental protection. This paper contributes to areas of growing interest for geographers through an analysis of the underexplored relationship between neoliberalism and environmentalism, in the form of questionable environmental narratives, in Morocco. Land degradation in the dryland agricultural areas of Morocco is commonly blamed on overgrazing by local pastoralists despite existing documentation that suggests instead that ploughing of marginal lands and over-irrigation are the primary drivers of land degradation in the region. The deployment of this colonial environmental narrative of 'native improvidence' has facilitated an expansion of state power over collective rangelands under neoliberalism at the same time that government involvement has decreased in other sectors. The effects of neoliberalism in Morocco have been complex and thus the paper argues that current neoliberal reforms such as the Morocco–US free trade agreement need to be scrutinized carefully to prevent a further exacerbation of poverty as well as to prevent further land degradation in these areas.  相似文献   

New plesiosaurian specimens (Reptilia,Plesiosauria) from the Upper Cretaceous (Turonian) of Goulmima (Southern Morocco)     

《Cretaceous Research》2018

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Structural evolution of the southern Rif Cordillera (Morocco): tectonics and synsedimentary fault processes     

Lahcen Zouhri 《Geological Journal》2004,39(1):81-93

This paper attempts to investigate the tectonics of the southern Rif Cordillera. Hydrogeological and oil well data, together with interpretation of seismic reflection lines help to characterize the architecture of the Rharb–Mamora Basin located in the frontal region of the Gibraltar Arc. The facies map constructed from the drilling data exhibits four main types of Pliocene facies: (i) conglomerates; (ii) limestones; (iii) sandstones and sands more or less rich with shelly remains; (iv) clays. The lateral variation of deposits is accompanied by thickening, which can reach a few tens of metres. Thickening of layers and lithofacies variation indicate synsedimentary faulting processes. Two major fault zones have been identified: Kenitra–Sidi Slimane Fault Zone (K2SFZ) and Rabat–Kenitra Fault Zone (RKFZ). In the western coastal area, the geometrical configuration suggests a partition into horsts and grabens in the southern part, and a system of three geological units in the northern part. The analysis and interpretation of the gravity data reveal an important gravity anomaly, referred to as the Kenitra Gravity Anomaly. It corresponds to the Hercynian faults deduced by the seismic reflection line interpretation: K2SFZ and RKFZ. From Larache to El Jadida cities, the Kenitra area represents the hinge between the positive and negative gravity values, with a major negative anomaly in the eastern part of Kenitra. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Chronology of Upper Pleistocene sequences at Sidi Messaoud (wadi Noun, southwestern Morocco) based on C, optical and U-series dating     

Norbert Mercier  Christine Hatt  Michel Fontugne  Jean-Louis Reyss  Hlne Valladas  Luc Wengler  Jean-Philip Brugal  Abderrahmane Ouammou  Andr Weisrock 《Quaternary Geochronology》2009,4(4):326-334

The Sidi Messaoud site provides a 40 m thick sedimentary infilling of great importance for the study of environmental changes and landscape evolution during the Upper Pleistocene in the Western Sahara. In this study, chronological results obtained by the ¹⁴C, U-series and optical dating techniques are compared. Each individual age, depositional environment and post-deposition history of the various samples are evaluated, in order to explain the methodological reasons for discordances and concordances. Stratigraphic and palaeoenvironmental implications for the last 120 ka history in southwestern Morocco are also inferred: the wadi Noun gorges had been incised before MIS 5, and later, during MIS 3, the valley has been filled in with a mean sedimentation rate of 1 m/ka.  相似文献   

利用反投影技术快速测定中强震矩震级及破裂过程——以2023年9月9日摩洛哥MW6.9地震为例     

韩光洁  孙丽  杨志高 《中国地震》2023,39(3):680-688

利用远场台阵反投影技术可以较少地依赖先验经验,于震后快速获得震源破裂过程时空分布特征,并据此估算矩震级。本文使用美国阿拉斯加宽频带台阵记录到的远场直达P波数据,基于反投影方法,对2023年9月9日摩洛哥M_W6.9地震震源破裂过程及震级进行分析。结果显示,地震破裂走向以NE-SW向为主,地震能量在10～20s集中在震中距10km范围内释放,与震源机制解和震中区亚特拉斯山脉走向基本一致。震源破裂持续时间结合在全球分布均匀的GSN台网记录到的P波最大位移数据,在震后约15min即可快速估算出本次地震矩震级为M_W7.0,与中国地震台网中心和美国地质调查局发布震级基本一致。  相似文献