DESERTIFICATION ASSESSMENT USING THE ANALYTIC HIERARCHY PROCESS AND GIS IN SOUTHEAST IRAN   总被引：1，自引：0，他引：1       下载免费PDF全文

HOSSEIN NEGARESH  ZEINAB RAKHSHANI  FATEMEH FIROOZI  HADI ALINIA 《Geografiska Annaler: Series A, Physical Geography》2016,98(1):1-14

Studying the factors influencing desertification progress of a region and its resulting zoning can be effective in helping to reduce the damage of this phenomenon. This study attempted to investigate the factors influencing desertification progress; hence, it proceeded to zone Sistan and Baluchestan Province using three analytic hierarchy processes, Expert Choice software and a geographic information system. First, factors affecting desertification progress were checked and they were then used to determine the most important aspects in order of priority as follows: climatic elements (temperature, evaporation, wind, precipitation and humidity), morphology (topography and slope) and human factors (land cover). Then, a zoning map of desertification‐prone lands was prepared. The results showed that, in terms of hazard progress of these lands, there were five desertification hazard regions in Sistan and Baluchestan Province with an area of about 187 502 km² and high hazard regions covering approximately 29.2% of the province were located in the north of the province. High hazard regions with an approximate area of 3.20% of the total area of the province were mostly located in Saravan, Khash, and the surrounding areas; medium hazard regions with an approximate area of 19.6% were in Iranshahr and the southeastern part of the province; low hazard regions with an area of about 18.2% were in the southern parts of the province; and very low hazard regions with an approximate area of 12.7% were in Nikshahr and the southern parts of the province.  相似文献   

Early Cretaceous exhumation of high‐pressure metamorphic rocks of the Sistan Suture Zone,eastern Iran     

G. R. Fotoohi Rad  G. T. R. Droop  R. Burgess 《Geological Journal》2009,44(1):104-116

The Sistan Suture Zone (SSZ) of eastern Iran is part of the Neo‐Tethyan orogenic system and formed by convergence of the Central Iranian and Afghan microcontinents. Ar Ar ages of ca. 125 Ma have been obtained from white micas and amphibole from variably overprinted high‐pressure metabasites within the Ratuk Complex of the SSZ. The metabasites, which occur as fault‐bounded lenses within a subduction mélange, document peak‐metamorphic conditions in eclogite or blueschist facies followed by near‐isothermal decompression resulting in an epidote–amphibolite‐facies overprint. ⁴⁰Ar/³⁹Ar step heating experiments were performed on a phengite + paragonite mixture from an eclogite, phengites from two amphibolites, and paragonite from a blueschist; ‘best‐fit’ ages from these micas are, respectively, 122.8 ± 2.2, 124 ± 13, 116 ± 19 and 139 ± 19 Ma (2σ error). Barroisite from an amphibolite yielded an age of 124 ± 10 Ma. The ages are interpreted as cooling ages that record the post‐epidote–amphibolite stage in the exhumation of the rocks. Our results imply that both the high‐pressure metamorphism and the epidote–amphibolite‐facies overprint occurred prior to 125 Ma. Subduction of oceanic lithosphere along the eastern margin of the Sistan Ocean had therefore begun by Barremian (Early Cretaceous) times. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Depositional environments and ichnology of Upper Cretaceous deep-marine deposits in the Sistan Suture Zone,Birjand, Eastern Iran     

《Cretaceous Research》2016

The palaeoenvironmental significance of trace fossil assemblages in the flysch deposits of the Upper Cretaceous of the Sistan ocean – the Sefidabeh basin in the Sistan Suture Zone SSZ in Eastern Iran – has been assessed for the first time. The Sefidabeh basin of turbidite origin consists of 10 sedimentary facies, which can be grouped into 3 facies associations (FA) representing submarine channel-related facies associations (FA1), lobe-related facies associations (FA2), distal fan-basin floor facies associations of a deep-water turbidite system (FA3). Thirty three ichnogenera, with many ichnospecies, have been identified in this deep sea succession: Alcyonidiopsis, Arthrophycus, Asterostoma, Belorhaphe, Bergaueria, Cardioichnus, Chondrites, Cosmorhaphe, Desmograpton, Gyrophyllites, Halopoa, Helminthopsis, Helminthorhaphe, Laevicyclus, Lophoctenium, Mammilichnis, Megagrapton, Multina, Nereites, Ophiomorpha, Palaeophycus, Planolites, Phycodes, Phycosiphon, Paleodictyon, Rutichnus, Scolicia, ?Strobilorhaphe, Taenidium, Teichichnus, Thalassinoides, Zoophycos and Urohelminthoida. Their distribution is clearly linked with lithofacies and depositional palaeoenvironments. Changes in trace fossil assemblages and ichnocoenoses follow different environments of the turbidity system of the submarine channel to fan system of the Sefidabeh basin and are associated with variations in environmental controlling factors. Environmental controlling factors including hydrodynamic regime, oxygen level, organic content and sedimentation rates. Ten ichnocoenoses were recognized in the facies associations of the deep-sea fan system of this study. Taking into consideration the diversity, bioturbation level, and colonization order of bioturbated beds and the obvious deepening of the deep-sea depositional system from inner to outer parts of the succession, ichnocoenoses can express a bathymetric trend from shallower to deeper parts, and from higher-to-lower hydrodynamic condition of deep-sea fan systems of the Sefidabeh basin. This study reveals important sedimentological and ichnological features of turbiditic systems in deep sea settings of Iran and permits the development of predictive models for the palaeoenvironmental significance of trace fossil assemblages that can be readily translated to analogous depositional systems in the surface/subsurface.  相似文献   

Geochemistry of the Zargoli granite: Implications for development of the Sistan Suture Zone,southeastern Iran     

Mehdi Rezaei‐Kahkhaei  Ali Kananian  Dariush Esmaeily  Abbas Asiabanha 《Island Arc》2010,19(2):259-276

The Zargoli granite, which extends in a northeast–southwest direction, intrudes into the Eocene–Oligocene regional metamorphic flysch‐type sediments in the northwest of Zahedan. This pluton, based on modal and geochemical classification, is composed of biotite granite and biotite granodiorite, was contaminated by country rocks during its emplacement, and is slightly changed to more aluminous. The SiO₂ content of these rocks range from 62.4 to 66 wt% with an alumina saturation index of Shand [molar Al₂O₃/(CaO + Na₂O + K₂O)] ～ 1.1. Most of its chemical variations could be explained by fractionation or heterogeneous distribution of biotite. The features of the rocks resemble those which are typical to post‐collisional granitoids. Chondrite‐normalized rare‐earth element patterns of these rocks are fractionated at (La/Lu)_N = 2.25–11.82 with a pronounced negative Eu anomaly (Eu/Eu* = 3.25–5.26). Zircon saturation thermometry provides a good estimation of magma temperatures (767.4–789.3°C) for zircon crystallization. These characteristics together with the moderate Mg# [100Mg/(Mg + Fe)] values (44–55), Fe + Mg + Ti (millications) = 130–175, and Al–(Na + K + 2Ca) (millications) = 5–50 may suggest that these rocks have been derived from the dehydration partial melting of quartz–feldspathic meta‐igneous lower crust.  相似文献