Tectonic implications of felsic tuffs within the Lower Miocene Gangrinboche conglomerates,southern Tibet     

Jonathan C. Aitchison  Jason R. Ali  Angel Chan  Aileen M. Davis  Ching-Hua Lo 《Journal of Asian Earth Sciences》2009,34(3):287-297

Felsic tuffs are interbedded with the Gangrinboche conglomerates adjacent to the Yarlung Tsangpo suture zone in southern Tibet. Laser Ar/Ar dating of mineral separates indicates they are of Early Miocene age. Such tuffs are most likely an eruptive manifestation of geochemically indistinguishable coeval felsic (adakitic) intrusions that are widely reported across southern Tibet. The considerable lateral (E–W) extent of the Gangrinboche conglomerates and their depositional setting indicates sediment accumulation in an overall N–S compressional regime and thereby places important constraints on the tectonic setting in which magmatism initiated. The conglomerates were folded and truncated during back-thrusting associated with development of the north-directed Great Counter thrust. As N–S trending rifts associated with E–W extension of the Tibetan Plateau cut both the conglomerates and this thrust system it can be inferred that post-collisional volcanism is unlikely to have been genetically linked to later E–W extension. Early Miocene slab break-off beneath Tibet provides a model that appears to be consistent with petrogenesis of the associated magmatic suite, which requires a lowermost crust or lithospheric mantle generation, molasse accumulation, and uplift and emplacement of North Himalayan gneiss domes.  相似文献   

Flooding and its relationship with land cover change,population growth,and road density     

Mahfuzur Rahman  Chen Ningsheng  Golam Iftekhar Mahmud  Md Monirul Islam  Hamid Reza Pourghasemi  Hilal Ahmad  Jules Maurice Habumugisha  Rana Muhammad Ali Washakh  Mehtab Alam  Enlong Liu  Zheng Han  Huayong Ni  Tian Shufeng  Ashraf Dewan 《地学前缘(英文版)》2021,12(6):16-35

Bangladesh experiences frequent hydro-climatic disasters such as flooding.These disasters are believed to be associated with land use changes and climate variability.However,identifying the factors that lead to flooding is challenging.This study mapped flood susceptibility in the northeast region of Bangladesh using Bayesian regularization back propagation(BRBP)neural network,classification and regression trees(CART),a statistical model(STM)using the evidence belief function(EBF),and their ensemble models(EMs)for three time periods(2000,2014,and 2017).The accuracy of machine learning algorithms(MLAs),STM,and EMs were assessed by considering the area under the curve-receiver operating char-acteristic(AUC-ROC).Evaluation of the accuracy levels of the aforementioned algorithms revealed that EM4(BRBP-CART-EBF)outperformed(AUC＞90％)standalone and other ensemble models for the three time periods analyzed.Furthermore,this study investigated the relationships among land cover change(LCC),population growth(PG),road density(RD),and relative change of flooding(RCF)areas for the per-iod between 2000 and 2017.The results showed that areas with very high susceptibility to flooding increased by 19.72％between 2000 and 2017,while the PG rate increased by 51.68％over the same period.The Pearson correlation coefficient for RCF and RD was calculated to be 0.496.These findings highlight the significant association between floods and causative factors.The study findings could be valuable to policymakers and resource managers as they can lead to improvements in flood management and reduction in flood damage and risks.  相似文献   

乌鲁木齐市城区和郊区近地层风速廓线     

金莉莉  李振杰  何清  缪启龙  买买提艾力&#  买买提依明 《中国沙漠》2017,37(4):755-769

利用乌鲁木齐市5座100 m气象塔10层风速观测资料,分析了乌鲁木齐市城区和郊区近地层风速季节变化和日变化特征。结果表明：（1）乌鲁木齐市风速最大值出现在14：00-16：00,最小值多在夜间或上午。冬季风速最小、夏季最大;冬季风速始终处于较为稳定、有微小波动的低值区;夏季风速表现出一定的变化趋势。（2）夏季风速在一年里波动最大,随地势降低波动减小,南郊最大（1.5~6.4 m·s^-1）,北郊最小（1.3~4.6 m·s^-1）;秋季和春季风速波动次之;冬季风速波动最小,南郊最大（1.3~4.6 m·s^-1）,北郊最小（0.7~2 m·s^-1）。（3）近地层100 m内城区和北郊风速随高度变化较小,冬季基本为1~2 m·s^-1,而南郊风速随高度增加变化幅度最大,从1 m·s^-1增加到4 m·s^-1以上;愈近地面,城区与郊区风速相差愈大,近地面城区平均风速明显低于郊区,春季、夏季、秋季和冬季分别低5%~32%、8%~30%、15%~37%、14%~48%。（4）近地层风速廓线在近中性层结时一般符合对数风速廓线模式,对数律显著性不强的时段主要在正午前后。  相似文献   

Geochronology,geochemistry, and tectonic setting of the Oligocene magmatic rocks (Marmaros Magmatic Assemblage) in Gökçeada Island,northwest Turkey     

Ali Elmas  Ersin Koralay  Olgun Duru  Alexander Schmidt 《International Geology Review》2017,59(4):420-447

Through the ?zmir–Ankara–Erzincan and the Vardar oceans suture zones, convergence between the Eurasian and African plates played a key role in controlling Palaeogene magmatism in northwestern Anatolia, northern Aegean, and eastern Balkans. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the tuffs of the Harmankaya Volcanic Rocks, which are inter-fingered with the lower-middle Eocene deposits of the Gaziköy Formation to the north of the Ganos Fault and the Karaa?aç Formation in the Gelibolu Peninsula, yielded a late Ypresian (51 Ma) age. The chemical characteristics suggest that the lavas and tuffs of the Harmankaya Volcanic Rocks are products of syn- or post-collision magmas. These volcanic rocks show also close affinities to the subduction-related magmas. In addition to the already known andesitic volcanic rocks, our field observations in Gökçeada Island indicate also the existence of granitic and rhyolitic rocks (Marmaros Magmatic Assemblage). Our U–Pb zircon age data has shown that the newly discovered Marmaros granitic plutons intruded during late Oligocene (26 Ma) into the deposits of the Karaa?aç Formation in Gökçeada Island. LA-ICP-MS dating of U and Pb isotopes on zircon separates from the Marmaros rhyolitic rocks yielded a late Oligocene (26 Ma) crystallization age. Geochemical characteristics indicate that the more-evolved Oligocene granitic and rhyolitic rock of the Marmaros Magmatic Assemblage possibly assimilated a greater amount of crustal material than the lower Eocene Harmankaya Volcanic Rocks. Geochemical features and age relationships suggest increasing amounts of crustal contamination and a decreasing subduction signature during the evolution of magmas in NW Turkey from the early Eocene to the Oligocene. The magmatic activity developed following the northward subduction of the ?zmir–Ankara–Erzincan oceanic lithosphere and the earliest Palaeocene final continental collision between the Sakarya and Anatolide–Tauride zones.  相似文献   

High-throughput production of peroxidase and its biodegradation potential toward polymeric material     

N. Khatoon  N. I. Sahar  U. Ndu  N. Ali  A. Jamal  S. Ahmed  M. I. Ali 《International Journal of Environmental Science and Technology》2017,14(4):755-766

Plastics are polymeric materials, and their disposal is a great problem in today’s society. Large quantities of single-use plastics are used every minute throughout the world. Peroxidase enzymes play a significant role in the biodegradation of polymeric materials due to oxidoreductase capability. The objective is to determine which set of conditions optimize the production of peroxidase enzymes by Phanerochaete chrysosporium so as to degrade polymeric materials. The sequential order of parameters in terms of their relevant performance in the bioprocess was determined as urea > polyvinyl chloride > incubation time > polyethylene > veratryl alcohol > sucrose > ammonium sulfate > glucose > ferrous sulfate and polystyrene. Statistical analysis was performed by using analysis of variance which indicated the significance of model Plackett–Burman and components on the basis of F value and P value of 0.012678 < 0.05. The Fourier transform infrared spectroscopy of enzyme-treated polymer revealed structural changes at 1091, 1638 cm^?1. A new peak appeared at wave number 1029 and represented the aromatic ether and phenolic group as compared to control. Biosynthesis of lignin peroxidase at optimized conditions has the potential for biodegradation of recalcitrant polymeric waste, due to its oxidoreductase capability for chemically inert material in nature like lignin and can be used for waste treatment on a large scale.  相似文献   

Integration of inland and coastal storms for flood hazard assessment using a distributed hydrologic model     

Mohammad Karamouz  Ali Razmi  Sara Nazif  Zahra Zahmatkesh 《Environmental Earth Sciences》2017,76(11):395

Due to increasing flood severities and frequencies, studies on coastal vulnerability assessment are of increasing concern. Evaluation of flood inundation depth and extent is the first issue in flood vulnerability analysis. This study has proposed a practical framework for reliable coastal floodplain delineation considering both inland and coastal flooding. New York City (NYC) has been considered as the case study because of its vulnerability to storm surge-induced hazards. For floodplain delineation, a distributed hydrologic model is used. In the proposed method, the severities of combined inland and coastal floods for different recurrence intervals are determined. Through analyzing past storms in the study region, a referenced (base) configuration of rainfall and storm surge is selected to be used for defining flood scenarios with different return periods. The inundated areas are determined under different flooding scenarios. The inundation maps of 2012 superstorm Sandy in NYC is simulated and compared with the FEMA revised maps which shows a close agreement. This methodology could be of significant value to the planners and engineers working on the preparedness of coastal urban communities against storms by providing a platform for updating inundation maps as new events are observed and new information becomes available.  相似文献   

Hydrogeochemical characteristics prediction using multiple linear regression: case study on unconfined aquifer in northeastern Tunisia     

Zouheira Ibn Ali  Youssef Frika  Lamia Laajili Ghzel  Moncef Zairi 《Arabian Journal of Geosciences》2017,10(17):382

The main factors and mechanisms controlling the groundwater chemistry and mineralization are recognized through hydrochemical data. However, water quality prediction remains a key parameter for groundwater resources management and planning. The geochemical study of groundwater of a multilayered aquifer system in Tunisia is recognized by measurements of the pH, EC, total dissolved solids (TDS), major ion concentration and nitrates of 36 samples from pumping wells covering the aquifer extension and analyzed using standard laboratory and field methods. The calcite precipitation, gypsum, anhydrite and halite dissolution, and direct and reverse ion exchange are the principal process of chemical evolution in the Nadhour-Saouaf aquifer system. Using stepwise regression, the concentration groups of (Ca, Cl, and NO₃), (Cl, SO₄, and Mg), and (Ca and Na) exhibit significant prediction of TDS in Plio-Quaternary, Miocene, and Oligocene aquifer levels, respectively. The highest values of R ² and adjusted R ² close to 1 revealed the accuracy of the developed models which is confirmed by the weak difference between the measured and estimated values varying between ?12 and 8%. The important uncertainty parameters that affected the estimated TDS are assessed by the sensitivity analysis method. The concentration of (Cl), (Ca and Cl), and (Na) are the major parameters affecting the TDS sensitivity of the Plio-Quaternary, Miocene, and Oligocene aquifer levels, respectively. Hence, the developed TDS models provide a more simple and easy alternative to other methods used for groundwater quality estimation and prediction as proven from external validation on groundwater samples unconsidered in the model construction.  相似文献   

Effect of watershed partitioning on hydrologic parameters and estimation of hydrograph of an ungauged basin: a case study in Gokirmak and Kocanaz,Turkey     

Müsteyde Baduna Koçyiğit  Hüseyin Akay  Ali Melih Yanmaz 《Arabian Journal of Geosciences》2017,10(15):331

The main goal of this study is to investigate the effect of the size of the subbasins of a watershed on the hydrologic parameters and their spatial variability in an estimation of the hydrologic parameters and hydrograph of a neighbouring ungauged basin. In this paper, Hydrologic Engineering Center-Hydrologic Modelling System (HEC-HMS), a semi-distributed hydrologic model, is used to calibrate and cross-validate two flood events occurred in 1998 and then validate four other flood events occurred in 1991, 1994, 2002, and 2009 in Gokirmak Basin in Western Black Sea Region, Turkey. The basin is divided into seven different subbasins to investigate the effect of watershed partitioning on calibrated hydrologic parameters of each subbasin using the peak-weighted root mean square error method as an objective function and the hydrograph at the outlet of the whole basin. It is found out that as the geometric magnitudes of the subbasins changed, the calibrated values of the hydrologic parameters of those subbasins changed as well. Then, a neighbouring basin, Kocanaz, is considered as an assumed neighbouring ungauged basin to investigate the effect of watershed partitioning of a gauged basin on the estimation of hydrograph of a neighbouring ungauged basin. Hydrologic parameters and direct runoff hydrograph of assumed ungauged neighbouring basin are estimated from the hydrologic parameters of the HEC-HMS calibration results of Gokirmak. Statistical indicators of the simulation results for each basin partitioning were graded with respect to the boundary values of the simulation outputs to find the best alternative. The grading results show that the simulation results with a single basin gave better representation among all other partitioning except two flood events.  相似文献   

Seismic hazard assessment and rheological implications: a case study selected for cities of Saudi Arabia along the eastern coast of Red Sea     

Faisal Rehman  Abdullah M. Alamri  Sherif M. El-Hady  Hussein M. Harbi  Ali H. Atef 《Arabian Journal of Geosciences》2017,10(24):540

A probabilistic approach is used to evaluate the seismic hazard for 12 strategic cities in Saudi Arabia along the eastern coast of Red Sea. The focal depth variations controlled by rheological characteristics are taken into account for hazard calculations, and its creditability is tested through sensitivity analysis for hazard results. This study presents a neo-probabilistic seismic hazard assessment methodology in which the focal depth distribution of earthquakes within seismogenic layer is divided into three depth slices. These depth slices are based upon rheological characteristic of seismogenic layer. The hazard results are obtained using this depth-slice methodology and conventional approach in which uniform distribution of seismicity within seismogenic layer is assumed. The sensitivity analysis culminated in underestimation of hazard values in higher frequencies for uniform distribution of seismicity within seismogenic layer. Foregoing the observations recorded above, it can be concluded that the exploitation of depth-slices biased by the rheology to calculate hazard is relatively preferable in the situations demanding safety measures.  相似文献   

Combination of GIS and mathematical modeling to predict floods in semiarid areas: case of Rheraya watershed (Western High Atlas,Morocco)     

Abdelhafid El Alaoui El Fels  Ali Bachnou  Noureddine Alaa 《Arabian Journal of Geosciences》2017,10(24):554

The Tinitine sub-watershed of Rheraya is renowned for its semiarid climate, irregular supply of water flow, and its historical floods; for these reasons, it is classified as vulnerable areas during a rainfall event. We conducted this study to propose flood prediction models adapted to this risky zone. For this, a hydrological method of flood forecasting rainfall-runoff used to determine a model conforms to the semiarid basin. This model is based on the articulation of the series production and transfer function. The goal of the production function is to determine the portion of the rainfall runoff, which is performed by two approaches that differ in their structures: (1) the first approach is based on the mathematical model of Horton; (2) the second approach is based on the determination of the part of the rain contributes to runoff and obtained by a spatial map of runoff coefficient (GIS). The transfer function is based on the two models of Clark and Nash, rainy efficient routes to the catchment outlet from a unit hydrograph. The characteristic parameters of these models are obtained through the application of mathematical optimization methods such as genetic algorithms. Thereby, the coupling function producing Horton (identified by the parameters: initial infiltration?=?15.03, final infiltration?=?0.3, and phi?=?0.45) and Clark transfer function (identified by the parameters C_A?=?0.21 and C_B?=?0.79) was given very satisfying results, mainly the low difference between observed and simulated hydrograph and Nash coefficient which is about 85%. This shows the interest of this coupling model in flood forecasting.  相似文献