Charophyte biostratigraphy of the non-marine Lower Cretaceous in the Central Tunisian Atlas (North Africa): Palaeobiogeographic implications     

《Cretaceous Research》2016

The chronostratigraphic framework of the non-marine deposits of the Central Tunisian Lower Cretaceous (Kebar Formation) is reviewed from a biostratigraphic viewpoint. The outcrops located in the Jebel Kebar, Jebel Ksaïra and Jebel Koumine localities provided charophyte assemblages belonging to two biochronozones: Ascidiella cruciata-Pseudoglobator paucibracteatus (upper Barremian–lower Aptian) and Clavator grovesii lusitanicus (upper Aptian–lower Albian). Clavatoraceans from the upper Barremian–lower Aptian in the Tunisian Atlas are reported here for the first time. The assemblage consists of Atopochara trivolvis var. triquetra, Ascidiella iberica var. inflata, Globator maillardii var. trochiliscoides, Globator maillardii var. biutricularis, Echinochara peckii var. lazarii, Clavator harrisii var. harrisii and Clavator harrisii var. reyi. In addition, a new characean species, Mesochara magna nov. sp. Trabelsi and Martín-Closas, is described herein. The results show that the Kebar Formation is diachronous in Central Tunisia, with a more complete record to the north (Jebel Koumine) than in the type locality (Jebel Kebar). Barremian–Aptian diapiric activity is proposed as the factor that controls the diachronous nature of this formation.The late Barremian–early Aptian charophyte assemblages from the Kebar Formation display strong affinities with the contemporaneous floras of the European basins, thus suggesting that intense supraregional floristic exchanges occurred between the Tethyan islands scattered throughout what is now Western Europe and North Africa. The biogeographic distribution of these charophytes leads to the hypothesis that the peri-Tethyan Archipelago acted as an effective bridge for the intercontinental exchanges of these plants between Laurasia and Gondwana.  相似文献   

湖北省行政区划图集的设计思想     

何丽华  徐汉卿 《地理空间信息》2010,8(3):128-130

为社会经济发展全面布局、统筹规划与宏观决策提供重要科学依据,将权威、法定的区划、地名和界线信息以地图形式直观地显示,湖北省首次开展了《湖北省行政区划图集》编制工作。在图集设计工作中,围绕使用资料权威性、内容表达系统性和图面形式艺术性主题,对图集内容、编排、配置、工艺、色彩及符号等环节进行了大量设计实践工作,创新表达了图集结构、表示方法、整饰等方面,为区域行政区划图集设计探索了工作思路,并可向同类型地图集设计提供技术经验。  相似文献   

特征数据模型在《南极赛博地图集》数据描述中的应用   总被引：1，自引：0，他引：1  

张春奎  庞小平  鄂栋臣 《测绘与空间地理信息》2006,29(1):7-10

地理特征是地球空间上客观存在、具有描述信息的地理实体。特征数据模型倾向于对地理实体的概念描述,它从几何分布、专题要素与时态变化三个方面来描述地理特征,能够实现语义层次上的数据共享。这对于以数据共享和地图制图为主要目的的《南极赛博地图集》来说,能够很好地对南极数据进行抽象和概括。因此,本文就如何利用特征数据模型对地图集中的南极数据进行描述作了阐述。  相似文献   

Neotectonics and associate seismicity in the Eastern Tellian Atlas of Algeria   总被引：2，自引：1，他引：1  

A. Harbi  S. Maouche  A. Ayadi 《Journal of Seismology》1999,3(1):95-104

Seismicity in the Eastern Tellian Atlas of Algeria is active of moderate to low magnitude. The direct identification of active fault is often a difficult task. In fact, in this region, despite the intense seismicity, only the Constantine earthquake of 27 October, 1985 ( M s = 5.7) and the Kherrata earthquake of 17 February, 1949 ( M s = 4.7), have generated surface ruptures. Hence, the integration of both geological, historical and instrumental seismic data are important in order to characterise the most important seismogenic structures. This paper presents a preliminary overview of the identified neotectonic faults that we consider active in the Eastern Tellian Atlas of Algeria. Thus, seismicity and neotectonic maps are presented and the faults which are active or potentially active from a neotectonic point of view are shown in relation with the main seismic groupings. This study based mainly on available seismic and bibliographic data and several unpublished marine seismic data enable us to suspect a fault as the eventual source of the Jijeli earthquake of 21 August 1856 that destroyed the Jijeli town and its surroundings. The results inferred from this work represent a starting point for more detailed studies in seismogenic areas.  相似文献   

Two complimentary and integrated land uses of the western High Atlas Mountains, Morocco: the potential for sustainable rural livelihoods     

C. J. Barrow  H. Hicham 《Applied geography (Sevenoaks, England)》2000,20(4)

This paper examines the status of traditional agriculture in two areas of Azilal province in the Atlas Mountains, seeking to identify what is needed to counter any breakdown in livelihood strategies and improve the quality of life enjoyed by the farmers. Irrigated terrace agriculture is an important part of livelihood strategies in the areas studied and has the potential to be more productive and sustainable. In some areas it is reported to be endangered by socioeconomic changes and highland land degradation caused by excessive shifting cultivation, sheep and goat grazing, and charcoal production. Field visits made during summer 1998 to establish the condition of irrigated terrace and runoff agriculture and the factors affecting it showed that in at least one of the villages supportive social capital has ensured that challenges are being met and beneficial innovations are being made. Considerable variation in success was evident from community to community, with some farmers maintaining adequate lifestyles and innovating, while in other communities prospects are less promising. The effects of structural adjustment have clearly been felt and may also have triggered some of the highland degradation and difficulties, which clearly threaten some irrigated terrace agriculture and other livelihood practices.  相似文献   

俄罗斯可持续发展地图集信息系统——现状和应用前景     

伏拉季米尔·谢尔盖耶维奇·吉库诺夫 《地球信息科学学报》2003,5(3):112-117

分析了人类发展向可持续发展模式过渡的必然性 ,指出必须适合俄罗斯现实的人类发展指标。阐述周围环境及确定俄罗斯达到可持续发展途径及可能的指标 ,强调在建立国土可持续发展模式时历史观点的重要性。分析了俄罗斯可持续发展地图集结构的特征。  相似文献   

中国之窗——地图大系的北京旅游系列电子制图模块的设计研制     

傅俏梅 《地球信息科学学报》2001,3(2):34-37

本文重点讨论了中国之窗-地图大系的北京旅游系列电子制图的设计思路及其研制的技术方法。概要介绍了其组成的6个子模块功能与应用特点。同时提出旅游信息系统发展的趋势。  相似文献   

Areas of the global major river plumes     

KANG Yan  PAN Delu  BAI Yan  HE Xianqiang  CHEN Xiaoyan  CHEN Chen-Tung Arthur  WANG Difeng 《海洋学报(英文版)》2013,32(1):79-88

River plumes are the regions where the most intense river-sea-land interaction occurs, and they are characterized by complex material transport and biogeochemical processes. However, due to their highly dynamic nature, global river plume areas have not yet been determined for use in synthetic studies of global oceanography. Based on global climatological monthly averaged salinity data from the NOAA World Ocean Atlas 2009 (WOA09), and monthly averaged salinity contour maps of the East and South China Seas from the Chinese Marine Atlas, we extract the monthly plume areas of major global rivers using a geographic information system (GIS) technique. Only areas with salinities that are three salinity units lower than the average salinity in each ocean are counted. This conservative estimate shows that the minimum and maximum monthly values of the total plume area of the world’s 19 largest rivers are 1.72 × 10 6 km 2 in May and 5.38 × 10 6 km 2 in August. The annual mean area of these river plumes (3.72 × 10 6 km 2 ) takes up approximately 14.2% of the total continental shelves area worldwide (26.15 × 10 6 km 2 ). This paper also presents river plume areas for different oceans and latitude zones, and analyzes seasonal variations of the plume areas and their relationships with river discharge. These statistics describing the major global river plume areas can now provide the basic data for the various flux calculations in the marginal seas, and therefore will be of useful for many oceanographic studies.  相似文献   

Spatial soil loss risk and reservoir siltation in semi-arid Tunisia     

Sihem Jebari  Ronny Berndtsson  Akissa Bahri  Mohamed Boufaroua 《水文科学杂志》2013,58(1):121-137

Abstract

Soil erosion vulnerability and extreme rainfall characteristics over the Mediterranean semi-arid region of Tunisia are crucial input for estimation of siltation rate in artificial reservoirs. A comprehensive high-resolution database on erosive rainfall, together with siltation records for 28 small reservoirs, were analysed for this region, the Tunisian Dorsal (the easternmost part of the Atlas Mountains). The general life-span of these reservoirs is only about 14 years. Depending on the soil degradation in the different catchments, the corresponding reservoirs display a wide range of soil erosion rates. The average soil loss was 14.5 t ha^?1 year^?1 but some catchments display values of up to 36.4 t ha^?1 year^?1. The maximum 15-min duration rainfall intensity was used to determine the spatial distribution of rainfall erosivity. The northwestern parts of the Tunisian Dorsal display the most extreme rainfall erosivity. Spatial erosion patterns are to some extent similar; however, they vary greatly according to their location in the “soil degradation cycle”. This cycle determines the soil particle delivery potential of the catchment. In general, the northwestern parts of the Dorsal display modest soil erosion patterns due to the already severely degraded soil structure. Here, the soil surface is often the original bedrock. However, the greatest soil erosion occurs in the mid-eastern parts of the Dorsal, which represents the “degradation front”. The latter corresponds to the area with highest erosion, which is continuously progressing westward in the Dorsal. The large variation between the erosive rainfall events and the annual soil loss rates was explained by two important factors. The first relates to the soil degradation cycle. The second factor corresponds to the degradation front with the highest soil loss rates. At present this front is located at 300 m altitude and appears to be moving along an 80-km westward path starting from the east coast. A better understanding of the above can be used to better manage soils and soil covers in the Tunisian Dorsal area and, eventually, to decrease the soil erosion and reservoir siltation risk.

Citation Jebari, S., Berndtsson, R., Bahri, A. & Boufaroua, M. (2010) Spatial soil loss risk and reservoir siltation in semi-arid Tunisia. Hydrol. Sci. J. 55(1), 121–137.  相似文献   

Mode de mise en place des corps salifères dans l'Atlas septentrional de Tunisie. Exemple de l'appareil de Bir Afou     

Mohamed Ben Chelbi  Fetheddine Melki  Fouad Zargouni 《Comptes Rendus Geoscience》2006,338(5):349-358

30 km southwest of Tunis, two thin flaky ‘Triassic’ intrusions underline the two flanks of the Atlasic anticline of Bir Afou. These evaporites are interbedded within the Clansayesian shales, and are under and overlain by glauconitic conglomeratic contacts. The ‘Triassic’ flakes, topic of our study, are sourced from the Bir Afou Triassic mass after a rapid pouring out during Late Aptian extensional tectonics. This structure corresponds, for us, to a ‘salt glacier’, similar to that one described at Ben Gasseur by Vila and al. [J.M. Vila, M. Ben Youssef, M. Chikhaoui, M. Ghanmi, Bull. Soc. géol. France 167 (1996) 235–246], which was subsequently folded during Lower Eocene times. Middle and Upper Eocene transgressive formations unconformably deposited on top of the Aptian anticlinal hinge. The major Late Miocene compressive phase is responsible for the present structures and that are superimposed onto the pre-existing ‘salt glacier’. This salifereous system extends the ‘salt glacier’ domain towards the eastern part of the Tunisian Atlas. To cite this article: M. Ben Chelbi et al., C. R. Geoscience 338 (2006).  相似文献