摘要： 北非地区Ghadames盆地已成为中国海外油气勘探与项目投资的重点盆地之一,对其早古生代沉积体系及岩相古地理特征的准确认识是进一步勘探的基础,也是建立盆地早期构造与沉积演化过程的关键。以Ghadames盆地早古生界为研究目标,利用岩心、地震与测井等资料综合分析,开展古地貌恢复,对沉积体系、岩相古地理演化特征进行探讨。结果表明,Ghadames盆地早古生代共发育4种沉积体系: 冲积扇、辫状河、辫状河三角洲和浅海。早中寒武世,阿瓦隆地体向波罗的板块漂移,原特提斯洋初步扩张,形成活动大陆边缘,盆地以陆相沉积为主; 奥陶纪,盆地经加里东运动初步形成台内隆坳格局,Ghadames盆地西部和北部大范围剥蚀,冰川大规模出现,发育冰碛岩; 早中志留世,古特提斯洋持续扩张,海平面不断上升,盆地北部发生大规模海侵,以浅海沉积环境为主,广泛发育放射性页岩与泥岩,是区域内重要的烃源岩与盖层; 泥盆纪,海西运动使区域整体抬升,盆内海域范围减小,以陆相沉积为主。在此基础上,建立Ghadames盆地早古生代特提斯洋演化背景下的海陆过渡沉积模式,可为研究区下一步勘探工作提供参考依据。

关键词: 沉积体系, 岩相古地理, 沉积模式, 早古生代, Ghadames盆地, 北非地区

Abstract: The Ghadames Basin has become one of the significant basins for overseas exploration and project investment in China. Accurate understanding of the early Paleozoic sedimentary system and lithofacies palaeogeographic characteristics is the basis for further exploration and the key to establish the early tectonic-sedimentary evolution history of the basin. Based on the comprehensive analysis of core,seismic and logging data in Ghadames Basin,combined with the restoration of palaeogeomorphology,the sedimentary system and lithofacies palaeogeographic characteristics are discussed. The results show four types of depositional systems in the early Paleozoic of Ghadames Basin: alluvial fan,braided river,braided river delta and shallow marine. In the early and middle Cambrian,the Avalon terrane drifted toward the Baltic plate,the Proto-Tethys Ocean initially expanded,and the active continental margin was formed. During this period,the whole basin was dominated by continental deposits. During the Cambrian-Ordovician,the platform uplift and depression pattern was initially formed owing to the Caledonian movement. Large-scale denudation occurred in the western and northern parts of the Ghadames Basin,and large-scale glacier deposits were developed to form glacial moraine reservoirs. In the Early and Middle Silurian,the Palaeo-Tethys Ocean continued to expand,the sea level rose,and a extensive transgression occurred in the northern part. Shallow marine sedimentary environment predominated in the area during this time,and hot shale and mudstone were widely developed which are important source rocks and cap rocks in the region. In the Devonian period,the Hercynian movement uplifted the region as a whole,and the sea area in the basin was reduced and replaced mainly by continental sediments. On this basis,the establishment of the marine-continental transition sedimentary model under the early Paleozoic Tethys Ocean evolution background in the Ghadames Basin is established,which can provide a reference for the next exploration work in the study area.

Key words: depositional system, lithofacies palaeogeography, sedimentary model, Early Paleozoic, Ghadames Basin, North Africa

中图分类号: 

• P531