【摘要】 <正> 塔里木盆地位于天山和昆仑山两个古生代褶皱带之间,是在塔里木地台的基础上发展起来的中新生代断陷盆地。塔里木盆地蕴藏有丰富的油气和盐类矿产资源。本区中新生代海相地层与这些矿产的关系尤为密切。进行这段地层层序及其沉积环境的研究,对于弄清晚白垩世到第三纪塔里木西部的基础地质问题和沉积矿产的生贮规律与远景评价都具有重要意义。本文根据近年来野外和室内工作中积累的材料,主要运用有孔虫化石在各层段地层中的分布规律及其生态特征对西塔里木中新生代海湾的发生、发展和终结更多还原

【Abstract】 This paper deals with the origin and evolution of the West Tarim Gulf and the change from a gulf to a terrestrial basin in Meso-Cenozoic time on the basis of stratigraphic and geographic distribution as well as ecologic features of the foraminifers found in the strata from the Upper Cretaceous to the Tertiary in the western part of the Tarim Basin.As a result of the eastward invasion of the Tethys Sea in Late Mesozoic, a bag-like gulf was formed in the western part of the Tarim Basin. Since then, a stable shallow sea environment remained in the gulf for a long time,this can be well interpreted by the Late Cretaceous strata composed mainly of argillaceous deposits with an aboundant shallow marine biota including echinoids, ammonites, marine bivalves, gastropods, ostracods, foraminifers, coccolithids, dinoflagellats, etc. Many of these organisms had close affinities to those inhabiting the open sea to the west of the gulf, indicating a fluent connection between the gulf and the sea. The foraminiferal fauna developed at that time comprised mainly agglutinate forms dominated by Migros and Ammobaculites, while planktonic forms occurred only in the western part, i. e., near the outlet of the gulf. In late Late Cretaceous,the water became shallower and littoral lagoons developed in the gulf.In Early Tertiary, the marine transgressive area enlarged gradually. In Early Palaeocene, the gulf almost became a lagoon harbor, the environment was favorable for the formation of evaporites, and therefore widespread gypsum beds attaining a total thickness of 300 m were deposited. In Middle to Late Palaeocene, the gulf resumed its shallow marine environment with normal salinity and received mainly argillaceous sediments, whiles organisms rapidly became thriving, with some important groups such as ostrea,other marine bivalves, gastropods, crinoids, ostracods, foraminifers, algae, etc. The foraminfers were comparatively abundant, represented by the SpiroplectamminaGlobigerina-Nonionellina fauna. The distribution of planktonic foraminifers was restricted to the western part of the gulf. From Early to middle Late Eocene, the gulf had undergone another cycle of development from a littoral lagoon to a normal neritic environment. The forarniniferal Nonion-Cibicicles-Anomalinoides fauna occurring in middle Late Eoce consisted almost exclusively of benthonic forms with calcareous perrotate tests, and no planktonic forms have ever been found in this fauna.At the end of Eocene, a littoral-lagoon environment resumed once again in the gulf, but it gradually changed to a normal neritic environment toward Early Oligocene, during which sediments mainly of argillaceous and arenaceous substance accumulated, while marine bivalves, gastropods, echinoids, ostracods, foraminifers and algae thrived in the western part of the gulf. The foraminifers were represented by the Cibicidioides fauna and dominated by calcareous perforate forms, but the planktonic forms existed only near the outlet of the gulf.At the end of Oligocene the eastward stretch of the Tethys Sea became enclosed due to the effect of the regional tectonic movement. The connection of the West Tarim Gulf with the sea was completely cut off and desalination of the gulf water began to take place. In Miocene,the foraminifers almost disappeared in the gulf area. only a brackish water Ammonia biofacies in the Kuzgongsu region and a normal marine Cibicidoides biofacies in the northwestern part of the gulf have been found so far. The gulf probably became an inland basin and began to receive terrestrial deposits in Miocene.更多还原