【摘要】 <正> 塔里木盆地中新世地层分布广泛,地表露头和钻井揭露所得资料表明,位于天山前和昆仑山前拗陷中为一套厚度达数千米的碎屑沉积。这套地层不仅厚度大、分布广,且与寻找油气矿藏有着直接关系,为本区石油找矿的目的层之一。本文对盆地北缘、西缘和西南缘十七个地点中新世有孔虫化石的鉴定结果作了分析,对中新世有孔虫群的特征及其地质意义进行了讨论。文中所用化石标本大部分由新疆石油局南疆指挥部化验室提供,一部分由笔者和他们共同采集,化石图版由中国地质科学院地质研究所胡昀、杨安国同志扫描照更多还原

【Abstract】 The miocene beds in Tarim Basin are characterized by variegated clasticdeposits comprising mainly sandstone, siltstone, arenaceous mudstone and mu-dstone with intercalations of gypsum and occasionally of conglomeratic beds.The whole sequence is predominated by dark brownish, brownish, reddish andyellowish strata intercalated with subordinate dark grey, grey and greyishgreen beds. Gypsum deposits are better developed in the middle and lowerparts. Miocene deposits are widespread in bordering areas of the basin alongthe piedmont belt of Tianshan and Kunlun mountains. Materials studied bythe writers are mainly collected from the Kashi depression, the Southwestdepression and the Kuqa depression. Subdivision of Miocene strata in thesedepressions and correlation between them are given in table 1. Fossil foraminifera are collected from 17 localities, among which threefaunas are distinguished. 1. The Oligocene-Miocene fauna in Wulukeqiate and Keziloyi from thelower part of Keziloyi Formation consists mainly of Cibicidoides ovaliformis,C. amygdaliformis, Pullenia quinqueloba, Melonis sp., Nonion sp. and Cibicidessp.. This fauna is poorly developed with low diversity and small population.Since most of the species are indigenous and abundant in the underlyingEocene and Oligocene strata, the exact age of the fauna is in dispute. 2. The Miocene Ammonia fauna occurs in abundance and wide distribu-tion in two west-east stretching areas, the one from Wuqia to Xiao’atushiin Kashi depression. while the other from Kuqa river to Kurle in Kuqadepression. Important elements of the fauna include Ammonia beccarii(Linne),A. limnetes (Todd et Bronnimann), A. honyaensis(Asano), A. tepida(Cushman), A. hatatatensis (Tokayangi), A. multicella S. Y. Zheng. The less abundantelements are Ammonia convexidorsa Zheng and A. mineacea (Bermudes). Inassociation with them only very few species of Cibicides and Nonion havebeen found in small amount. Individuals of each Ammonia species are numerous and dwarfish withless whorls and chambers than those of the normal marine forms. Malformedindividuals are often encountered. Appearing in association with this fauna is an assemblage of Ostracodspredominated by typical brackish species Cypridies littoralis and some fresh-water forms which tolerate the oligohaline to brackish environment, suchas Cyprinotus deformis and Limnocythere argulata. Very few oogonia of cha-rophytes occur in association with this fauna. This fauna ranges from Anju’an Formation to the lower part of Paka-bulake Formation, the age of which is assigned to Middle to Late Miocene. 3. The Miocene non-Ammonia fauna is characterized by the absence ofAmmonia. It is infertile and represented by a few shallow marine taxa, suchas Cibicidoides ovaliformis, C. amygdaliformis, C. spp., and Asterigerind sp.from the middle Miocene beds in Wulukeqiate as well as Pararotalia armata,P. spp., Eponides spp., Nonion sp. and Anomalina sp. from the middle partof Wuqia group in Qimugen. The age of this fauna belongs to Middle Miocene. As indicated by the development and distribution of the Ammonia faunaand the non-Ammonia fauna (fig. 1), two different environments of deposi-tion might have existed in Tarim Basin during the Middle Miocene time. 1)Brackish water environment along the coast; 2) Near-shore shallow marineenvironment which might have more direct connection with the open sea. Abrief analysis of these environments and discussion of their bearing on oilaccumulation are made in the present paper.更多还原