云南香格里拉上三叠统沉积混杂岩中的晚古生代和中三叠世放射虫及其地质意义  

LATE PALEOZOIC AND MIDDLE TRIASSIC RADIOLARIA FROM THE UPPER TRIASSIC SEDIMENTARY MLANGE IN SHANGRILA, SOUTHWEST CHINA AND ITS GEOLOGICAL SIGNIFICANCE

作　　者：谢力[1,2] 杨文强[3] 刘桂春 冯庆来[2] 

机构地区：[1]中国地质大学地质博物馆,北京100083 [2]中国地质大学地质过程及矿产资源国家重点实验室,武汉430074 [3]武汉地质调查中心(武汉地质矿产研究所),武汉430223 [4]云南省地质调查院,昆明650011

出　　处：《微体古生物学报》2012年第3期253-269,共17页Acta Micropalaeontologica Sinica

基　　金：国家自然科学基金(41172202);地质过程与矿产资源国家重点实验室基金项目共同资助

摘　　要：香格里拉地区位于义敦弧后盆地与中咱地块的过渡带,出露的地层主要为上三叠统哈工组、图姆沟组。其中,哈工组发育大量的沉积混杂岩。笔者从硅质混杂岩块中分离出保存完好的放射虫化石。这些放射虫化石分异度较高,主要有内射虫目、泡沫虫目、罩笼虫目和少量隐管虫目、阿尔拜虫目的放射虫。本文报道了其中的内射虫目、泡沫虫目、罩笼虫目和隐管虫目放射虫共计50种27属。这些放射虫的地质时代自中泥盆世至中三叠世。因为沉积混杂岩中的硅质岩块源自甘孜理塘构造带,这些保存较好的放射虫化石为解释甘孜理塘构造带的构造演化提供了必需的地质时代证据。根据这些放射虫组合所代表的深水环境,我们认为甘孜-理塘构造带所代表的沉积盆地自中泥盆世至中三叠世时期应为深水盆地,也即德格-中甸微板块在中泥盆世时期就已逐渐与扬子板块裂离。Shangrila area is located paleogeographically at the transitional zone between the Yidun back-arc basin and the Zhongza block represented by the Upper Triassic Hagong Formation and Tumugou Formation. The sedimentary mélange composed of the exotic siliceous blocks with minor limestone and sandstone blocks occurs mainly in the Upper Triassic Hagong Formation. Moderately well-preserved radiolarians were collected recently from the exotic siliceous blocks within the sedimentary mélange of the Upper Triassic Hagong Formation. These radiolarians, characterized by high diversity, include spumellarians, entactinarians, latentifistularians and albaillellarians. Among them, 50 species of Spumellaria, Entactinaria, Nassellarina, and latentifistularians belonging to 27 genera are taxonomically analyzed. The radiolarian faunas apparently indicates the Middle Devonian to early Middle Triassic ages. Because the siliceous blocks within the sedimentary mélange originated in the Garze-Litang tectonic belt, the successful recovery of the well-preserved radiolarians provides the age constraints necessary for the interpretation of the tectonic development of the Garze-Litang tectonic belt. On the basis of the deep-water settings indicated by the species composition of radiola-rian fauna, we suggest that the sedimentary basin, represented by the Garze-Litang tectonic belt, became a deep-water basin during the Early Carboniferous to Middle Permian and hence, the Dege-Zhongdian microplate must have been gradually separated by rifting from the Yangtze Plate before the Early Carboniferous.

关 键 词：放射虫 沉积混杂岩 生物地层学 晚古生代 中三叠世 甘孜理塘构造带 香格里拉 云南 

分 类 号：Q915[天文地球—古生物学与地层学]