摘要
云南西部施甸泥盆纪疑缘类研究对重建该地区泥盆纪古地理和沉积环境有十分重要的意义.首次报道了云南西部保山地区施甸泥盆纪疑缘类21属35种.根据疑缘类特征及其在地层中的分布和演化规律,自下而上可以划分2个疑缘类组合带:相当施甸何元寨剖面的西边塘组上部泥岩段的疑缘类组合带;马鹿塘疑缘类组合带.该区的疑缘类可与国内外同时代的疑缘类比较.微古植物(疑缘类)和孢子含量的比例关系及其特征性的属种证明,西边塘组属正常浅海沉积,马鹿塘组较西边塘组略深,为陆棚浅海沉积.
With only minor exceptions, the palaeoenvironmental interpretation based on microphytoplankton diversity and microphytoplankton/spore ratios is in agreement with previous ecological and depositional interpretation for the Xibiantang Formation ( Late Early Devonian, Emsian - Eifelian) and Malutang Formation (Middle Devonian, Givetian)in Shidian County, Western Yunnan, China. Analyses of acritarchs mor-photype variability, fluctuations in acritarch species diversity and the ratio of microphytoplankton (Acritarchs and Prasinophytes) to spores were compared with known palaeoenvironmental interpretation based on sedimentology and megafossil content .The two distinct stratigraphically successive acritarchs assemblages are discernible.The Xibiantang Formation acritarch assemblage is characterized by the abundant appearance of Cy-matiosphaera reticulosa (Kiryanor) Colbath, C. cornifera Deunff, C. magnata Pichler, Polyedryxium camatum Playford, P. decorum Deunff, Comasphaeridium muscosum Wicander et Playford, Multiplici-sphaeridium sp., Dictyotidium variatum Playford, D. cf. torosum Playford, Gorgonisphaeridium con-densum Playford, Lophosphaeridium segragum Playford, Melikeriopolla venulosa Playford, Navifusa ba-cillum (Deunff) Playford, N . exilis Playford, Micryhastridium stellatum Deflandre, Maranhites gallicus Tangaurdeau - Lant, Tasmanites sp. .The acritarch assemblage of the Malutang Formation is marked by appearance of Chomotriletes revu-gensis Naumova, Tunisphaeridium tentaculaferum( Martin) Cramer, Holosphaeridium microclavatum Play-ford, as well as a more constant occurrence of Dictyotidium cf. torosum Playford, Gorgonisphaeridium sp. cf. Micrhystridium sericum Deunff, ? Gneudunlla sp., Hapsidopolla exomata (Deunff) Playford, Lophosphaeridium dumalis Playford, Leiosphaeridia lavigata Stockmans et Williere, Veryhachium downiei Stockmans et Williere, Visbysphaera gotlandica (Eisenack) Lister, and few Chitinozoans and Scolec-odonts.The acritarchs of Western Yunnan may be correlated basically with those in South China, Western Europe, North America, Australia and North Africa.Analysis of fluctuations in the microplankton to spore ratio combined with changes in the morphotype composition and diversity of acritarch assemblage indicates that the Xibiantang Formation was intially deposited in a near- to normal shallow marine environment. The total microplankton of the Malutang indicates a shelf marine environment of deposition.
出处
《古地理学报》
CAS
CSCD
1999年第4期35-44,共10页
Journal of Palaeogeography：Chinese Edition
关键词
云南
泥盆纪
古环境
古地理
疑缘类
Acritarchs, Western Yunnan, Early Devonian, Middle Devonian, Palaeogeography, Pa-leoenvironment
