摘要
研究区属北羌塘盆地,上三叠统巴贡组呈NW向带状分布于长江源各拉丹冬地区南北两侧(以往南部称土门格拉组),夹于金沙江缝合带南侧和中央隆起带之间,南部土门格拉一带产Cardium(Tulongocardi-um)martini—Trigonia(Kumatrigonia)huhxilensis组合,北部雀莫错一带产Halobia superbescens—Halobia disper-seinsecta组合和Amonotis togtonheensis—Cardium(Tulongocardium)xizangensis组合,反映的地质时代为诺利期,但南北部双壳类组合优势种明显不同。本文从物源区、沉积岩石类型及其组合、高频旋回沉积和古盐度、古水深、古气候及岩石地球化学和古生物特征角度,探讨南北巴贡组沉积古地理格局和双壳类组合的古生态,提出南部双壳类组合生活在盐度较低、氧化、干热、弱碱性浅水环境并繁盛于海泛晚期—海退期层位中,陆源物质供应充分而物种分异度不高;北部双壳类生活在盐度稍高、弱还原、温暖潮湿的较深水环境并繁盛于海侵—高水位期层位中,生物群面貌上的差异是同一地质时期南北不同的沉积环境造成的。
The Bagong Formation of Upper Triassic in the northern Qiangtang Basin is distributed in the southern and northern sides of Geladandong area with a strap of northwest strike （ the southern part is named as the Tumengela Formation formerly ） , and tectonicly exists between the southern part of Jinshajiang suture belt and the middle uplift belt. Three assemblages have been recognized, among which one of the bivalves assemblages named Cardium （Tulongocardium） martini-Trigonia （Kumatrigonia） huhxilensis is recognized from the Tumengela area of the southern side, and the other two assemblages named Halobia superbescens-Halobia disperseinsecta assemblage and Amonotis togtonheensis-Cardium （ Tulongocardium） xizangensis assemblage from the Quemocuo area of the northern side have been established in this paper. Although these assemblages are considered as to be in the similar age as the early-middle Norian of Late Triassic, the predominant species of each assemblage are greatly different. Based on the investigations and analyses of the provenance, sediment-types, sedimentary features of high-frequency cycles,palaeosalinity, paleo-sea level, paleoclimate, lithochemical and trace element contents, as well as biotic characters, the palaeogeographical and paleoecological characteristics of the study region are discussed. It has been concluded that the bivalves with a relative lower specific diversity in the southern region lived in shallow-water environments with a lower salinity and oxidation and a higher evaporation and alkalescence; however, those in the northern region lived in deep-water sedimentary environments with a higher salinity and deoxidization and warm-humidity and flourished during the late period of the transgression and early period of the regression. These biotic differences between the northern and southern regions were caused by different sedimentary environments in the same geologic period.
出处
《古地理学报》
CAS
CSCD
2007年第1期59-68,共10页
Journal of Palaeogeography：Chinese Edition
基金
国家自然科学基金项目(40372004)资助
关键词
双壳类组合
上三叠统
巴贡组
沉积环境
古生态
长江源区
bivalves assemblages, Upper Triassic, Bagong Formation, sedimentary environments, paleoecology, Yangtze Source Region
