摘要
林家组出露于辽宁东部本溪林家崴子一带.自小林贞一1942年记载以来,其时代一直有很大的争议.争议跨度从第三系到上二叠统.20世纪80年代初,张武等依据动植物化石和地层对比,提出了林家组属于中三叠世的观点.由于林家组产出的植物化石十分复杂,既有古生代,又有中生代分子,且没有锆石年龄证据,故林家组时代仍然存疑.近年来,在林家组底部找到了变质凝灰质粉砂岩,其中有很多锆石.根据30颗保存较好锆石测年结果,发现4颗最年轻锆石的^206Pb/^238U平均年龄是239.5±4.1 Ma.另外,最近前甸子地区林家组发现了少林肋木(Pleuromeia shaolinii).因此尽管林家植物群存在二叠纪和三叠纪均有分布的重要植物,但结合锆石定年、地层对比、岩性特征、平行不整合接触关系、三叠纪代表植物及中三叠世到早白垩世均有分布的昆虫索德蠊属来综合分析,可以确认林家组确实属于中三叠世.
The Linjia Formation is outcropped in Linjiawaizi area,Benxi,eastern Liaoning Province.Since recorded by Kobayashi in 1942,its age has long been a great controversy.In the early 1980s,Zhang et al.suggested that the Linjia Formation should be assigned to Middle Triassic on the basis of the plant fossils fish scales,insect wings,spores and pollens,as well as stratigraphic correlation.As the components of Linjia flora are very complicated with both Paleozoic and Mesozoic elements but without evidences of zircon ages,the age of Linjia Formation has not yet been determined Recently,the metamorphic tuffaceous siltstones containing lots of zircons were found at the bottom of Linjia Formation.According to the dating results of 30 grains of zircon crystal,the average ^206Pb/^238U age of 4 newest zircons was 239.5±4.1 Ma.In addition,Pleuromeia shaolinii was lately discovered from Linjia Formation in Qiandianzi area.Although some significant fossil plants of Linjia flora are distributed striding cross Permian and Triassic,combined with the zircon dating,stratigraphic correlation,lithologic characteristics,parallel unconformity relation,typical Triassic fossil plants and the Middle Triassic-Early Cretaceous insect fossil Sogdoblatta,it is confirmed that the Linjia Formation belongs to Middle Triassic.
作者
张宜
郑少林
李之彤
曹成润
杨佳林
张国仁
李显东
孟繁巍
ZHANG Yi;ZHENG Shao-lin;LI Zhi-tong;GAO Cheng-run;YANG Jia-lin;ZHANG Guo-ren;LI Xian-dong;MENG Fan-wei(College of Paleontology,Shenyang Normal University,Shenyang 110034,China;Key laboratory for Evolution of Past life in Northeast Asia,Ministry of Natural Resources,Shenyang 110034,China;Shenyang Center of Geological Survey,CGS,Shenyang 110034,China;Liaoning Institute of Geological Exploration Co.,Ltd.,Dalian 116100,Liaoning Province,China;Nanjing Institute of Geology and Palaeontology,Chinese Academy of Sciences,Nanjing 210008,China)
出处
《地质与资源》
CAS
2019年第5期434-442,共9页
Geology and Resources
基金
国家自然科学基金项目“辽宁本溪中三叠世林家植物群系统研究”（编号31470324）
中国地质调查局项目“辽宁1∶5万鞍山、大孤山幅区域地质调查”（编号DD20190042-01）
关键词
锆石U-PB年龄
肋木属
索德蠊属
林家组
中三叠世
辽宁本溪
zircon U-Pb age
Pleuromeia
Sogdoblatta
Linjia Formation
Middle Triassic
Benxi of Liaoning Province
