闽西南地区晚三叠-早侏罗世温湿-干热气候转变的沉积记录

Sedimentary records of the climatic transition from warm and humid to dry and hot during Late Triassic-Early Jurassic in Southwestern Fujian

本文对闽西南地区南靖油柑坪剖面文宾山组,漳平西园和漳平高明坑剖面梨山组粉砂质泥岩、凝灰质泥岩和泥岩样品进行了全岩分析和ICP-MS微量、稀土元素测试,综合元素含量及有关比值的变化,结合岩性、岩相和古生物特征,分析了闽西南地区晚三叠世文宾山组、早侏罗世梨山组沉积时的古气候特征.提出了闽西南地区晚三叠世以温湿气候为主,可能出现短暂炎热气候;早侏罗世以温湿气候为主,早侏罗世晚期气候较晚三叠世和早侏罗世气候要干燥炎热的观点.研究结果表明:闽西南地区南靖油柑坪剖面文宾山组、漳平西园剖面梨山组和漳平高明坑剖面梨山组Ca元素富集系数(0.16,0.44,0.25),AI2O3富集系数(1.35,1.11,1.30)、m值(2.02～2.71,2.24～11.38,2.86～4.46),Mg/Ca比值(0.35～2.39,0.23～3.57,0.55～0.80)在湖泊相和海相环境中均能敏感的反映古气候的变化;南靖油柑坪剖面文宾山组Sr/Cu(1.09～7.02),Fe/Mn(79～201.5),δCe(0.63～1.41)和δEu(0.69～0.90)值在湖泊环境中对古气候的反映敏感,岩石地球化学元素含量及其比值、组合的变化在一定程度上指示着古气候演化历程.

Samples were selected from silty mudstones, tuffaceous mudstones and mudstones of Wenbinshan formation in Nanjing Youganping, Lishan formation in Zhangping Xiyuan and Zhangping Gaoming areas, and were subjected to whole rock analysis, and ICP-MS trace and rare earth elements tests. Based on element contents and ratio changes, and combined with the lithological, facies and paleontological features, the paleoclimatic sedimentary characteristics of the Wenbinshan formation at late Triassic and Lishan formation in early Jurassic were studied. Climate in late Triassic was dominated by warm and humid climate and hot weather may have been short. The climate in early Jurassic was dominated by warm and humid climate and in lat- er early Jurassic was drier and hotter than in late Triassic and early Jurassic. The enrichment factors such as Ca （0.16, 0.44, 0.25）, AI203 （1.35, 1.11, 1.30） and the m values （2.02-2.71, 2.24-11.38, 2.86-4.46）, and the Mg/Ca ratios （0.35-2.39, 0. 23-3. 57, 0.55- 0.80） in lacustrine and marine environments in Wenbin shan formation in Nanjing Youganping area and Lishan formation in Zhangping Xiyuan and Zhangping Gaoming area in Southwestern Fujian can be used to reflect the paleoclimatic changes. In Wenbin shan formation in Nanjing Youganping area, the values of Sr/Cu （1.09-7.02）, Fe/Mn （79-201.5）, Ce （0.63-1.41） and Eu （0.69-0.90） reflect the paleoclimatic sensitivity in the lake environment. The con-tents, ratios and combinations of the geochemical elements indicate the evolution history of pa- leoclimate to some extent.