本文關(guān)鍵詞： 六盤山地區(qū) 地層時代 延安組 U-Pb同位素定年 再旋回化石　出處：《地學(xué)前緣》2017年05期 　論文類型：期刊論文

【摘要】：為正確劃分六盤山地區(qū)具"上三疊統(tǒng)或下-中侏羅統(tǒng)"之爭的中生代煤系地層,通過野外沉積現(xiàn)象觀察、鏡下礦物學(xué)研究并結(jié)合砂巖碎屑鋯石LA-ICP-MS U-Pb同位素定年,重新厘定了該套煤系地層的時代。六盤山地區(qū)爭議地層普遍發(fā)育鐵質(zhì)結(jié)核,砂巖差異風(fēng)化嚴(yán)重,這與鄰區(qū)下-中侏羅統(tǒng)延安組地層相似,而與鄰區(qū)上三疊統(tǒng)延長組差異較大;爭議地層砂巖樣品中含13顆中生代年輕碎屑鋯石((188±3)~(254±8)Ma)(占總數(shù)17%),其中3顆碎屑鋯石U-Pb年齡小于200 Ma,最年輕的碎屑鋯石年齡限制了爭議地層最大沉積年齡小于(188±3)Ma。爭議地層中發(fā)育的晚三疊世孢粉組合,是三疊系孢粉化石再旋回的結(jié)果,鄂爾多斯盆地西南緣強(qiáng)烈的印支運(yùn)動導(dǎo)致三疊系很快抬升至地表遭受剝蝕,為近區(qū)早—中侏羅世地層提供物源,古生物化石亦隨之混入近區(qū)沉積地層中。根據(jù)上述證據(jù)和討論,將六盤山地區(qū)中生代煤系地層時代重新歸為早—中侏羅世,這一結(jié)論具有重要科學(xué)研究和油氣勘探價值。
[Abstract]:In order to correctly divide the Mesozoic coal measures strata in the Liupanshan area with "Upper Triassic or Lower Middle Jurassic" dispute, the field sedimentary phenomena were observed. The mineralogical study under microscope and LA-ICP-MS U-Pb isotopic dating of sandstone zircon have redefined the age of the coal-bearing strata. Iron nodules are commonly developed in the disputed strata in Liupanshan area. The sandstone differential weathering is serious, which is similar to the lower and middle Jurassic Yan'an formation in the adjacent area, but is quite different from the Yanchang formation of the Upper Triassic in the adjacent area. The sandstone samples of the disputed strata contain 13 young Mesozoic detrital zircons (188 鹵3) and 254 鹵8 Majiao (17 in total). The U-Pb age of three detrital zircons is less than 200 Ma. The youngest clastic zircon age limits the maximum sedimentary age of the disputed strata to less than 188 鹵3 Ma. The late Triassic sporopollen assemblage developed in the disputed strata is the result of the recycle of the Triassic sporopollen fossils. The strong Indosinian movement in the southwest margin of the Ordos Basin caused the Triassic to rise to the surface of the earth to be eroded quickly, which provided a material source for the early and Middle Jurassic strata in the near area. According to the above evidence and discussion, the Mesozoic coal-bearing strata in Liupanshan area were reclassified to early and middle Jurassic. This conclusion has important scientific research and oil and gas exploration value.
【作者單位】： 西北大學(xué)大陸動力學(xué)國家重點(diǎn)實(shí)驗(yàn)室西北大學(xué)地質(zhì)學(xué)系;
【基金】：國家自然科學(xué)重點(diǎn)基金項(xiàng)目(41330315) 中國地質(zhì)調(diào)查局項(xiàng)目(12120113039900,12120114009201)
【分類號】：P597.3;P618.11
【正文快照】： GUO Pei,LIU Chiyang*,WANG Jianqiang,DENG Yu,ZHAO Xiaochen,WANG Wenqing,WANG LeiState Key Laboratory of Continental Dynamics;Department of Geology,Northwest University,Xi，

本文編號：1480094