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引用本文:荆锡贵,李凤杰,成晓雨,杨晓琪,张昊,沈凡. 四川龙门山地区早-中泥盆世混积相遗迹化石及其环境分析[J]. 中国地质, 2018, 45(2): 377-391.
JING Xigui,LI Fengjie,CHENG Xiaoyu,YANG Xiaoqi,ZHANG Hao,SHEN Fan. Trace fossils of hybrid facies from Early-Middle Devonian strata in Longmenshan area, Sichuan Province[J]. Geology in China, 2018, 45(2): 377-391(in Chinese with English abstract).
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四川龙门山地区早-中泥盆世混积相遗迹化石及其环境分析
荆锡贵1, 李凤杰1, 成晓雨1, 杨晓琪2, 张昊1, 沈凡1
1.成都理工大学沉积地质研究院, 四川 成都 610059;2.新疆煤制天然气外输管道有限责任公司, 北京 100728
摘要:
龙门山地区早-中泥盆世碳酸盐岩和碎屑岩组成的混合沉积相富含大量海相遗迹化石,可识别居住迹、进食迹、觅食迹、爬行迹和停息迹5大类14属,包括居住迹:Skolithos;进食迹:Chondrites、Phycodes、Planolites、Rhizocorallium、ThalassinoidesZoophycos;觅食迹:Cylindrichnus以及Palaeophycus;爬行迹:CruzianaMonomorphichnus;停息迹:Asterichnus、LockeiaRusophycus等,这些遗迹化石分属于4个遗迹化石组合,反映了不同沉积环境,分别为:(1)Skolithos-Thalassinoides遗迹组合,沉积于高能砂质环境中,为水动力较强的无障壁滨岸前滨;(2)Rusophycus-Phycodes遗迹化石组合反映了水动力较弱的近滨环境;(3)Chondrites-Palaeophycus遗迹化石组合反映了贫氧、水动力条件较弱的近滨下部环境;(4)Zoophycos-Palaeophycus遗迹化石组合反映的环境为正常浪基面以下,风暴浪基面以上的风暴沉积环境,据此建立了龙门山地区早-中泥盆世混积相遗迹化石生活环境分布模式。龙门山地区早-中泥盆世发现的3种类型Zoophycos遗迹化石,与腕足介壳富集层、波痕、丘状和洼状交错层理等反映浅水环境的沉积特征共存,表明泥盆纪Zoophycos形成于浅水环境。
关键词:  遗迹化石  古环境  混积相  泥盆纪  龙门山地区
DOI:10.12029/gc20180212
分类号:P534.44;Q911.28
基金项目:国家自然科学基金项目“龙门山地区泥盆纪土桥子组高频韵律旋回成因及古气候意义研究”(41172100)和四川省教育厅自然科学重点项目“龙门山地区泥盆纪风暴沉积及其地质意义”(12ZA012)联合资助。
Trace fossils of hybrid facies from Early-Middle Devonian strata in Longmenshan area, Sichuan Province
JING Xigui1, LI Fengjie1, CHENG Xiaoyu1, YANG Xiaoqi2, ZHANG Hao1, SHEN Fan1
1.Institute of Sedimentary Geology, Chengdu University of Technology, Chengdu 610059, Sichuan, China;2.SINOPEC Xinjiang Coal Natural Gas Transmission Pipeline Co., Ltd., Beijing, 100728, China
Abstract:
Abundant marine trace fossils are preserved in the Early-Middle Devonian strata of the Guixi-Shawozi section in Longmenshan area, Sichuan Province. According to the shapes, three types of trace fossils were identified that include Domichnia as Skolithos, Fodinichnia as Chondrites, Phycodes, Planolites, Rhizocorallium, Thalassinoides and Zoophycos; Food-seeking traces including Cylindrichnus and Palaeophycus; Repichnia as Cruziana and Monomorphichnus; Cubichnia as Asterichnus, Lockeia and Rusophycus. 14 kinds in total trace fossils can be identified clearly. The ichnocoenoses represent types of Domichnia, Fodinichnia, Food-seeking traces, Repichnia and Cubichnia. Four ichnocoenoses representing different sedimentary environments were recognized as follows:(1) Skolithos-Thalassinoides ichnocoenosis can be explained as Domichnia from higher-energy foreshore; (2) Rusophycus-Phycodes ichnocoenosis mainly consists of Cubichnia and Fodichnia generated in higher-energy nearshore; (3) Chondrites-Palaeophycus ichnocoenosis is from shallow shelf, which suggests sub-oxic and lower energy; (4) ZoophycosPalaeophycus ichnocoenosis is considered as Fodichnia from higher-energy shallow shelf between normal wave base to storm wave base. In terms of the ichnocoenoses, living environment and distribution pattern of trace fossils of hybrid facies were set up from Early-Middle Devonian strata in Longmen-shan area. Three kinds of Zoophycos fossils were observed, which were coexistent with concentrations of brachiopoda and shell, ripple marks, hummocky and swaley cross bedding, which reflects shallow environment sedimentary characteristics from Early to Middle Devonian in Longmenshan area and indicates that Zoophycos fossils were formed in a shallow environment.
Key words:  trace fossil  paleoenvironment  hybrid facies  Devonian  Longmenshan area