摘要:
在豫西北奥陶系马家沟组碳酸盐岩中共识别出三大生态类型的遗迹化石10属17种:①居住迹(Domichnia):Psilonichnus upsilon、Thalassinoides callianassa、Thalassinoides horizontalis、Rhizocorallium jenense;②进食迹(Foidichnia):Chondrites type-1、Chondrites type-2、Chondrites intricatus、Palaeophycus tubularis、Palaeophycus heberti、Planolites montanus、Planolites annularius、Phycodes palmatus;③觅食迹(Pascichnia):Helminthopsis ichnosp.、Helminthopsis abeli、Helminthopsis hieroglyphica、Gordia molassica、Scolicia ichnosp.按其古生态和沉积学特征,可划分出三个遗迹组合:①Psilonichnus-Thalassinoides 遗迹组合,代表局限碳酸盐岩台地内的潮坪环境;②Helminthopsis-Gordia遗迹组合,反映局限碳酸盐岩台地的潟湖或开阔碳酸盐岩台地内的滩间海和台内洼地等低能、静水的沉积环境;③Chondrites-Scolica遗迹组合,指示开阔碳酸盐岩台地内洼地中氧化还原界面附近的沉积环境。综合岩石类型、岩石序列组合、沉积构造、生物化石、遗迹化石或遗迹化石组合,建立了研究区奥陶系马家沟组的沉积模式和垂向沉积演化序列。
Abstract:
Trace fossils from Ordovician Majiagou Formation consist of at least 10 ichnogenera and 17 ichnospecies, namely, (1)Domichnia: Psilonichnus upsilon, Thalassinoides callianassa, Thalassinoides horizontalis, Rhizocorallium jenense.(2)Foidichnia: Chondrites type-1, Chondrites type-2, Chondrites intricatus, Palaeophycus tubularis, Palaeophycus heberti, Planolites montanus, Planolites annularius, Phycodes palmatus.(3)Pascichnia: Helminthopsis ichnosp., Helminthopsis abeli, Helminthopsis hieroglyphica, Gordia molassica, Scolicia ichnosp. According to their palaeoecological and sedimentological features, these trace fossils can be divided into 3 ichnoassemblags, ie,①Psilonichnus-Thalassinoides ichnoassemblage, forming in tidal sedimentary environment of Restricted carbonate platform, mainly composed of Psilonichnus ,Thalassinoides, Helminthopsis. ②Helminthopsis-Gordia ichnoassemblage, which is associated with lagoon sedimentary environment of restricted carbonate platform, interbank sea or depression of open carbonate rock platform, mainly composed of Helminthopsis, Gordia, planolites, Palaeophycus, Thalassinoides. ③Chondrites-Scolica ichnoassemblage, which indicates the depression of open carbonate rock platform near the REDOX interface. Finally, depositional model of the Ordovician Majiagou Group and the vertical sedimentary evolution sequence was established based on integrated rock types, rock sequence, sedimentary structure, fossils with trace fossils or ichnoassemblage.