中国中—新生代陆相沉积中的遗迹群落

The Ichnocoenoses of Mesozoic-Cenozoic Terrestrial Deposits of China

中国中新生代陆相沉积地层中的遗迹化石已知七大生态类型近 4 0种 ,按其形成的沉积环境可大致划分为三大遗迹群落 ,即①Scoyenia遗迹群落 ,代表冲积平原或三角洲平原至滨湖环境 ;②Macaronichnus Planolites遗迹群落 ,主要产生于浅湖环境及水下砂扇 (扇三角洲、浊积扇 )沉积环境 ;③Mermoides Neonereites遗迹群落 。

The seven ethological types (about 40 ichnospecies) of trace fossils in Mesozoic-Cenozoic terrestrial deposits of China were briefly summarized. According to their palaeoecological and sedimentological features , these trace fossils can be divided into 3 larger ichnocoenoses, i.e. (1) Scoyenia ichnocoenosis, occurring in the alluvial plain or delta plain and shore deposits including extremely shallow lacustrine deposits, which is characterized by the fully abundant Scoyenia ichnogenus, and commonly associated with Steinichnus, Beaconites, Taenidium, Cystichnium, Palaeophycus, Gordia, Planolites, Paradidymaulichnus, Monomorphichnus, Cf.Oniscoidichnus, Rusophycus, Pelecypodichnus, Arenicolites, Skolithos, Margaritichnus, Macaronichnus, Planolites and Rhizoliths and so on . These tracefossils may be further divided into 4 assemblages including Scoyenia-Steinichnus-Rusophycus assemblage formed in the regularly desiccated flood plain and overbank origin, Scoyenia-Beaconites-Palaeophycus assemblage resulted from the regularly desiccated muddy and sandy shore or extremely shallow lacustrine deposits in the delta plain, Skolithos-Arenicolites assemblage associated with the point bar, deltaic distributary channel bar, distributary mouth bar and sandy shore deposit environments, and Macaronichnus -Rhizoliths assemblage related to the depression deposit settings between delta plain distributary channel; (2) Macaronichnus-Planlites ichnocoenosis, forming in the shallow lacustrine deposits including lower delta fan and turbidity fan deposits or flood deposits (inundates), which mainly consists of a set of Macaronichnus, Planolites (varied size of types) , Monocraterion, Skolithos, Arenicolites, Gordia, Palaeophycus, Cochlichnus, Helminthoidichnites,Helminthopsis and Brevitubus and so on, they may be also divided into 2 assemblages containing Macaronichnus-Monocraterion assemblage and Macaronichnus Helminthopsis assemblage, the former occurs in the delta front sheet bar, sand fan or turbidite fan (middle outer fan) deposit setting and the latter is related to the shallow lacustrine deposits ; (3) Mermoides-Neonereites ichnocoenosis, it is the typical represent of the deeper lacustrine deposits, which is predominantly composed of Mermoides (a new ichnogenus, similar to Mermia discussed by Buatois and Mangano, 1995), Neonereites, Gordia,Vagorichnus, Helminthoidichnites,Planolites, Cochlichnus, Helminthopsis, Monomorphichnus, Paracanthorhaphe, Tuberculichnus and so forth. In summary, just as figure 1, above 3 larger ichnocoenoses and 6 ichno assemblages generally display the total composition characteristics of trace fossils from alluvial plain (flood plain) or delta plain through shore and shallow lacustrine to deeper lacustrine deposit environments.