Research On Organic-walled Microfossils Of The Shiwangzhuang Formation,Anqiu,Shandong And The Chuanlinggou Formation,Jixian,Tianjin

Palaeontology of the Proterozoic is very significant for understanding the origin and evolution of early life,carrying out biostratigraphic correlation,restoring palaeoenvironment,etc.Thus,research on the Proterozoic fossils is always in hotspot.Proterozoic strata is well exposed within western Shandong and Jixian,Tianjin with abundant fossil resources.By launching geological investigation in both areas respectively,we conducted research on the organic-walled microfossils of the Neoproterozoic Shiwangzhuang Formation in western Shandong and the Mesoproterozoic Chuanlinggou Formation in Jixian,Tianjin.Fossil records have never been reported from the Shiwangzhuang Formation before,except for those in stromatolite.Acid maceration technique was applied to preparation for extracting organic-walled microfossils,and then a number of specimens were revealed,which fills in gap in microfossils.The organic-walled microfossil assemblage of the Shiwangzhuang Formation consists mainly of smooth-walled sphaeromorphic acritarchs and probable cyanobacteria filaments,as well as low abundance of other acritarchs.A total of 18 taxa belonging to 11 genera has been identified,including Leiosphaeridia minutissima,L.tenuissima,L.jacutica,L.crassa,Ostiana microcystis,Simia annulare,Siphonophycus typicum,S.kestron,S.punctatum,S.solidum,Synsphaeridium sp.,?Jacutianema sp.,Arctacellularia tetragonala,Polysphaeroides filliformis,Pellicularia tenera,Polytrichoides lineatus,Navifusa actinomorpha and Navifusa majensis.This result not only fills in gap in micropalaeontological data of the Shiwangzhuang Formation but also lays foundation for strata correlation.Combined with previous works in palaeontology and isotope chronology,the depositional age of the Shiwangzhuang Formation is discussed further.We systematically collected shale samples of the Chuanlinggou Formation at the Jixian section and then revealed numerous organic-walled microfossils using the method mentioned above.Characterised by smooth-walled sphaeromorphic acritarchs and low diversity,the microfossils from the Chuanlinggou Formation have been identified as 4 taxa including Leiosphaeridia spp.,Schizofusa sinica,Valeria lophostriata and?Simia annulare.The preservation of microfossils is affected by many paleoenvironmental factors.Abundant microfossil materials in this research are provided for further research on biological affinity.