A new Palaeoproterozoic clastic-facies microbiota from the Changzhougou Formation, Changcheng Group, Jixian, north China

Abundant microfossils have recently been discovered in the late Palaeoproterozoic Changzhougou Formation, Changcheng Group, Jixian, north China. The Changzhougou microbiota consists dominantly of sphaeromorph acritarchs and some osillatoriacean cynobacterial filaments. The microfossils were recovered from shales and are compressed on bedding surfaces. The sphaeromorph acritarchs, ranging from 8.4 to 237.8 mu m in diameter, are morphologically simple. On the basis of their dimensions and morphological considerations, the sphaeromorph acritarchs are interpreted as probably representing the resistant, reproductive cysts of unicellular protists. This assemblage is evidently among the oldest known clastic-facies microbiotas in the geological record and provides evidence of protist eukaryotes being extant at 1848 Ma.