Doushantuo-type microfossils from latest Ediacaran phosphorites of northern Mongolia
Doushantuo-type microfossils from latest Ediacaran phosphorites of northern Mongolia
Geology (Boulder) (December 2017) 45 (12): 1079-1082
- acritarchs
- Asia
- assemblages
- biostratigraphy
- C-13/C-12
- carbon
- chemically precipitated rocks
- Ediacaran
- Far East
- fossilization
- ichnofossils
- isotope ratios
- isotopes
- microfossils
- Mongolia
- Neoproterozoic
- palynomorphs
- phosphate rocks
- Precambrian
- preservation
- Proterozoic
- sedimentary rocks
- stable isotopes
- upper Precambrian
- northern Mongolia
- Megasphaera
- Khesen Formation
- Khuvsgul Group
- Doushantuo-type microfossils
Phosphorites of the latest Ediacaran upper Khesen Formation in the Khuvsgul Group of northern Mongolia preserve a newly discovered, three-dimensionally phosphatized Doushantuo-type microfossil assemblage. Eight genera include the second occurrence of the putative multicellular fossil animal embryo Megasphaera outside South China, the Doushantuo-Pertatataka-type acanthomorphic acritarchs h Cavaspina, and Variomargosphaeridium, and the possible alga Archaeophycus yunnanensis. The assemblage occurs in the lowermost phosphorite horizon in foreland basin deposits on the Khuvsgul terrane; lithostratigraphic and delta (super 13) C correlation with the Zavkhan terrane of southwestern Mongolia establishes a latest Ediacaran age for the fossiliferous phosphorites. Thus, this is the youngest Doushantuo-type assemblage yet reported. It extends the range of Megasphaera, and fills a gap in the record of phosphatized embryo-like forms between the ca. 600 Ma Doushantuo Weng'an biota and Cambrian examples. The Khesen fossil assemblage emphasizes the potential of Mongolian phosphorites to provide new paleontological data on the Ediacaran-Cambrian transition, and to resolve the phylogenetic debate surrounding Megasphaera embryo-like taxa.