Cyanobacterial fossils from 252 Ma old microbialites and their environmental significance.
The end-Permian mass extinction was followed by the formation of an enigmatic rock layer with a distinctive macroscopic spotted or dendroid fabric. This deposit has been interpreted as microbial reef rock, digitate dendrolite, digital thrombolite, dendritic thrombolite, or bacterial deposits. Agreement has been reached in considering them as microbialites, but not in their formation. This study has revealed that the spotted and dendroid microbialites were composed of numerous fossil casts formed by the planktic cyanobacterium, Microcystis, a coccoid genus that at the present-day commonly forms blooms in modern lakes, rivers, and reservoirs. The abundance of the fossils and the diagenesis they experienced has determined the macroscopic fabric: where they abundant, the rock appears as dendroid, otherwise, it appears as spotted. The ancient Microcystis bloom might produce toxin to kill other metazoans, and be responsible for the oceanic anoxia that has puzzled so many researchers for so many years.
Institute of Geology and Geophysics, Chinese Academy of Sciences, Key Laboratory of Petroleum Resource Research, CAS, Beijing 100029, People's Republic of China.
Ya Sheng
YS
Wu
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
Gong Liang
GL
Yu
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
Ren Hui
RH
Li
Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430071, People's Republic of China.
Li Rong
LR
Song
Institute of Geology and Geophysics, Chinese Academy of Sciences, Key Laboratory of Petroleum Resource Research, CAS, Beijing 100029, People's Republic of China.
Hong Xia
HX
Jiang
Department of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN 37996, USA.
Robert
R
Riding
Institute of Geology and Geophysics, Chinese Academy of Sciences, Key Laboratory of Petroleum Resource Research, CAS, Beijing 100029, People's Republic of China.
Li Jing
LJ
Liu
Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, Yantai 264003, People's Republic of China.
Dong Yan
DY
Liu
Institute of Geology and Geophysics, Chinese Academy of Sciences, Key Laboratory of Petroleum Resource Research, CAS, Beijing 100029, People's Republic of China.
Rui
R
Zhao
D000458:Cyanobacteria / Q000254:growth & development*; D004783:Environmental Microbiology; D053476:Extinction, Biological; D005580:Fossils; D060106:Lakes / Q000737:chemistry* / Q000382:microbiology; D045483:Rivers / Q000737:chemistry* / Q000382:microbiology