Research Letter 

Biopetrology, 1(2): 61-69.  18 November, 2022

Earth's oldest stromatolites in the 3.7 billion years old rocks from Greenland: evidence of benthic microbial communities 

Ya-Sheng Wu^1,2,3    Hong-Xia Jiang⁴

¹Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China.

²Innovation Academy for Earth Science, Chinese Academy of Sciences, Beijing 100029, China.

³University of Chinese Academy of Sciences, Beijing 100049, China.

⁴Hebei Key Laboratory of Strategic Critical Mineral Resources, Institute of Paleontology, Hebei GEO University, Shijiazhuang 050031, China. 

^*Corresponding author: jianghx@hgu.edu.cn, wys@mail.igcas.ac.cn.

Abstract

Stromatolites and laminite are record of benthic microbial communities. Here we report two stromatolites and one laminite we recognized from the published photos of the 3.7-billion-year old rocks in Isua, Greenland, which were used as the examples of structural folds in abiogenic laminated structures by previous researchers to argue against the interpretation of some conic structures as the earliest stromatolites by the earlier researchers. In order to help distinguish stromatolites from tectonic folds and laminites from abiogenic laminated rocks, here we propose three criteria for identifying stromatolites: (1) columnar, dome-like, and conic forms, (2) their axis are not in a convergent arrangement, and (3) their laminae are in dome-like or conic form, irregularly sinuous, often furcate, and merge in their lateral surface. According to these criteria, we reached the conclusion that the conic structures reported by the previous researchers are not stromatolites. Our recognition of these earliest microbialite rocks shows that the benthic microbial communities were present 3.7 billion years ago. 

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