Himalayan Geology, Vol. 41 (2), 2020, pp. 183-194, Printed in India
The genetic implications of microbial fossils for microbial carbonate: An example of Cambrian in North China Platform
ENZHAO XIAO1, KHALID LATIF1,2, MUHAMMAD RIAZ3,4,5*
1School of Earth Sciences and Resources, China University of Geosciences, Beijing,100083, China
2National Centre of Excellence in Geology, University of Peshawar, Peshawar, 25130, Pakistan
3State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, 610059, China
4College of Energy Resources, Chengdu University of Technology, Chengdu, 610059, China
5Institute of Geology, University of the Punjab, Lahore, 54590, Pakistan
*Email (Corresponding author): riazjass@yahoo.com
Abstract: The Cambrian Changshan Formation at the Qijiayu section constitutes the lower part of the Furongian Series. The formation is characterized by a shallowing upward succession of sedimentary facies ranging from mudstone of shelf facies to micrite of shallow ramp facies and therefore, constituting a third-order carbonate depositional sequence of the drowning unconformity type in the north of the Taihang Mountain in Laiyuan City of Hebei Province. A single bed of the micrite comprising of shallow ramp facies in the upper part of the Changshan Formation contains many dome-shaped carbonate structures with distribution like a string of beads. These structures can be described as leiolitic bioherm, which represents the evidence of a forced regression. Various calcified microorganisms such as Epiphyton, Girvanella and Renalcis developed within the leiolitic bioherm, which not only provide documentation for the first episode of “cyanobacteria calcification event” in the Phanerozoic, but also describe the leiolitic bioherm formed from the microbial mats that are dominated by cyanobacteria. Furthermore, the partial concentrations of benthic ooids and framboidal pyrite in the leiolitic bioherm show the complex microbial sedimentation during the formation of the bioherm. Although, the micrite and microspar are the basic components of the bioherm, growth of the calcified microorganisms, benthic ooids and framboidal pyrite in leiolitic bioherm offers a reference for studying the complex microbial activity signals in the microbial mats dominated by calcified microorganisms. It can also be regarded as an instance for further research on the mechanism of microbial carbonate formation.
Keywords: Epiphyton, Girvanella, Renalcis, Benthic ooids, Furongian Epoch.
