Understanding the origin of ancient carbonate ooids: recent findings

ABSTRACT

The origin and micro-texture of ooids remain controversial. This study presents a review of microstructure of ooids and explains the origin of microstructures in Cambrian ooids in the North China Platform. Factors controlling the morphology and mineral composition of ooid are very complex. Ooids form by a combination of physical, chemical and biological processes, in various environments. Recent studies on modern Bahamian ooids and laboratory experiments with microbial cultures highlight the formation of ooids without detailed explanation of the role of amorphous calcium carbonate (ACC). This review reinforces the biochemical hypothesis for the origin of ooids and proposes the sequence of microbial activities that involves the active and stationary stages in its formation. Microbes, particularly the filamentous fossils of calcified sheath of cyanobacteria, excrete extracellular polymeric substances (EPS) that act as a template for the formation of ACC. The dark micrite bands, dominated by filamentous cyanobacteria within the cortex and the core of the Cambrian pelagic and benthic ooids of the North China Platform supports the biochemical origin of ooid formation.

KEYWORDS:

• Filamentous cyanobacteria
• Extracellular polymeric substance
• Amorphous calcium carbonate
• Carbonate precipitation
• Ooid

Acknowledgments

We gratefully acknowledge Mei Mingxiang (CUGB), who provided us guidance and financial support from the National Natural Science Foundation of China (Grant No. 41472090, 40472065) for this fieldwork. This research was also funded by Researchers Supporting Project number (RSP2023R455), King Saud University, Riyadh, Saudi Arabia. We gratefully acknowledge the Dr. Lowell Waite (University of Texas at Dallas) and an anonymous reviewer for constructive comments, which have greatly improved the quality of the paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2220390

Additional information

Funding

This research was funded by the National Natural Science Foundation of China (grant 41472090). This research was also funded by Researchers Supporting Project number (RSP2023R455), King Saud University, Riyadh, Saudi Arabia.