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Coral microatolls and a probable Middle Ordovician example

Published online by Cambridge University Press:  20 May 2016

David R. Kobluk  and
Iqbal Noor
David R. Kobluk
Affiliation:
Department of Geological Sciences, J. Tuzo Wilson Research Laboratories, Erindale Campus, University of Toronto, Mississauga, Ontario L5L 1C6, Canada
Iqbal Noor
Affiliation:
Department of Geological Sciences, J. Tuzo Wilson Research Laboratories, Erindale Campus, University of Toronto, Mississauga, Ontario L5L 1C6, Canada
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Abstract

A disk-shaped massive colony of Tetradium, from the Middle Ordovician Bobcaygeon Formation in southern Ontario, displays features of a coral microatoll. This is the first pre-Holocene coral microatoll yet described, indicating that some tabulate corals in level-bottom communities were growing as microatolls as do many modern colonial skeleton-secreting organisms.

The microatoll therefore is not strictly a Quaternary or even Cenozoic phenomenon, but has a fossil record that may span most of the Phanerozoic. This indicates that the special conditions necessary for microatoll growth have existed outside of reef environments, and were present before the advent of scleractinian coral reefs. It may be possible to use ancient microatolls to estimate absolute water depths at low tide, thereby providing a means for estimating maximum water depths on a local and regional scale.

Type
Research Article
Information
Journal of Paleontology , Volume 64 , Issue 1 , January 1990 , pp. 39 - 43
Copyright
Copyright © The Paleontological Society 

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