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Early Ordovician shift in reef construction from microbial to metazoan reefs

Natsuko Adachi, Yoichi Ezaki and Jianbo Liu
Early Ordovician shift in reef construction from microbial to metazoan reefs
Palaios (February 2011) 26 (2): 106-114

Abstract

The Ordovician is a period when novel reef ecosystems appeared along with new reef constructors and skeletal-dominated reefs. The Lower Ordovician (late Tremadocian) Fenhsiang Formation of the Three Gorges area in South China contains the oldest known bryozoan reefs (lithistid sponge-bryozoan and bryozoan-pelmatozoan reefs) alongside lithistid sponge-microbial reefs. The latter are characterized by the dominance of microbialites that encrusted and bound the frame-building sponges and inter-sponge sediments. In contrast, the lithistid sponge-bryozoan and bryozoan-pelmatozoan reefs are generally characterized by bryozoans that encrusted the frame-building sponges or pelmatozoans and grew to fill the inter-frameworks. These sponges and pelmatozoans did not construct the rigid frameworks unaided; their association with bryozoans enabled the development of small skeletal-dominated reefs with rigid frameworks. Skeletal-dominated reefs, for which frame-constructing and encrusting roles are conspicuous, were largely unknown before the Early Ordovician. The appearance of skeletal organisms (specifically colonial, encrusting bryozoans) enabled the development of skeletal-dominated reefs, which were pioneers in the rise of Middle-Late Ordovician reefs. The Early Ordovician establishment of skeletal-dominated reefs at the earliest stages of the Great Ordovician Biodiversification Event would have created novel niches and biological interactions that further promoted the evolution of reef-building and -dwelling organisms, as well as ensuing reef ecosystems.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 26
Serial Issue: 2
Title: Early Ordovician shift in reef construction from microbial to metazoan reefs
Affiliation: Peking University, School of Earth and Space Sciences, Beijing, China
Pages: 106-114
Published: 201102
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 60
Accession Number: 2011-019944
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. col., 1 table, sketch map
N30°52'60" - N30°52'60", E111°22'60" - E111°22'60"
Secondary Affiliation: Osaka City University, JPN, Japan
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 201112
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