1

The History of Early Mesozoic Reef Communities: A Three-

Step Process

The History of Early Mesozoic Reef Communities: A Three-

Step Process

Stanely Jr., George D

Palaios (1988) 3:170-183

Stanely Jr., George D

Palaios (1988) 3:170-183

Evolution of Modern Reef CommunitiesEvolution of Modern Reef Communities

Permian Reef CommunitiesPermian Reef Communities

• Sponges• Byzoans• Tubiphytes• Algae• Tabulate Corals• Rugose “Horn” Corals

• Sponges• Byzoans• Tubiphytes• Algae• Tabulate Corals• Rugose “Horn” Corals

Permian-Triassic ExtinctionPermian-Triassic Extinction

Permian HoldoversPermian Holdovers Permian HoldoversPermian Holdovers

2

Middle Triassic Reef CommunitiesMiddle Triassic Reef Communities• Identical to Permian Reefs

• Scleractinian Corals– Competitively weak– Asymbiotic

• Identical to Permian Reefs

• Scleractinian Corals– Competitively weak– Asymbiotic

Karnian-Norian ExtinctionKarnian-Norian Extinction

Symbiosis

Triassic-Jurassic ExtinctionTriassic-Jurassic Extinction Triassic-Jurassic ExtinctionTriassic-Jurassic Extinction

• Loss of competitive species enabled coral dominance

• Quick adaptive radiation of corals (21-100 genera)

• Leads to modern reefs

• Loss of competitive species enabled coral dominance

• Quick adaptive radiation of corals (21-100 genera)

• Leads to modern reefs

ConclusionsConclusions

• Middle-Triassic and Permian reefs near identical (unique among mass extinctions)

• Minor extinction event/evolution of symbiosis led to dominance of Scleractinia

• Major extinction event followed by rapid coral diversification and reef building

• Extinctions important in structuring biological communities

• Middle-Triassic and Permian reefs near identical (unique among mass extinctions)

• Minor extinction event/evolution of symbiosis led to dominance of Scleractinia

• Major extinction event followed by rapid coral diversification and reef building

• Extinctions important in structuring biological communities

Paleoceanography of the coral reefs in the Hawaiian-Emporer

Chain- revisited

Paleoceanography of the coral reefs in the Hawaiian-Emporer

Chain- revisited

Grigg, R. W.

Coral Reefs (1997) 16:S33-S38

Grigg, R. W.

Coral Reefs (1997) 16:S33-S38

3

Evolution of Hawaii-Emperor chainEvolution of Hawaii-Emperor chain Elevation and ageElevation and age

Atoll FormationAtoll Formation Fringe reefsFringe reefs

• Youngest fringe reefs on 100 year old volcanic foundations on Hawaii

• Can form in 100-1000 years

• Youngest fringe reefs on 100 year old volcanic foundations on Hawaii

• Can form in 100-1000 years

Barrier ReefsBarrier Reefs

• Found on outer part of Oahu (2.5Ma)• Found on outer part of Oahu (2.5Ma)

AtollsAtolls

• French Frigate Shoals (11.7 Ma)• French Frigate Shoals (11.7 Ma)

4

Coral growth and latitudeCoral growth and latitude BiogeographyBiogeography

• Oldest colony ~35Ma• Oldest Seamount ~70Ma

– Biogeographic barriers prevented Hawaiian chain colonization

• Oldest colony ~35Ma• Oldest Seamount ~70Ma

– Biogeographic barriers prevented Hawaiian chain colonization

ConclusionConclusion

• Hawaiian-Emperor chain is an excellent model for paleoceanography studies

• Coral reefs can only survive as long as accreation > bioerosion/subsidence/transgression

• Lifespan of 28 million years

• Hawaiian-Emperor chain is an excellent model for paleoceanography studies

• Coral reefs can only survive as long as accreation > bioerosion/subsidence/transgression

• Lifespan of 28 million years