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Succession in Reefs• 4 stages :
1. Pioneering or Stabilization
a. Accumulation of skeletal debris
b. Creation of a surface with some relief
Succession in Reefs
3. Diversification
a. Increased diversity of organisms
b. Takes the form of a massive structure
Succession in Reefs
4. Domination
a. “lamellar framestones”
b. Evidence of high water energy (rudstones)
c. Species diversity is reduced
Reef Evolution
Archaeocyathids (sponges?)
Lowly Pond Scum
Cambrian 500 my
12 bybp
Precambrian570 my
www.netrocks.netinyo.topcities.com
Stromatolites
Reef Evolution
12 bybp
Loss of “ecospace”
What happens witha sea-level fall?
Precambrian570 my
Back to “pond slime”
Devonian
Stromatoporoids;Rugose Corals Crinoids
StromatolitesCambrian
Ordovician500 my
430 myStromatoporoids (sponges?)
Silurian
12 bybp
390 myStromatoporoids;Tabulate Corals Crinoids
Devonian
280 myPermian
Sponges
Devonian
360 myCarboniferous
A time of poor reef development Major coal swamps
Reefs made of sponges…..
The Capitan Reef Complex
Just when things were looking good…..
Sea-Level DropsSea Level Back Up
280 myPermian
Sponges
Reefs disappear!!!!!!!!245 my
Triassic
Extinction
• Sea level - no• Climate change - maybe• Ocean chemistry?
Why?
Scleractinean corals
280 myPermian
Sponges
245 myTriassic
A watershed event in reef history??
20 million yr gap
Cretaceous
Rudists
• The cup shaped form is back…..• but it’s a mollusk this time???
Triassic --> Jurassic
Scleractineans
140 my
A broadening tropics
An open pan-equatorial seaway
Why mollusks and not corals???
• High temperatures
• “Greenhouse” climate much warmer than today
• Too warm for corals
Rudist Reefs
Photo by D. Schumann (from Woods, 1999)
Drawing by John Sibbick (in Woods, 1999)
They photosynthesized??the missing article……
Cretaceous Time
Images by Mary Parrish, NMNH
The End of theCretaceous
Irridium
ExtinctionDewey McLean
Return tosclractinean
corals
Reefs have stayed pretty much the same ever since
65 myTertiary
Rest of the Cenozoic