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What is a Reef ?

Coral Reef Geology. What is a Reef ?. Wilson Ramirez. Perspective….what is a reef?. Mariners Can I hit my keel on it (i.e., shallow) Biologists Biologically abundant and diverse assemblage Geologists Biologically built Wave resistant Stands above its surroundings.

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What is a Reef ?

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  1. Coral Reef Geology What is a Reef ? Wilson Ramirez

  2. Perspective….what is a reef? • Mariners • Can I hit my keel on it (i.e., shallow) • Biologists • Biologically abundant and diverse assemblage • Geologists • Biologically built • Wave resistant • Stands above its surroundings

  3. Perspective….what is a reef? Canning Basin, Australia (Devonian) • Mariners • Can I hit my keel on it (i.e., shallow) • Biologists • Biologically abundant and diverse assemblage • Geologists • Biologically built • Wave resistant • Stands above its surroundings Palau, Oceania

  4. Canning Basin, Australia (Devonian) Isla de Mona, Puerto Rico

  5. A Geologist’s Reef

  6. Reef Definition “the vast majority of of ancient reef deposits are comprised not of in-place, interlocking framework, but rather are loose assemblages with reef-building organisms ‘floating’ in a matrix of reef-derived debris” Hubbard (1997, p. 43)

  7. Reef Definition Stanley (2001) “Growth of biological framework on modern shallow reefs is rapid….” “…it is counterbalanced by highly destructive (recycling) processes…”

  8. “Reef” definition • Constructed of material of biological origin • Rigid structure, owing to either interlocked and in place framework elements or of re­worked framework elements bound together by secondary encrustation or cementation • Stands topographically above the surrounding seascape and, therefore, exerts at least local control on oceanographic processes • The majority of the framework elements were formed in an environment similar to the one in which they were ultimately deposited

  9. Tucker & Wright

  10. A Geologic Reef • Rigid, & wave resistant • Elevated - affect local oceanography • Near sea level?

  11. Let’s put this into a geological perspective… The reef is "apparent" i.e., no topography actually occurred in the past

  12. Stratigraphic reef An oyster bank is not wave resistant, but in time a thick sequence could result from upward layered accumulation.

  13. Topography at the time of deposition

  14. Ecologic reef accumulation Fossil reef with in place structural elements – Acropora palmata

  15. Question: What differences will we see at A versus B? A B BIOHERM BIOHERM

  16. e.g., a coral”carpet” No significant topography Question: What differences will we see at A versus B? A B BIOSTROME

  17. Biostrome vs. Bioherm Relief During No Original Relief Deposition

  18. How do we get rigid, elevated structures? • Construction • Corals • Other calcifiers • Destruction • Fish • Urchins • Borers • Encrustation • Cementation Coral Growth

  19. Corals Grow Reefs Accrete (or build) Sediment production and redistribution

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