reef definition

[Markus Bertling]

Dear all,
as a member of two groups grossly underrepresented on this list (Germans
and geologists) I have to second Mike Risk:
- "corals" have nothing to do in a reef definition: One of the most famous
reefs of ALL times, the Capitan reef in TX and adjacent states, completely
lacks corals! It was built by sponges and various skeletal algae (plus
bryozoans). Sponge reefs are at least as important in earth history as
coral reefs -- we now live in weird times where hardly any other organisms
than corals build reefs (but even nowadays, worms, vermetids, red algae,
etc. do!)...
- a reef must have some sort of "strength" against hydrodynamics
(elegantly circumscribed as wave-resistant) as loose associations of
organisms normally found in reefs may occur as well.  "Mudmounds",
large buildups of mud with an occasional skeletal organism, repeatedly
formed at greater depth throughout earth history but they only hardened
under the pressure of superposed sediments, i.e. not during their
"lifetime". And all of us probably agree that mudmounds are as little a
reef as a sand bank is...
Best wishes,
Markus
======================================================================
                      Markus Bertling, Ph.D.
                 Museum Curator and Collection Manager
            Geologisch-Palaeontologisches Institut und Museum
                          Pferdegasse 3
                        D- 48143 Muenster
                             Germany
e-mail: bertlin at uni-muenster.de         fax: ..49 - 251 - 83 248 91
                                      phone: ..49 - 251 - 83 239 42
                  http://www.uni-muenster.de/Geomuseum/
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