Relict Reefs

Paul Blanchon blanchon at
Thu May 29 13:18:35 EDT 1997

Dear Joanie and Bill (and list members),

I work on post-glacial reef development and have published on both relict
(drowned) reefs and active submerged reefs in the Caribbean-Atlantic reef
province. While I can certainly help in updating your list, it would be
useful to know exactly what you are looking for and why.

For example, there are several active submerged reefs in the Caribbean (see
Macintyre et al. '81 4th ICRS Manila 1: 567; Macintyre '91 Coral Reefs 10:
167; Fairbanks '89 Nature 342: 637) that I have argued are independent
structures that are accreting laterally and are prevented from growing to
sea level by hurricane pruning. Drilling data is consistent with this
hypothesis and shows they are composed of up to 12 m of deep water
framework -- more than enough to account for their present architecture
(Blanchon in press 8th ICRS Panama; Blanchon and Jones in press
Sedimentology June '97). Alternatively, there are many reports of relict
"breakwater" reef deposits composed of Acropora palmata in the Caribbean
(for summaries see Blanchon and Jones '95 J Coastal Res 11: 1-33; Blanchon
and Shaw '95 Geology 23: 1-4). Some of these relict breakwater reefs
provided substrate for subsequent submerged-reef development (eg Adey et al
'77, 3rd ICRS Miami 2: 15; Hubbard et al 86 J Sed Pet 56: 841) whereas
others remain uncolonized by deep water coral growth (eg Lightly et al 78;
Blanchon in prep).

If you accept the existence of both these reef types today, then such reef
types also probably existed in the past when sea level was at lower levels
(as shown by Fairbanks's data from Barbados). Without drilling data,
therefore, relict reef features recognized in deep waters could be either
type and consequently of little use for determining things like sea-level
position etc. Let me (and the list) know exactly what reef type you are
looking for and why, and perhaps we can come up with useful data to
supplement your compilation.

Cheers, Paul.

        Paul Blanchon Ph.D ||  Research Associate
        Department of Geological Sciences,
        1005 E. 10th Street,
        Indiana University,
        Bloomington, IN 47405-1403.
        Tel: (812) 855-9729 Fax: (812) 855-7899
        E-mail: blanchon at
        Visit the Reef Resource Page at:

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