Karen G. Jensen wrote (in part):
> Currently as far as I am aware, the most accepted model for Capitan Reef is
> that it is an underwater bank. I have heard that there is a new publication
> coming out this spring as SEPM Concepts in Sedimentology and Palentology
> No. 8, entitled "Geologic Framework of the Capitan Reef" the editors are
> Art Saller and Paul M Harris. It will probably present a variety of
> opinions.
The difference between a reef and a bank is often one of degree and/or semantics.
The Great Bahama Bank has fringing reefs, for example. The Capitan structure
contains evidence of shallow water construction, abundant sea floor cementation,
and evidenc of significant relief above the seafloor, especially the basin. This
sounds like a reef to me. For something that size reef or bank complex may be a
better term.
> Aside from Capitan Reef, other structures once interpreted as reefs have
> been reinterpreted as debris flows. For example, you could look at
> Mountjoy EW, Cook HE, Pray LC, McDaniel PN. 1972. Allochthonous carbonate
> debris flows worldwide indicators of reef complexes, banks or shelf margins
> Stratigraphy and Sedimentology, International Geological Congress, 24th
> Session, Section 6, p 172-189, which describes five examples.
Of course there are some things that have been called in situ reefs in the past
which are now recognised as debris flows. Why were they identified as reefs?
Because they are made of of reef rocks which are characteristically organically
bound limestones and/or with abundant evidence of early cementation. But where did
those blocks come from? From parental reefs, or reef environments where there was
not large single reef mass, but a collection of patch reefs, some of which ended up
sliding down into deeper water. In every case that I know of, including the paper
you cite, the blocks in the debris flow blocks (some of which are huge-live climbed
some of them) were transported down slope by mass movement from the main reef
mass where they were formed. In some cases the original reef they came from is
exposed, in some cases not. For every "reef" now identified as a transported block
there are dozens or hundred recognised as being in place. Every block of
transported reef rock points to a precurssor reef.
> Karen
In Christ
Jonathan