[Coral-List] Definition of the Great Barrier Reef
Eugene Shinn
eshinn at marine.usf.edu
Tue Oct 16 13:31:06 EDT 2012
Thanks Ashley, Little wonder why the geography and geometry of the
GBR is so confusing to and outsider. You might be interested to know
that for the past 60 or more years the Australian GBR has served as
the model for the Lower Cretaceous Edward reef trend (also called
Stuart city trend) that circumscribes the northern Gulf of Mexico.
Geologists working on the Edwards reef trend, as I once did,
generally refer mainly to the narrow outer barrier of the GBR as the
modern model. The Edwards trend is often studied where it is exposed
in uplifted parts of Eastern Mexico. From there the reef extends
northward where the trend lies beneath southern Texas at a depth of
around 16,000 ft. In places it is more than 1000 ft. thick and is an
oil and gas-producing reservoir. The reef trend is around 12,000 ft.
beneath Louisiana where it curves southward under western Florida and
extends beneath the Everglades, and beyond. In Florida it is known as
the Sunniland trend. Oil was discovered in the reef trend near the
town of Sunniland in 1943. There are presently about a dozen small
producing oil fields in south Florida producing form the Sunniland
reef trend south east of Ft. Myers, Florida. Most Floridians have no
idea it is there. Like the GBR, there are patch reefs in paleo
landward positions behind the Edward reef barrier. Most are composed
of Rudistids and corals however I once spent a few weeks studying a
patch reefs exposed on the Blanco River in the Hill country of Texas.
That reef contained large coral heads we called Montastrea sp.
because they looked identical to the modern genus.
I write this to explain why geologists have long been so
interested in the geometry, and conditions under which modern coral
reefs serve as models for understanding ancient coral reefs. Even
before Oil and gas was discovered in ancient reefs it was mainly
geologists who studied coral reefs in Florida. The famous ones were,
T. Wayland Vaughan, and Alexander Agasssi. In the early 19 hundreds
geological knowledge was needed for the installation of offshore
lighthouses to guide and protect shipping from coral reefs. At that
time lighthouses were not erected to protect coral reefs. For all
these reasons the definitions of what constitutes a reef have been
endlessly discussed at geological conventions ever since I can
remember. Biologists did not begin dominating the study of coral
reefs until the mid 20th century although much biological study of
individual corals had been initiated by Mayor, Young, and Wells, a
few decades earlier. We should all thank Jacques Cousteau and SCUBA
for stimulating and facilitating the abundant biological study of
modern coral reefs we see today. Gene
--
No Rocks, No Water, No Ecosystem (EAS)
------------------------------------ -----------------------------------
E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eshinn at marine.usf.edu>
Tel 727 553-1158----------------------------------
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