Dept. of Geological Sciences, Indiana
University, Bloomington IN47405. E-mail:
[email protected]
Abstract: Hurricane Control on Modern Reef Development.
Recent work on modern reefs around Grand Cayman has identified a
significant connection between
hurricanes and reef development. By
analyzing the architecture and anatomy of breakwater reefs around
Grand Cayman, I discovered that the reef core consists not of coral
framework, but of coral-rudstone layers whose large, abraded clasts
clearly implicate hurricanes as the major controlling agent. I also
discovered that the reef-crest is located a uniform distance (~300
m) from a mid-shelf scarp — a distance that is proportional to
the power and carrying capacity of hurricane waves. In addition to
breakwater reefs, I also analyzed architectural variation in a
submerged shelf-edge-reef system. This analysis showed that
inter-marginal variation in shelf-edge-reef architecture results
from the varying intensity of buttress pruning and sand flushing
during hurricanes. Furthermore, it showed that intra-marginal
variation in architecture is controlled by the angle of hurricane
wave approach. This connection
between
modern reef development and
hurricanes makes several testable predictions. First, the
relation
between
breakwater-reef position and shelf width predicts that
reefs should migrate along shore as sea-level rises and should
therefore show lateral variation in reef initiation dates. Second,
breakwater reef architecture should also vary as frictional
interaction
between
storm waves and shelf changes during sea-level
rise. Third, submerged shelf-edge reefs should show a predominance
of lateral accretion on margins exposed to fully-developed storm
waves and a proportionally greater vertical component as margins
become more protected. Fourth, the correlation
between
hurricane
intensity and shelf-edge reef architecture should also be reflected
in the ecological diversity of coral associations. And finally,
breakwater reefs and submerged shelf-edge reefs developed outside
areas of hurricane influence should have significantly different
styles of development.
AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas