Coral Health and Monitoring Program
coral at coral.AOML.ERL.GOV
Wed Jul 5 15:45:36 EDT 1995
As part of our continuing effort to distribute information regarding
coral health and monitoring, we are circulating the following two
Bonem,-R.M. Recognition of storm impact on the reef sediment
al.-eds.. 1988. pp. 475-478.
Recognition of the imprint of hurricanes and other storm
deposits on the sediment record can provide a useful
stratigraphic marker for the study of modern and ancient reef
systems. Sediment cores were taken from lagoonal patch reef
and forereef settings along the north coast of Jamaica before
and after the passage of Hurricane Allen in August 1980.
Examination of these cores has revealed that preservation of
storm events is variable and may be altered with time.
Although storm layers were easily recognized in lagoonal
settings within 2 years following the hurricane, passage of
time has made recognition based on grain-size differences
more difficult due to bioturbation and grain-size alteration.
However, it was possible to identify storm sediments by the
presence of allochthonous skeletal grains.
Gagan,-M.K.; Chivas,-A.R.; Johnson,-D.P. Cyclone-induced
shelf sediment transport and the ecology of the Great
Barrier Reef. PROCEEDINGS-OF-THE-SIXTH-INTERNATIONAL-
P.;et-al.-eds.. 1988. pp. 595-600.
Shelf sediments collected immediately before and after the
passage of Cyclone Winifred (1 February 1986) confirmed that
the storm produced a normally graded layer extending 30 km
offshore in water up to 43m deep. Resampling of the storm
layer one year after the cyclone showed it to be completely
obliterated offshore, but well-preserved on the inner shelf.
The cross-shelf difference in preservation reflects the
concentration of benthic organisms and higher bioturbation
rates offshore. Post-cyclone changes in the cross-shelf
distribution of super(13)C/ super(12)C and carbonate suggest
that: (1) sediment derived from near-record flooding of the
Johnstone River did not move more than 15 km offshore, (2)
reef detritus was swept up to 1.5km shoreward to the mid-
shelf, and (3) resuspended mid-shelf sediment was driven at
least 15km shoreward to the inner shelf. Flood plume sediment
rarely reaches the Great Barrier Reef directly from shore.
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