Continuing Abstracts

[Coral Health and Monitoring Program]

As part of our continuing effort to distribute information regarding 
coral health and monitoring, we are circulating the following two 
abstracts:   


Bonem,-R.M.  Recognition of storm impact on the reef sediment 
        record.  PROCEEDINGS-OF-THE-SIXTH-INTERNATIONAL-CORAL- 
        REEF-SYMPOSIUM,-TOWNSVILLE,-AUSTRALIA,-8th-12th-AUGUST- 
        1988.-VOLUME-2:-CONTRIBUTED-PAPERS-MINI-SYMPOSIUM-1-TO- 
        10-14. Choat,-J.H.;Barnes,-D.;Borowitzka,-M.A.;Coll,- 
        J.C.;Davies,-P.J.;Flood,-P.;Hatcher,-B.G.;Hopley,-D.;et- 
        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- 
        CORAL-REEF-SYMPOSIUM,-TOWNSVILLE,-AUSTRALIA,-8th-12th- 
        AUGUST-1988.-VOLUME-2:-CONTRIBUTED-PAPERS-MINI- 
        SYMPOSIUM-1-TO-10-14. Choat,-J.H.;Barnes,- 
        D.;Borowitzka,-M.A.;Coll,-J.C.;Davies,-P.J.;Flood,- 
        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.