Significance of shallow core transects for reef models and sea-level curves, Heron Reef, Great Barrier Reef

Webb, Gregory E., Nothdurft, Luke D., Zhao, Jian-Xin, Opdyke, Bradley and Price, Gilbert (2016) Significance of shallow core transects for reef models and sea-level curves, Heron Reef, Great Barrier Reef. Sedimentology , 63 6: 1396-1424. doi:10.1111/sed.12266

Author Webb, Gregory E.
Nothdurft, Luke D.
Zhao, Jian-Xin
Opdyke, Bradley
Price, Gilbert
Title Significance of shallow core transects for reef models and sea-level curves, Heron Reef, Great Barrier Reef
Journal name Sedimentology    Check publisher's open access policy
ISSN 0037-0746
Publication date 2016-10-01
Year available 2016
Sub-type Article (original research)
DOI 10.1111/sed.12266
Open Access Status Not yet assessed
Volume 63
Issue 6
Start page 1396
End page 1424
Total pages 9
Place of publication Chichester, West Sussex United Kingdom
Publisher Wiley-Blackwell Publishing
Language eng
Abstract A sequence of shallow reef cores from Heron Reef, Great Barrier Reef, provides new insights into Holocene reef growth models. Isochron analysis of a leeward core transect suggests that the north-western end of Heron Reef reached current sea-level by ca 6·5 kyr bp and then prograded leeward at a rate of ca 19·6 m/kyr between 5·1 kyr and 4·1 kyr bp (pre-1950) to the present reef margin. A single short core on the opposing margin of the reef is consistent with greater and more recent progradation there. Further to the east, one windward core reached modern sea-level by ca 6·3 kyr bp, suggesting near ‘keep-up’ behaviour at that location, but the opposing leeward margin behind the lagoon reached sea-level much more recently. Hence, Heron Reef exhibited significantly different reef growth behaviour on different parts of the same margin. Mean reef accretion rates calculated from within 20 m of one another in the leeward core transect varied between ca 2·9 m and 4·7 m/kyr depending on relative position in the prograding wedge. These cores serve as a warning regarding the use of isolated cores to inform reef growth rates because apparent aggradation at any given location on a reef varies depending on its location relative to a prograding margin. Only transects of closely spaced cores can document reef behaviour adequately so as to inform reef growth models and sea-level curves. The cores also emphasize potential problems in U-series dates for corals within a shallow (ca 1·5 m) zone beneath the reef flat. Apparent age inversions restricted to that active diagenetic zone may reflect remobilization and concentration of Th in irregularly distributed microbialites or biofilms that were missed during sample vetting. Importantly, the Th-containing contaminant causes ages to appear too old, rather than too young, as would be expected from younger cement.
Keyword Coral reef
Reef growth models
Shallow core
U-series dating
Q-Index Code C1
Q-Index Status Provisional Code
Grant ID DP1096184
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
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