Geoscience Reference
In-Depth Information
(a)
(b)
Great Barrier Reef
Princess Charlotte
Bay
5
4
3
2
1
20
21
1
6
15
16
19
9
2
3 & 4
17
Gulf of
Carpentaria
10
22
14
12
8
7
5
18
11
13
Curacoa
Island
Cairns
0 200 400
3
North-east
Australia
3 00 km
2
2
8
11
4
3
5
1
6
10
12
9
7
1
0
0 400 800
Distance from shore (m)
Supratidal mudflats
Case Fig. 10.1B Dated chenier-ridge sequences after Nott & Hayne (2001). Study sites and storm deposit data: (a) location
map of study sites; (b) stratigraphical relationship of storm deposit/ridges on Curacoa Island (top) and Princess Charlotte Bay
(bottom). Successive storm deposits are numbered accordingly. Mean reservoir-corrected radiocarbon age (in yr BP) for each
ridge is shown above traces. Note progressive increase in age with distance inland. AHD is Australian Height Datum.
category 3) comprise a moderately well sorted, graded bed of terrigenous sand-mud, locally
with a basal shell lag, and 5-20 cm in thickness (Gagan et al. 1988), which was remixed by
bioturbation within 12 months. The c . 4 m thick Holocene inner-shelf sediment prism at
Cairns thus represents the stratigraphical equivalent of about 40 category 3 cyclones, implying
a recurrence interval of c . 140 yr.
On the Cairns middle shelf, a series of five radiocarbon dates from a core located in 40 m
of water near Green Island, shows several storm beds in the past 1800 years preserved at an
average interval of 360 years, and in nearby cores average intervals are up to 600 years, indicat-
ing the generally erosive nature of the middle shelf 'cyclone corridor'. Thus, stratigraphical
information from shelf cores and chenier ridges indicates an average return interval for major
cyclones (category 3 or higher) of between 150 and 300 yr. Although recurrence intervals
and magnitudes will be different, similar processes and products are likely to occur on other
tropical storm-influenced shelves, and perhaps other 'rimmed' shelves such as Belize and New
Caledonia (section 10.2.3.6), although there are relatively few data on such issues to date.
The long recurrence intervals and high magnitudes of such disturbances are important con-
siderations for managers of shelf environments, such as the Great Barrier Reef Marine Park
Authority, who in their zoning scheme define allowable human use of different parts of the shelf
(section 10.5.2.1).
Relevant reading
Carter, R.M., Larcombe, P., Liu, K., et al. (2002) The Environmental Sedimentology of Trinity Bay, far North
Queensland . Final Report, James Cook University and Cairns Port Authority, 97 pp.
 
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