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Lily Pond
Wangi
Waterfall Creek (Gunlom)
35
40
0
5
10
15
20
25
30
Years x 1000 BP
Figure 3.7. Time lines including uncertainty margins from thermoluminescence
dates for plunge pool deposits at Lily Pond, Wangi and Waterfall Creek (Gunlom),
Northern Territory, Australia. Note the close correspondence between dates during
the Holocene Climatic Optimum (10--4 ka), the gap in sedimentation between 15
and 10 ka and the late Pleistocene sedimentation between 30 and 18 ka.
damming of streams. Ridge 1 at Wangi Falls returned luminescence ages extend-
ing from 3000 years BP till present and Ridge 2 produced ages from 30 000 till
4000 years BP. Like Gunlom, Ridge 2 at Wangi Falls shows a substantial hiatus
in sedimentation between approximately 17 000 and 9000 years BP. Ridge 2 at
Wangi Falls stands approximately 9 m above the present plunge pool beach and
150maway. Major flood episodes also deposit sediment on Ridge 1.
Athird site in the 'Top End' of the Northern Territory also revealed a near
identical flood history to Gunlom and Wangi Falls (Fig. 3.7). Baker and Pickup
(1987)identified a channel scabland on the sandstone plateau above Katherine
Gorge. Inspection of the site showed that flood flows have exceeded the capacity
of the 30 m deep section of Katherine Gorge in this reach and eroded a bedrock
channel into the plateau surface. In one location this bedrock channel narrows
significantly and immediately downstream of the constriction increased velocity
flows have eroded a large plunge pool like feature (Nott and Price, 1999). A small
( 3mhigh) waterfall or step in the bedrock floor lies at the upstream end of
the plungepoolandlikethe plunge pools at Gunlom and Wangi Falls a sand
ridge has been deposited to the side of the pool. There is only one ridge at this
location (Lily Pond) and no modern plunge pool beach. The ridge rises to 7 m
above the plunge pool mean water level and the modern plunge pool beach
probably forms the lower slope of the single existing ridge. Luminescence ages
from the crest of the ridge and further downslope again showed a major period
of sedimentation between 23 000 and 4000 years BP with a significant hiatus
between 17 000 and 8000 years BP. Ages from the lower part of the ridge slope
returned similar ages to those obtained from Ridge 1 at Gunlom and Wangi
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