Droughts - Extreme Events: A Physical Reconstruction and Risk Assessment - page 30

Salinity (parts per thousand)

0 20 100

60

1970

2410
2600
2970

100

Dolomite

4200
4630

Aragonite

200

5250

300

7850

8640

400

10 190

0.002 0.004 0.006 0.008

Molar Sr/Ca in ostracod shell

Figure 2.4. Salinity (Sr/Ca) record from ostracods in Lake Keilambete, Victoria,
Australia (after Chivas et al ., 1985 ).

Marine sediments

Layers of aeolian sediment have also been recorded in sea floor sed-
iments. De Deckker and Corrège (1991)identified layers of sand (grain size
> 60 µm) in a core from the Gulf of Carpentaria, Australia. They attributed these
sand layers to aeolian activity during arid phases of climate. Each of the lay-
ers was deposited approximately 2250 years apart, corresponding to arid phases
lasting on average 600 years and separated by wetter phases approximately 1500
years in length. The 2250 year arid cycles occurred during the Pleistocene (they
did not extend their core into the Holocene) when aridity or prolonged droughts
allowed the mobilisation of sand from what is now semi-arid terrain surround-
ing the western Gulf of Carpentaria region. The lower sea levels throughout