Timing of Gondwana break-up revealed
01 April 2011
Fresh evidence has been revealed on the timing of the break-up of the eastern margin of the super continent Gondwanaland to create Australia's east coast and New Zealand.
The evidence is contained in rock samples retrieved from the northern Lord Howe Rise about 1000 kilometres south east of Brisbane as part of a joint Australian/French marine survey to investigate the potential for petroleum resources in the region.
Geoscience Australia's Sensitive High Resolution Ion MicroProbe (SHRIMP) established the age of two volcanic rock samples from the Lord Howe Rise as 97 and 74 million years old. These ages correspond with the timing of volcanic events associated with the break-up of eastern Gondwana identified in eastern Australia, the southern Lord Howe Rise and New Zealand.
Seismic data from the Lord Howe Rise contains reflections and geometries which are consistent with those expected for volcanic rocks, suggesting that the dated rock samples are part of a more widespread phase of volcanism during the Late Cretaceous.
Geoscience Australia scientist, Dr Riko Hashimoto said that this regional volcanic activity was likely to be a precursor to the opening of the Tasman Sea, a scenario which appears to be supported by the results of the SHRIMP analysis.
"The new results provide an important insight into the final stages of the break-up of eastern Gondwana," Dr Hashimoto said.
"The dating provides evidence which is consistent with the continuation of a volcanic belt extending at least from the Whitsunday Islands to New Zealand through the length of the Lord Howe Rise during the Late Cretaceous," he said.
"These findings have contributed significantly to an assessment of the geological evolution and petroleum prospectivity of Lord Howe Rise," Dr Hashimoto said.
More information on the survey of Lord Howe Rise is available in AusGeo News.
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