According to a new study led by Dr Joanne Whittaker of the University of Tasmania’s Institute for Marine and Antarctic Studies, the Australia’s island state, Tasmania, and the U.S. states of Idaho, Montana, the Canadian province of British Columbia, were close geographical neighbors about 1.4 billion years ago in the Mesoproterozoic supercontinent Columbia (also known as Nuna or Hudsonland).
Mount Wellington and Hobart Town from Kangaroo Point (Tasmania), by John Glover, 1834.
Dr Whittaker’s team age-dated minerals monazite and zircon, found in sedimentary rocks from the Rocky Cape Group in North West Tasmania.
The scientists found that these rocks were deposited in an ancient ocean between 1.45 and 1.33 billion years ago, making them the oldest rocks in Tasmania.
“The patterns of ages in the Rocky Cape Group strongly resemble those in sedimentary rocks from Montana, Idaho and southern British Columbia (the Belt-Purcell Supergroup rocks), which is a strong genetic fingerprint and evidence that the Rocky Cape and the Belt-Purcell rocks were geographically close 1.4 billion years ago,” explained Dr Jacqueline Halpin of the University of Tasmania, the first author of a paper published in the journal Precambrian Research.
At this time, both Tasmania and North America were part of the supercontinent Columbia.
“As plate tectonics and the supercontinent cycle started to rift Columbia apart, a large sedimentary basin formed that included the Rocky Cape Group and Belt-Purcell Supergroup rocks,” Dr Halpin said.
The continued breakup of Columbia eventually dispersed parts of this ancient sedimentary basin to opposite sides of the Earth.
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Jacqueline A. Halpin et al. 2014. Authigenic monazite and detrital zircon dating from the Proterozoic Rocky Cape Group, Tasmania: Links to the Belt-Purcell Supergroup, North America. Precambrian Research, vol. 250, pp. 50–67; doi: 10.1016/j.precamres.2014.05.025
Source link: https://www.sci.news/geology/science-tasmania-western-north-america-neighbors-02088.html
