Australia: The Land Where Time Began

A biography of the Australian continent 

Capricorn Orogeny

2.0 - 1.8 Ga (billion years ago)

This orogeny is thought to have occurred as the result of the convergence and eventually the collision of the Pilbara Craton and the even more ancient Yilgarn craton. According to Cawood & Tyler (2004), this orogeny was initiated in the Palaeoproterozoic during the suturing of the 2 cratons together in the formation of the West Australian Craton. This orogen is comprised of Palaeozoic plutonic rocks and rocks of the Gascoyne Complex, that are medium to high grade metamorphic, a number of Palaeoproterozoic volcano-sedimentary and sedimentary basins, such as the Ashburton, Blair, Yeffida, Bryah, Padbury and Earaheedy Basins, and the deformed margins of the Pilbara and Yilgarn Cratons. During the Ophthalmian Orogeny, about 2200 Ma, there were major pulses of deformation and metamorphism, also during the Glenburgh Orogeny, about 2000-1960 Ma, and the Capricorn Orogeny, about 1830-1780 Ma. There was also another, smaller, more localised event that is unnamed, at the end of the Palaeoproterozoic (similar to 1670-1620 Ma).

Repeated intracratonic reactivation has occurred, with renewed basin formation, magmatism and orogeny at this orogen from the Mesoproterozoic to Neoproterozoic. The Edmund and Collier Basins (Bangemall Supergroup), deformed during the Edmundian Orogeny of the Neoproterozoic, overlie unconformably the exhumed components of the orogen from the Palaeoproterozoic. The northern margin of the orogen was affected by the Ophthalmian Orogeny and the southern margin was affected by the Glenburgh orogeny.

A foreland basin developed along the margin of the Pilbara Craton as a result of the Ophthalmian Orogeny, and the Glenburgh Orogeny is associated with the accretion of the Glenburgh Terrane of the Gascoyne Complex, an allochthonous element, to the northwestern margin of the Yilgarn Craton.

A younger limit was set for the amalgamation of the Yilgarn and Pilbara cratons by the Capricorn Orogeny. The effects of the Capricorn Orogeny stretched across the entire orogen. Along the northern and southern margins of the orogen during this event, a number of basins developed that filled with sediment derived from the Yilgarn Craton, the Gascoyne Complex and a terrane from the Palaeoproterozoic that is not exposed at present.

In Australia and around the world, a major phase of collision corresponds to the Capricorn Orogeny. According to Cawood & Tyler, this appears to mark a major phase of assembly of a supercontinent.

According to Kearey et al., (2009) the history of episodic rifting, followed by multiple episodes of contraction and collision indicate at least 1 Wilson cycle, and possibly 2, during which ocean basins opened and closed in the Late Archean-Early Proterozoic (Cawood & Tyler, 2004). Kearey suggests that similar collisional orogens in Laurentia, Baltica, Siberia, China and India indicates the mid-Early Proterozoic was a time of supercontinent formation by means of plate tectonics.

Sources & Further reading

  1. Assembling and reactivating the Proterozoic Capricorn Orogeny: Lithotectonic elements, orogenies, and significance (Cawood & Tyler, 2004)
  2. A.P. Kershaw, H.A. Martin, & J.R.C. McEwan Mason, Hill, Robert S., (ed.), 1994, History of the Australian Vegetation, Cambridge University Press.
  3. Kearey, Philip, Klepeis, Keith A. & Vine, Frederick J., 2009, Global Tectonics, 3rd Edition, Wiley-Blackwell.
Author: M. H. Monroe
Last Updated 05/11/2008



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