Paleomagnetism of the Hervey Group, Central New South Wales and its tectonic implications

Abstract

Paleomagnetic work on the Hervey Group in southeast Australia reveals a predeformational magnetization as suggested by the retention of a predeformational compaction produced magnetic fabric and the effect of deformation on both the magnetic fabric and the direction of the magnetic remanence in cleaved rocks. The formation mean direction D=29.2°, I=−19.3° with α95=15.5° gives a latest Devonian‐Early Carboniferous palaeomagnetic pole at 54.4°S, 24.1°E with DP=8.4°, DM=16.2°. Comparing this pole with existing poles from Australia and North America, it is suggested that: (1) The Lachlan Fold Belt of southeast Australia has been part of cratonic Australia since at least the late Devonian, and consequently, the Late Palaeozoic palaeomagnetic data from the LFB may be applied to the whole of Gondwanaland. (2) Cratonic Australia and the New England Fold Belt were all in an equatorial position during the Early Carboniferous. (3) There was probably a rapid anticlockwise rotation of Gondwanaland during the Late Devonian around an axis close to Australia. (4) A “V”‐shaped ocean existed between Laurussia and the northern margin of western Gondwanaland during the late Devonian‐Early Carboniferous. The Appalachian‐Hercynian Orogenic Belt is probably the result of the closure of this ocean.