Chris Fergusson Research Interests

Extensional and contractional deformation in the ancient Gondwanan margin of northeastern Australia

Joint research between Chris Fergusson, Bob Henderson (James Cook University, Townsville), Ian Withnall (Geological Survey of Queensland), Mark Fanning (Australian National University) and David Phillips (University of Melbourne).

The Tasman Fold Belt System in Queensland is largely covered by Palaeozoic to Quaternary sedimentary basin deposits. In north and central Queensland basement rocks are exposed in the Anakie Inlier, Charters Towers Province and southeast Georgetown Inlier. We have been undertaking research into the tectonic history of Neoproterozoic to Ordovician metamorphic rocks formed during and soon after the Middle Cambrian Delamerian Orogeny (Withnall et al. 1996). Many of these metamorphic rocks are affected by intense sub-horizontal foliation and may have formed in an extensional setting following earlier contractional deformation (see Fergusson et al. 2005). See references below for details.

The following photographs show the main S2 foliation in the Cape River Metamorphics, located 200 km southwest of Townsville. The last photograph shows a similar feature in the southern Anakie Inlier, 400 km south of Townsville.

S2 foliation in the Cape River Metamorphics with asymmetrical pressure fringe, Oxley Creek.

 

Oblique view across S2 foliation in the Cape River Metamorphics – strong intersection lineation (S1 – S2) is developed, Oxley Creek.

 

F3 folds in S2 Foliation, Cape River Metamorphics, Oxley Creek.

 

F3 folds and S3 crenulation cleavage in S2 foliation on the flat limb of a map-scale F3 synclinorium, Cape River Metamorphics, Oxley Creek.

 

Flat-lying S2 foliation axial planar to isoclinal folds in schist, Anakie Metamorphic Group, in the Oaky Creek area near the Clermont-Alpha Road.

Green et al. (1998) originally attributed this foliation to contractional deformation but it has been re-interpreted as reflecting extensional deformation by Fergusson et al. (2005). Studies of metamorphism to resolve this issue are on-going.

References

(Reprints for articles by Fergusson are available on request – cferguss@uow.edu.au)

Fergusson C. L., Henderson R. A., Lewthwaite K. J., Phillips D. and Withnall I. W. 2005. Structure of the Early Palaeozoic Cape River Metamorphics, Tasmanides of north Queensland: evaluation of the roles of convergent and extensional tectonics. Australian Journal of Earth Sciences 52, 261–277.

Fergusson C. L., Carr P. F., Fanning C. M. and Green T. J. 2001. Proterozoic-Cambrian detrital zircon and monazite ages from the Anakie Inlier, central Queensland: Grenville and Pacific-Gondwana signatures. Australian Journal of Earth Sciences 48, 857–866.

Green T. J., Fergusson C. L. and Withnall I. W. 1998. Refolding and strain in the Neoproterozoic Early Palaeozoic Anakie Metamorphic Group, central Queensland. Australian Journal of Earth Sciences 45, 915–924.

Fergusson C. L. and Green T. J. 1995. Structure of the Anakie Metamorphic Group and Fork Lagoon beds, southern Anakie Inlier, central Queensland. In: Withnall I. W. (ed.), 1995 Field Conference Clermont-Anakie Region Central Queensland, pp. 31–39. Geological Society of Australia, Queensland Division.

Withnall I. W., Blake P. R., Crouch S. B. S., Tenison Woods K., Hayward M. A., Lam J. S., Garrad P. and Rees I. D. 1995. Geology of the southern part of the Anakie Inlier, central Queensland. Queensland Geology 7, 245p.

Withnall I. W., Golding S. D., Rees I. D. and Dobos S. K. 1996, K-Ar dating of the Anakie Metamorphic Group: evidence for an extension of the Delamerian Orogeny into central Queensland. Australian Journal of Earth Sciences 43, 567–572.