Structural elements of the southern Thomson Orogen (Australian Tasmanides): a tale of megafolds

摘要

Multi-scale, multi-method integration of geological constraints, with new interpretations of potential field data and seismic reflection data, has resulted in a comprehensive structural interpretation of the southern Thomson Orogen, eastern Australia. The interpretation reveals similar to 50 major faults and shear zones, many of which can be traced for several hundred kilometres. The interpretation suggests that the southern Thomson Orogen can be subdivided into several structural domains that can be distinguished by differences in: (i) spatial orientation, (ii) geographic distribution, and (iii) partly the timing of major faults, but also to varying degrees by (iv) the evolution and spatial orientation of other structural elements, such as folds, minor faults and fractures, (v) broader lithological trends, (vi) stratigraphy, and (vii) structural style. The two largest domains are the Western Structural Domain that contains numerous faults and shear zones, and the fold-dominated Eastern Structural Domain, which is more strongly affected by late- to post-Devonian thrusting than the Western Structural Domain. Notwithstanding their differences, the domains can be integrated into a coherent structural model for the southern Thomson Orogen, which suggests that the area represents a set of megafolds or oroclines, which may have formed during the Bindian Orogeny.