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Fold-thrust Deformation

  1. Marlborough-Fitzroy area

Two fault styles dominate the Fitzroy region: Late Permian-Triassic thrusts and associated tear faults; and Cretaceous-Tertiary normal faults (Fig. 2). Significant post-Triassic strike-slip movement has also occurred on some of the faults in the region (e.g., the Broad Sound Fault). Many of the Cretaceous-Tertiary normal faults exploit the pre-existing thrust-tear fault architecture of the region to such an extent that almost all faults, of any age, have a Cretaceous-Tertiary brittle overprint. Many of the thrusts in Figure 2 are continuous with a normal fault that forms the boundary to an adjacent Cretaceous or Tertiary basin. Although there are undoubtedly elements of crustal fracturing in the region that controlled basin development during Early Permian extension (Hammond, 1987; Fielding et al., this volume), we have not positively identified any regional fault patterns within the NNEFB that can be associated directly with this event.

Contractional structures developed during the Permo-Triassic thrust event (thrusts, folds, cleavage) are pervasively developed for a distance of at least 100 km inland from the coast and continue with varying intensity into the Bowen Basin. Regional deformation related to this event is strongly heterogeneous. The most deformed terranes in the eastern part of the belt include remnants of the Devonian-Carboniferous accretionary terranes in the Coastal Block and parts of the Calliope terrane (Mt Holly Beds). Further west, the GOZ describes an arcuate shape in plan (Fig. 2) that includes a