Subduction complex melange of the Wandilla terrane, Palaeozoic New England Orogen, central Queensland, Australia

Devonian and Carboniferous rocks of the northern New England Orogen developed in a forearc setting in which the Wandilla terrane was part of the subduction complex. The Wandilla terrane shows three episodes of deformation. The first was associated with accretionary processes and formed lenticular and mudseam melange. Lenticular melange was derived from interbedded greywacke and mudstone, bedded chert and greenstone and shows progressive bedding-parallel extension with pinch-and-swell and boudinage. It is characterized by an alternation between zones of semi-coherent beds and zones with total bed disruption. Mudseam melange formed from thick-bedded greywacke units and is characterized by abundant mud injection features and scalloped greywacke contacts indicative of deformation of unconsolidated sediment and mobilization of overpressured mud. Both melange types formed at shallow structural levels in offscraped and imbricated successions. Lenticular melange resulted from stratal extension whereas mud-seam rocks were produced by the injection of overpressured mud into massive sands. The second and third deformations post-dated formation of the subduction complex and gave rise to a variably developed cleavage (S2) and steeply dipping strike-slip faults, respectively. © 1990.