Subduction-related deformation and the Narooma anticlinorium, eastern Lachlan Fold Belt, southeastern New South Wales

The Narooma anticlinorium is a north-plunging, apparent antiformal structure within imbricated turbidite, chert, basalt and melange of mid-Cambrian to Late Ordovician age. Younging in the turbidites and fold vergence in both chert and turbidite indicate that the anticlinorium is not a simple antiformal Fold. Complexity relates to superposition of early structures (subduction underplating) by late structures (wedge shortening). Early Silurian? subduction was responsible for a bedding-parallel fabric (S*), isoclinal recumbent folding, imbrication and broken formation. Superimposed crenulation cleavages, refolding of early folds, late-stage high-strain zones and brittle faults are part of mid-Silurian to Middle Devonian subduction-related, progressive deformation responsible for shortening in the accretionary 'wedge'. At this time the Narooma anticlinorium developed progressively above a gently west-dipping, subduction-related detachment fault by a combination of fold-amplification above a splay fault, localised wrenching and backthrusting. The eastern Lachlan Fold Belt records structural evidence for subduction at the macro- and mesoscopic scales from at least the Early Silurian to possibly the Middle Devonian.