Subduction‐related deformation and the Narooma anticlinorium, Eastern Lachlan Fold Belt, Southeastern New South Wales

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Abstract
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.