Honours Abstract (2005)
Peter MCMILLAN

The geology of the coastal outcrops from Chain Bay to Surfside in the Bateman's Bay area preserves a basal volcanic unit that is Cambrian in age (Burrewarra Point Formation). This is overlain by a chert with minor mudstone unit which is latest Cambrian to Middle Ordovician in age (lower chert of the Narooma Chert), this unit grades to chert interbedded with mudstone to a mudstone interbedded with siliceous mudstone and chert which is late Middle to Late Ordovician in age (upper part of the Narooma Chert). The Narooma Chert is overlain by a mudstone succession which contains areas of melange (Bogolo Formation). A turbidite unit (Adaminaby Group) which is Ordovician in age outcrops at Surfside.

The study area has undergone intense deformation associated with three recognised deformation events. D1 deformation is characterised in the study area by east-west trending folds which have limbs cut by cleavage associated with D2. The D2 deformation is associated with the strongest structural overprinting which is responsible for north-south trending isoclinal folds developed at several scales. This event has resulted in imbrication of units as a result of strong east-west compression. It resulted in steeply west-dipping units with a strong cleavage which also dips steeply to the west. D3 deformation is responsible for small scale chevron folding and kink bands. The different orers of folds preserved in the area are a result of a buckling mechanism. The melange in the Bogolo Formation in the study area is interpreted to be a result of soft sediment deformation, shearing and localised diapirs that intruded up faults and/or areas of weakness.