Narooma Terrane

The Narooma Accretionary Complex or Narooma Terrane is a geological structural region on the south coast of New South Wales, Australia that is the remains of a subduction zone or an oceanic terrane. It can be found on the surface around Narooma, Batemans Bay and down south into Victoria near Mallacoota. It has attached itself to the Lachlan Fold Belt and has been considered as either an exotic terrane or as a part of the fold belt. Rocks are turbidites, block in matrix mélange, chert, and volcanics. The accretionary complex itself could either be the toe of a subduction zone, or an accretionary prism. It was moved by the Pacific Plate westwards for about 2500 km until it encountered the east coast of Gondwana. It is part of the Mallacoota Zone according to Willman, which in turn is part of the Eastern Lachlan Fold Belt, which is part of the Benambra Terrane.

The complex is made up of an imbricate stack in a sequence that is the same both at Narooma and Murruna Point, Batemans Bay. The top layer consists of turbidite sequence from the Early Ordovician. Below this is a high strain zone full of broken fragments. Special textures from the high strain zone include pressure solution, dilational veins and boudinage. Some of the rock appears as mylonite. Underneath the high strain is chert from the Late Cambrian to Late Ordovician.

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