Interpreting New England subduction complex rocks using deep-sea drilling results from the Nankai Trough (offshore southwest Japan)

Two distinct structural styles are considered likely to have affected parts of the subduction complex of the New England Orogen. Imbricate thrusting, as occurs by duplexing at a ramp along the décollement at the base of the subduction complex, accounts for the structure of units such as the Gundahl Complex (also the Wandilla Formation of central Queensland and the Sandon beds of the Armidale district). These units have relatively straight-forward imbricate structure although in the case of the Gundahl Complex the thickness of units is condensed and reflects factors controlling deposition on the ocean plate and in the trench. In comparison units such as the Coramba beds contain excessively thick sections of turbidite wedge deposits that only seem explicable by complicated internal imbricate thrust repetition perhaps requiring earlier thrusts being cut by out-of-sequence thrusts. Much more age control than presently exists is required to improve our understanding of the sedimentary and structural processes that have developed these units. Deep-sea drilling and study of modern subduction zones, such as the Nankai Trough, provides an essential starting point for the interpretation of ancient subduction complexes.