Geodynamic significance of the boundary between the Thomson Orogen and the Lachlan Orogen, northwestern New South Wales and implications for Tasmanide tectonics

Interpretation of deep seismic reflection profiling, coupled with forward modelling of gravity and aeromagnetic data, new zircon U–Pb dating and the interpretation of the basement geology beneath the southern margin of the Eromanga Basin, has provided insights into the southern part of the underlying Thomson Orogen and its relationship with the Lachlan Orogen to the south. Our interpretations of these data suggest that the northern Lachlan and southern Thomson orogens had a shared history from the mid-Silurian to the Carboniferous. Major older differences, however, are suggested by the presence in the southern Thomson Orogen of: (i) a possible Neoproterozoic arc, (ii) latest Cambrian to earliest Ordovician turbidites, (iii) Late Ordovician turbidites, and (iv) geophysical evidence for thrusting of reflective ocean crust rocks high into the crust on a north-dipping detachment. The seismically imaged, north-dipping, crustal-scale Olepoloko Fault corresponds to the ‘surface expression’ of the Thomson–Lachlan...