2002—Origin and timing of the Miocene-Pliocene unconformity in southeast Australia

ABSTRACT: An unconformity is present close to the Miocene–Pliocene boundary in the onshore and nearshore portions of the Otway, Port Phillip–Torquay, and Gippsland basins of southeast Australia. The un-conformity is angular (generally, 1–58 angularity), with the under-lying Miocene units having been deformed (gentle folding and reverse faulting) and eroded prior to deposition of the Pliocene succession. The unconformity also marks a change from Oligocene–Miocene deposition of cool-water carbonate sediments and brown coal-bearing successions to the accumulation of more siliciclastic-rich sediments in Pliocene time. The Miocene–Pliocene boundary therefore represents an interval of significant regional uplift in the southeast Australian basins. The amount of section removed is greatest around the Otway and Strzelecki ranges in Victoria, where up to a kilometer of section may have been removed. In most onshore sections of the Victorian basins hundreds of meters of section have been eroded. In distal offshore locations th