Effects of temperature-dependent thermal diffusivity on shear instability in a viscoelastic zone: implications for faster ductile faulting and earthquakes in the spinel stability field

During the Mesozoic breakup of eastern Gondwana, rifting occurred along both the Southern Ocean Rift (SOR) between Australia and Antarctica, and the Tasman Sea Rift (TSR) between Australia and the Lord Howe Rise. As a consequence of breakup, Tasmania, located at the southeastern tip of Australia, is now surrounded by rifted margins, including a failed branch of the SOR within Bass Strait to the north. Apatite fission track (AFT) results from the Furneaux Islands, located along the Bassian Rise at the eastern edge of Bass Strait, record two major episodes of rapid cooling/denudation since breakup began. The first occurred during the middle Cretaceous at ~94±2 Ma and documents the timing of formation of the Bassian Rise. This was followed during the Early Tertiary by the second episode at some time between ~65¯45 Ma, possibly related to Pacific plate rearrangement and north Australian collision in New Guinea. Importantly, the AFT results indicate that formation of the Bassian Rise occurred during the middle Cretaceous at the same time as: (1) rifting along the TSR began, and (2) rifting along the SOR within Bass Strait ceased. This suggests a link between the timing of formation of the Bassian Rise and the initiation and cessation of major rifting events along the adjacent margins.