Tectonic evolution of the Durroon Basin, Tasmania

Abstract

The Durroon Basin containing up to 7 km of predominantly Cretaceous sedimentary infill is recognised on the basis of a different structural history to that of the adjacent Bass Basin. Structural development and sedimentation patterns of the Durroon Basin are the result of two distinct Cretaceous rifting episodes related to major regional tectonic events. The first episode (Otway Rift; 125?100 Ma) was a pronounced Late Jurassic (?)? Early Cretaceous rift phase during which volcaniclastic sediments were deposited in an elongate series of troughs formed by the initial separation of the Australian and Antarctic Plates. This stage was succeeded by a further rift phase which was responsible for much of the structural character of the Durroon Basin. The second extensional episode (Tasman Rift; 90?80 Ma), was caused by the opening and subsequent rapid development of the Tasman Sea. This episode created a series of post-depositional, detached, roll-over structures along margins formed by listric faults and formed updip culminations to tilted blocks. Post-Tasman Rift sedimentation was influenced by both Otway and Tasman drift. The effect was to cause subsidence to move to central parts of the Bass Basin, and by Early Tertiary times the Durroon Basin was buried beneath Cainozoic sediments of the Bass Basin.