Pre-Devonian stratigraphy and structure of theudPrion Beach-Rocky Boat Inlet-Osmiridium Beach coastal section, southernudTasmania

摘要

The pre-Devonian stratigraphy of the Prion Beach to Surprise Bay area is composed ofudfour stratigraphic units. The oldest is a (?) Precambrian, slightly metamorphosed,udmassive dolomite. This is in part the source area for three overlying units of theudDenison Group (Late Cambrian to Early Ordovician). The Tyler Creek Beds are highly serpentiniticudconglomerate, sandstone and siltstone. The Point Vivian Formation is audsequence of dolomitic siltstone and matrix rich polymictic conglomerates with a wide rangeudof depositional features including channels, graded bedding and slump structures. It wasudprobably deposited in a slope environment. The overlying Wierah Formation (Denison Group)udis composed of quartz-rich pebbly sandstones and quartz arenites which formed in a highudenergy environment possibly above wave base. Two shear zones cut across this stratigraphyudproducing transposed layers and boudins. At least one of these shear zones was activeudduring sedimentation and forms the western limit of the Point Vivian Formation in this area.