The Jindabyne thrust and its tectonic, physiographic and petrogenetic significance

The Jindabyne Thrust has been mapped south of Lake Eucumbene, along the eastern side of Lake Jindabyne and thence southwards to the gorge of the Snowy River in Byadbo Lands. It is marked by a crush zone and a west-facing scarp. Structure contours on the Thrust where it enters the gorge of the Snowy River in the Byadbo region indicate an easterly dip of about 20^°. The north-south erosional valley now occupied by Lake Jindabyne is controlled by the Thrust and the gorge below the Jindabyne Dam has been rejuvenated by recent movement. The nature of the Jindabyne Thrust and other faults in the Jindabyne-Berridale region can be deduced from their effects on the Silurian granitoid plutons. Where a pluton, circular or elliptical in plan and with vertical walls, is transected by a thrust, a semi-elliptical or semi-circular shape results; granitoid rock types cannot be matched across the fault. Wrench faults in the region either curve into or are transected by the thrusts, depending upon the geometrical relationships of both. It is suggested that the north-south dividing line between granitoids derived from igneous rocks (I-types) to the east and granitoids derived from metasedimentary rocks (S-types) to the west is a major tectonic feature of eastern Australia. The line coincides with a transition from a regime where wrench faulting predominates to one dominated by thrust faulting. These changes in both tectonics and granitoid lithology suggest that the I-S line marks the eastern boundary of crystalline basement, possibly of Precambrian age. Copyright.