THE STRUCTURE OF KANGAROO ISLAND, SOUTH-AUSTRALIA - STRAIN AND KINEMATIC PARTITIONING DURING DELAMERIAN BASIN AND PLATFORM REACTIVATION

Kangaroo Island forms the southern part of the Fleurieu are-segment of the Adelaide Fold-Thrust Belt. The Island consists of three structura lly distinct lithotectonic domains. In the southern zone basinal and r egionally metamorphosed Cambrian Kanmantoo Group strata are deformed b y regional southwest-trending folds and thrusts. The Kangaroo Island S hear Zone forms a broad east-west-trending strongly transposed zone, w hich consists of anastomosing mylonitic phyllonites. Along this shear zone the basinal strata are transpressionally displaced towards the no rthwest. Most of the exposed hangingwall of the shear zone is formed b y a regional-scale northerly overturned anticline, and parts of the fo otwall are also overturned. The northern zone forms a 15 km wide forel and thrust belt incorporating a veneer of Cambrian platformal sediment s, that overlie the southernmost extension of the Gawler Craton in Sou th Australia. These rock types, which are absent on the Fleurieu Penin sula mainland, are displaced along discrete north-vergent thrusts and reverse faults. The lithotectonic domains of Kangaroo Island reflect a basin evolution which is geometrically and in part also sedimentologi cally distinct from the mainland. The original geometry of the east-we st oriented basin appears to be the principal factor that controlled t he structural partitioning between the lithotectonic domains of Kangar oo Island during the Cambro-Ordovician Delamerian Orogeny, which resul ted in basin inversion and northwest-directed contraction.