In the northern Flinders Ranges, Neoproterozoic and Cambrian sedimentary rocks were deformed and variably metamorphosed during the ca 500 Ma Cambro‐Ordovician Delamerian Orogeny. Balanced and restored structural sections across the northern Flinders Ranges show shortening of about 10–20%. Despite the presence of suitable evaporitic detachment horizons at the basement–cover interface, the structural style is best interpreted to be thick‐skinned involving basement with only a minor proportion of the overall shortening accommodated along stratigraphically controlled detachments. Much of the contractional deformation was localised by the inversion of former extensional faults such as the Norwest and Paralana Faults, which both controlled the deposition of Neoproterozoic cover successions. As such, both faults represent major, long‐lived structures which effectively define the present boundaries of the northern Flinders Ranges with the Gawler Craton to the west and the Curnamona Craton to the east. The most intense deformation, which resulted in exhumation of the basement along the Paralana Fault to form the Mt Painter and Babbage Inliers, coincides with extremely high heat flows related to extraordinarily high heat‐production rates in the basement rocks. High heat flow in the northern Flinders Ranges suggests that the structural style not only reflects the pre‐Delamerian basin architecture but is also a consequence of the reactivation of thermally perturbed, weakened basement.
The Olary Block comprises a set of Palaeoproterozoic to Mesoproterozoic basement inliers that were deformed together with the Neoproterozoic sedimentary cover of the Adelaide Geosyncline during the ca 500 Ma Cambro-Ordovician Delamerian Orogeny. Balanced and restored structural sections across this region show shortening of less than 20%. These basement inliers represent the interface between a region of thick-skinned deformation bordering the Curnamona Craton to the north and a region of thin-skinned deformation to the south and west in the Nackara Arc. The basement inliers represent upthrust segments of the subsided basin margin with the sedimentary package thickening to the south and to the west. Earlier formed extensional faults provided the major strain guides during Delamerian shortening. An early phase of east-west shortening is interpreted to be synchronous with dextral strike-slip deformation along basement-relay structures (e.g. Darling River lineament). During progressive shortening the tectonic transport direction rotated into a northwest to north direction, coeval with the onset of the main phase of thin-skinned fold deformation in the adjacent Nackara Arc.
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