The transition from salt diapir to weld and thrust: Examples from the Northern Flinders Ranges in South Australia

The interactions between salt diapirs, thrust welds and thrusts in contractional belts are poorly understood due to, first, the inability of seismic data to distinguish or resolve associated sub-resolution deformation, second, paucity good field examples. Warraweena area Northern Flinders Ranges South Australia contains examples Neoproterozoic Early Cambrian squeezed diapirs linked by steep reverse faults formed during Delamerian Orogeny. Benefiting from exposures, we use geological mapping, cross-section construction conceptual structural models assess three-dimensional geometry evolution structures, lateral transition linking variability meso- small-scale deformation. Three discrete consist narrow outcrops Callanna Group megabreccia (Willouran age) up 5-km long. Their diapiric origin is confirmed local development caprock, steepening flanking strata composite halokinetic sequences reworked diapir roof debris adjacent strata. surrounding rocks display only background levels In contrast, show no evidence precursor diapirism, have fault-related anticlines 100s m wavelength their hanging walls, an increase deformation (i.e. millimetre metre scale folds, fractures shear fabrics). transitions occur within less than 200 as short at terminations. exposed structures analogous those found on subsurface other basins such Gulf Mexico Atlantic conjugate margins. results this work can aid geoscientists evaluating three-way traps against faults, help them predict style abundance both that below resolution.