Conclusions

Abstract The distribution of lithofacies in the Devonian Great Barrier Reef on the Lennard Shelf area is controlled by basement-hosted faults, with the reef and platform facies confined to palaeo-highs, clearly separated from basin facies in the abutting areas. These faults also focused syn-sedimentary deformation along the edge of the platform margin, with zones of sediment and cement-filled neptunian dikes forming above the basement faults and subsequently being reactivated during regional extensional deformation.From the interpretation of geophysical data and field work, the gross structural architecture of the Lennard Shelf is strike-extensive northwest-trending listric normal faults that parallel the basin margin and which show apparent offset on northeast-trending accommodation zones. The Limestone Billy Hills and Pillara Range of the Lennard Shelf are within a structural corridor of regional extent, perpendicular to the trend of the Fitzroy Trough. Meso-scale structures combined with the trend of the fault zone, consistently indicate that deformation is the result of a sinistral oblique-slip zone possibly above basement faults at depth. The deformation occurred within an accommodation zone between offset, regionally extensive northwest-trending normal faults which are parallel to the Fitzroy Trough margin. There is no evidence for compressional tectonics nor penetrative deformation as suggested by some earlier workers.