| Summary: | Five phases of deformation within six fault-bounded structural blocks are recognised in the Palaeozoic rocks of central Notre Dame Bay. The Lukes Arm-Sops Head (LASH) Fault, or Red Indian Line is a major sigmoidally shaped terrane-bounding fault in the Dunnage Terrane. The LASH Fault controlled deformation, which was protracted, progressive and heterogeneous. D0 involves wet-sediment deformation, is non-time specific and occurred during D1. D1 pre-Acadian structures include NW-SE to NNW-SSE upright macroscopic F1 folds, and local recumbent F1 folds related to SSV directed D1 thrusting. D1 structures were controlled by the restraining bend shape of the LASH Fault from mid-Ordovician time onwards. F2 Acadian folds trend NE-SW are transected by the anastomosing S2 cleavage, are upright, tight to isoclinal and trend NE-SW. F2 fold transection is related to the position of the fold with respect to the LASH Fault. S2 changes from a predominantly clockwise transection of F2 (<10°) to the south, through axial planar, to anticlockwise transected northwards towards the LASH Fault. D2 is interpreted to have formed under a N-S sinistral shear couple from early-Silurian time, with local dextral shear along E-W to ESE-WNW trending areas of the LASH Fault. F3 late-Acadian folds were associated with strike-slip faults, have a local axial planar S3 crenulation cleavage, and deform D1 and D2 structures about upright NE-SW axes. D2 to D3 transition was progressive in the late-Silurian, under widespread E-W dextral shear. D3 and older structures occur in rocks as old as Wenlock and are crosscut by Upper Ludlow dykes. Post-Acadian F4 folds are Devonian and are associated with kink bands that refold earlier structures about NW-SE axes. D5 involves complex crosscutting joints, faults, veins and shear arrays and ranges from Devonian to Jurassic.
|
|---|