| Abstract: | An interpretation of the MOIST seismic reflection profile along the north coast of Scotland has shown the pattern of deep crustal structure across the margin of the Caledonian orogen with the Hebridean cratonic foreland to the northwest. It is proposed that the lower crust of the orogen is characterised by a suite of easterly dipping thrusts that divide it into flakes that were imbricated during lateral compression of the lithosphere. The effects of concomitant and subsequent uplift and erosion led to the removal of the major part of the upper crust within the orogen so that the present crust and Moho are largely the relics of the Caledonian lower crust. As time progressed, the thrust front encroached further into the foreland and cut down to a basal décollement at successively deeper levels. This behaviour is explained as a consequence of the response of the brittle-ductile transition to changing the temperature regime, rock composition and strain rate as the orogeny proceeded. Palinspastic reconstructions of the whole lithosphere illustrate the process. Following the compressional phase of the orogeny, uplift led to initiation of extension and the reactivation of the thrusts as normal listric faults. Rotation of basement blocks gave rise to wedge-shaped sedimentary basins. |
