Abstract
The Mt Fleming area has extensive exposures of strata of the Beacon Supergroun (Devonian-Late Triassic) and Ferrar Dolente (Early-Middle Jurassic) which dip 3-6° northwest. The area is crossed by a vertical northeast-striking fault which has a maximum throw of 270 m at the eastern end of Mt Fleming.The throw decreases southwestwards, reaching zero vertical displacement at Horseshoe Mountain. Drag folding associated with the fault has locally tilted strata to produce dips of up to 45°. The fault is considered to result from intrusion of a dolerite sill, at least 270 m thick, into lower Beacon Heights Ortho-quartzite,which is not exposed at Mt Fleming but forms bluffs in the Airdevronsix Icefalls 3 km to the east.The increase of throw northeastwards along the fault indicates intrusion of the sill from the NNE.