The mafic layered rocks of the Bushveld Complex are 6-8 km thick and outcrop over an area of 65 000 km 2 . The mafic sequences in the western and eastern limbs are remarkably similar, which suggests that they formed within a single magma chamber. Yet previous interpretations of the Bouguer gravity anomalies negate the possibility that they could be connected at depth. These gravity models are inadequate as they do not consider the isostatic response of this huge mass of mafic rock on the crust. Isostatic readjustment caused the base of the crust to be depressed by up to 6 km. In terms of this model it becomes possible to construct a gravity profile, consistent with observed data, which includes a 6-8 km-thick sequence of mafic rocks a mere 11 km deep in the crust, connecting the western and eastern limbs of the Bushveld Complex, where there is no central positive gravity anomaly.

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