The four principal sills, Basement, Peneplain, Asgard, and Mt. Fleming, are chemically and physically interconnected, forming a magmatic mush column, albeit being only observable for some 4 km downward in the crust, but the system may well extend downward through the entire continental crust. The distribution of MgO vertically through the Basement and Peneplain sills indicate that the filling point was in or about Bull Pass. And these profiles indicate that the episodes of emplacement were pulsatile, stopping and starting. Similarly, the upper, apparently much more featureless sills, when examined in detail also shown a history of piecemeal development through a series of multiple injections.