Magnetic Basement

Magnetic basement is usually equated to crystalline (felsic and mafic) or sometimes, metamorphic basement. It is the unconformity upon which an essentially non-magnetic sedimentary section has been deposited. Large exposures of basement (e.g., the Canadian Shield) show it to be lithologically and magnetically heterogeneous. Very thick sequences of highly magnetic volcanics may sometimes be considered equivalent to a magnetic basement.