Events and sea-level changes on Gondwana's margin: The Meguma Zone (Cambrian to Devonian) of Nova Scotia, Canada
The Meguma Zone consists of thick, siliciclastic and volcaniclastic strata, and granitic plutons that underlie southern Nova Scotia and offshore areas. The strata were deposited from Late Cambrian through Early Devonian time on the continental margin of Gondwana. Grain size of the major stratigraphic units reflects the changing elevations of base level in the source region. Twelve major events in the zone can be related to changes in relative sea level and combined into four, second-order cycles. Each cycle consists of a fining-, then coarsening-upward sequence that is capped by subaerial volcaniclastic material. These subaerial events are assumed to represent significant hiati, and so are bounding unconformities. Two unconformities are at system boundaries; two, at sequence boundaries. Third-order cycles suggest idiosyncrasies of the source land. Ultimate cause of the Meguma cycles may be mantle activity that affected continental base level, relative sea level, and direction of continental drift. The Meguma curve is similar to that of northwest Africa.