The Franklin intrusions are an extensive swarm of late Hadrynian (latest Proterozoic) diabase dikes that occur in a giant arc from Great Bear Lake eastward to Melville Peninsula, Baffin Island, and northern Ungava. They are chemically and petrologically classified as tholeiites and are probably co-magmatic. Paleomagnetic pole positions and numerous whole-rock of K-Ar age determinations indicate that the dikes were emplaced at low paleolatitudes 650 m.y. ago. They intrude Hadrynian sedimentary sequences that contain features indicative of deposition under warm climatic conditions.

The Baffin dikes are subparallel with the northeast coastline of Baffin Island and a pronounced northwest-trending fault system. Intermittent, mainly normal, movement along these faults persisted from the Helikian to the Quaternary and produced a series of graben structures which may be due to the same regional tension as the dikes. Thus Baffin Bay and Davis Strait may have started to form as early as the late Hadrynian and may contain Paleozoic strata.

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