Lower Paleozoic carbonatites associated with the St. Lawrence graben system are correlated with carbonatites of similar age (565 m.y.) in Greenland and Scandinavia. The correlation is well established in Canada where the intrusions all occur along a continuous rift system. The reconstruction of the whole province is made possible by restoring the continents to the positions they occupied prior to their separation.The combination of unique petrologic character, age, and structural setting shows that these rocks belong to a single alkaline rock province, defined by a rift system extending at least from central Canada to eastern Sweden that was active throughout its length about 565 m.y. ago.Periodic intrusion of alkaline rocks has occurred later, on both continents, associated with the components of the fracture system. In eastern Canada, alkaline rocks occur locally with ages of 520, 450, 300, and 110 m.y. in addition to the widespread 565 m.y. event.