Northern Cordilleran terranes and their interactions through time

Abstract

In the 25 years since the first application of the terrane concept to the North American Cordillera and the introduction of the term “suspect,” a pattern of interterrane stratigraphic and intrusive linkages and shared isotopic and faunal elements has emerged. Far from being restricted to late, postamalgamation overlaps, these linkages can be as old as the oldest rocks within the terranes. In the Canadian Cordillera, these linkages give a coherent sense to terranes that otherwise might appear to be a collection of isolated and unrelated fragments. Such observed linkages effectively eliminate some of the paleogeographic uncertainties that were previously inferred between adjacent terranes (although not necessarily with respect to the Laurentian continent) and highlight their common history. In light of these relationships, it is now possible to interpret terranes of the Canadian Cordillera in terms of shared geodynamic scenarios, such as repeated arc superposition on older arcs and/or basement and coexisting arc system components. A primary result of this analysis is that the Intermontane terranes represent one interrelated set of arcs, marginal seas, and continental fragments that once formed a Paleozoic to early Mesozoic fringe to North America, the peri-Laurentian realm. By contrast, the Insular terranes, along with the Farewell and Arctic-Alaska terranes, include crustal fragments that originated from separate sites within the Arctic realm in Paleozoic time.