TERRANE TECTONICS: WHERE HAVE WE COME FROM AND WHERE ARE WE GOING?

The development of the terrane concept and tectonic syntheses derived from it was arguably a major advance in the understanding of Cordilleran tectonics, yet the methods carried intellectual baggage that have led to seemingly unresolvable paradoxes. In this presentation we review original concepts presented in terrane analysis, note pros and cons of the method, and present examples of where the methods shone and greatly advanced our understanding of a region’s history, and examples of where the method failed. We also consider examples of cases where a “house of cards” developed, in which tectonic models are based on accumulations of interpretations such that the interpretations became akin to observations. One example of misuse of terrane nomenclature results in excessive “splitting”, a particular problem in major fault zones and subduction complexes; taken to an extreme, every block in a mélange could be a picoterrane. The other type of extreme produced by some terrane terminology occurs when overzealous correlations lump assemblages with limited primary stratigraphic continuity via inferred correlations across complexly deformed zones. The latter is a particularly significant divergence from the original concept of “suspect terranes” where the burden of proof of correlation was a hard rule. We contend many of these problems are resolvable if researchers return to key areas, freed from blinders imposed by previous syntheses, and deploy a full suite of modern methods focused on resolving key issues.