Introduction to the special issue of Canadian Journal of Earth Sciences: The Nechako NATMAP Project of the central Canadian Cordillera.

The Canadian Cordillera in central British Columbia has seen the Mesozoic s ubduction of an oceanic terrane; the amalgamation of volcanic-arc terranes; continued intermittent Mesozoic compression and magmatism; and Tertiary wr enching, extension and magmatism. Except in its northernmost mountain range s, the area is extensively covered in glacial drift and thin veneers of Ter tiary volcanic rocks. In 1994, a group of scientists and technologists beli eved they could understand that cover, see through it, and discover the com ponents of that collision and extensional orogen. They would apply modern t echniques of isotopic and paleontological geochronology; lake-sediment, til l, and plant geochemistry; detailed gravity, magnetic, radiometric, paleoma gnetic, and electromagnetic surveys; and isotopic and trace element lithoch emistry, as they conducted extensive bedrock and surficial mapping. This sp ecial issue summarizes a cross-section of the scientific contributions deri ved from that mapping conducted under the auspices of the Nechako NATMAP Pr oject. It demonstrates the absolute necessity of applying modern isotopic a nd paleontologic geochronology to understand the Phanerozoic geology of the Cordillera. It emphasizes the necessity of detailed aeromagnetic surveys ( 500 m or less line spacing) in looking through covered terranes at anything more than 1 : 250 000 scale. And, it shows the immense utility of applying various geochemical techniques to solve geological problems and establish baselines for future research and economic development. Bedrock and surfici al mapping in the central Cordillera, using these and other techniques, hav e established the nature and timing of Mesozoic crustal growth, Tertiary cr ustal thinning, and the associated formation of mineral deposits.