Comparisons of the 2005 Geologic Map of North America with the 1965 Map, Areas 1-4
1. Alaska and parts of northwestern Canada
Principal differences between the 1965 map and the 2005 map are:
- Refinement of detail especially in the sedimentary rocks of the Brooks Range (A) and the Yukon Territory (B), and the depiction of the complex fold and thrust belts in these regions
- The addition of major terrane-bounding strike-slip and thrust fault such as the Kobuk-Malemute (C), Tintina (D), Border Ranges (E), Contact (F), Fairweather (G) and Aleutian megathrust (H). These structures, plus the Denali fault (I), which is shown on the 1965 map, comprise much of the framework for modern interpretations of the assembly of terranes in this part of the continent.
- Subdivision by age and composition of the plutonic rocks of the Coast batholith (J) and neighboring plutons, all of which are shown as Cretaceous intrusive rocks on the 1965 map, but which are now known to range in age from Triassic to Paleogene, and in composition from gabbro to true granite.
- Depiction of seafloor features, including the Aleutian megathrust (H), seamount chains (K), oceanic crustal isochrons (L), and transform faults, all of which are critical to understanding the history of terrane assembly.
Return to comparisons of map areas 1-4.
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