A NEW TECTONIC MAP OF ALASKA NORTH OF 60°

A tectonic map that portrays the distribution and timing of deformational structures in Alaska north of 60°N has been prepared at a scale of 1:5,000,000. The map is constructed as a contribution to the Tectonic Map of the Arctic, part of an atlas of maps compiled by the geological surveys of Circum-Arctic countries with support from the UNESCO Commission for the Geological Map of the World (CGMW). For Alaska, deformational events fall into fourteen age intervals ranging from Neoproterozoic to late Neogene. Most of the map units represent areas of contractional deformation that were classified by age, but without regard to deformational styles that range from penetrative deformation to wide-spaced thrust belts to low-displacement fold belts. Although domains of brittle extensional deformation are commonly difficult to delineate in Alaska, areas with penetrative extensional structures are tectonically significant and their distributions are mapped separately. Following the conventions of the Tectonic Map of the Arctic, the distributions of ophiolites, basalt-chert terranes, volcanic arcs and plutonic complexes, metamorphic belts with grade of metamorphism, accretionary belts, post-tectonic basins and significant folds and faults are also portrayed. The map was compiled using the “Geologic Map of the Arctic” by Harrison and others (2011, doi: 10.4095/287868) as a base and assembled as a GIS project. The distribution of the deformations is principally based on original maps, outcrop to map-scale structures, and fission-track and isotopic cooling ages from published and unpublished sources. The map reveals that Alaska consists of numerous overlapping deformational events that include structures developed prior to terrane accretion, as a course of terrane accretion, and during post-accretion events.