Geochronology of plutonic rocks and their tectonic terranes in Glacier Bay National Park and Preserve, southeast Alaska

A comprehensive geochronological study of plutonic rocks in Glacier Bay National Park and Preserve, southeast Alaska, reveals the temporal and spatial relationships between these rocks and their tectonic terranes. The research identifies six major plutonic belts and two nonbelt occurrences, spanning from Jurassic to Oligocene periods (201.6–23.0 Ma). These plutonic units are classified into 17 distinct age-compositional groups, with younger belts often superimposed on older ones. Almost all these rocks are linked to Cretaceous and Tertiary subduction events, intruding three geographic subregions: the Coastal Islands, Tarr Inlet Suture Zone (including the Border Ranges Fault Zone), and Central Alexander Archipelago. The study highlights that Early Cretaceous plutons primarily intrude the Alexander and Wrangellia terranes in the Central Alexander Archipelago, while Paleogene plutons intrude a broader range of terranes across all subregions. This research provides critical insights into the tectonic evolution of this UNESCO World Heritage Site, offering a detailed framework for understanding the geological history of the region.

Brew, D. A., Tellier, K. E., Lanphere, M. A., Nielsen, D. C., Smith, J. G., & Sonnevil, R. A. (2014). Geochronology of plutonic rocks and their tectonic terranes in Glacier Bay National Park and Preserve, southeast Alaska. Professional Paper. https://doi.org/10.3133/pp1776e