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

Abstract

COVERMount Fairweather (15,300 ft or 4,663 m) in the far distance beyond the peaks and glaciers that surround (and conceal) John Hopkins Inlet. The photo was taken from the complex metamorphosed Paleozoic rocks and Cretaceous plutons east of Reid Inlet looking across the Tarr Inlet suture zone and over the dominant metamorphosed Mesozoic rocks of the Fairweather Range. Mount Fairweather is underlain by layered gabbroic rocks of Tertiary age. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Geochronology of Plutonic Rocks and their Tectonic Terranes in Glacier Bay AbstractWe have identified six major belts and two nonbelt occurrences of plutonic rocks in Glacier Bay National Park and Preserve and characterized them on the basis of geologic mapping, igneous petrology, geochemistry, and isotopic dating. The six plutonic belts and two other occurrences are, from oldest to youngest: (1)

Cooling history of the St. Elias syntaxis, southeast Alaska, revealed by geochronology and thermochronology of cobble-sized glacial detritus

“…Mafic intrusions are not mapped within the study area but are known from a narrow mafic‐ultramafic belt farther southeast in the Fairweather Range and as far south as Chichagof and Baranof islands (Figure ). These intrusions have been interpreted as being associated with transpression at the Fairweather Fault [e.g., Rossman , ; Plafker and MacKevett , ; Loney et al ., ; Loney and Himmelberg , ; Brew et al , ]. As the St. Elias syntaxis area is extensively ice covered, hitherto undetected Oligocene mafic intrusions may occur in the Hubbard and Seward Glacier region as well, due to either in‐place intrusion or lateral displacement along the Fairweather Fault.…”