Rb-Sr dating of Asgard Formation rocks from the Lower Wright Valley and Victoria Valley to determine the age of the oldest basement rocks in the Ross Dependency

The Asgard Formation in the Dry Valleys is a series of metamorphosed sedimentary rocks that form the oldest basement in this sector of the Transantarctic Mountains. Two weeks were spent in the Lower Wright Valley (near the Meserve Glacier Hut) and Victoria Valley (near Lake Vida) covering on foot the exposed outcrop areas of the Asgard Formation, medium high grade metamorphosed sedimentary rocks which are the oldest known rocks in the Dry Valley region.

Fifty five representative whole rock samples (each about 2kg) of quartz- and mica schists were collected for rubidium-strontium dating to determine their age of metamorphism. In preparation for Rb-Sr analysis, the rock samples were crushed into a fine powder suitable for x-ray fluorescence analysis of Rb and Sr concentrations and mass spectrometric isotopic analysis of Sr. Detailed petrographic descriptions were made of the specimens.