This quartzite formed in a riverbed, as indicated by the well-developed cross-bedding (sedimentary layers at angles to the main horizontal layers). Its buff to gray color is typical of the oldest rocks of the Huronian Supergroup. The color suggests deposition when the atmosphere contained no free oxygen.
Topic: Earth Science
Keywords: Atmosphere, Geology, Stratigraphic--Huronian, Oxygen, Paleoclimatology, Quartzite