What is the Green River Formation?
Q: What is the Green River Formation?
A: The Green River Formation is an Eocene rock formation on the eastern side of the Rocky Mountains. It records sediment from a group of intermountain lakes. Its fine fossils make this a lagerstätte, a place of exceptional preservation.
Q: How old is the Green River Formation?
A: The various fossil beds of the Green River Formation span a 5 million year period, dating to between 53.5 and 48.5 million years ago (mya).
Q: What type of climate did it experience during its formation?
A: During its formation, the climate moved from the moist early Eocene climate and slightly drier mid-Eocene.
Q: How are sediments deposited in this formation?
A: Sediments are deposited in very fine layers, in pairs called varves which represent one year each - a dark layer from the growing season and light-hue inorganic layer in winter.
Q: What is the mean thickness of a varve here?
A: The mean thickness of a varve here is 0.18 mm, with a minimum thickness of 0.014 mm and maximum of 9.8 mm.
Q: Where is this formation located?
A: The sedimentary layers were formed in an area named after present-day Green River, which is a tributary of Colorado River located near Uinta Mountains in northeastern Utah
