All of this raises the question of what a snowballing Earth would have looked like inside the continents. A team of US-based geologists believes they have discovered glacial deposits in the form of the so-called Tabaqib Sandstone in Colorado. These sandstones are found along the Front Range of the Rocky Mountains, including the area just west of Colorado Springs. And if the authors’ interpretation is correct, they were formed under the ice of a huge glacier.
There are many ways to form sandstone deposits, but because sandstone is a collection of remnants of much older rocks, it can be difficult to date. But in this case, the Tavakaib sandstone is interrupted by intrusions of dark rock containing large amounts of quartz and hematite, a type of iron oxide.
These intrusions can teach us many surprising things. First, some process must have exerted enough force to force material through small faults in the sandstone. Hematite is deposited only under very specific conditions. This will give you more information. And, most importantly, hematite can trap uranium and lead as it decays to lead, providing a way to date when deposits formed.
under the snowman
Depending on where it was mined, hematite produced a range of ages, from 660 million years ago to 700 million years ago. That is, they were all formed during the so-called “Great Epoch”. Sturtian Glacierwhich lasted from 715 million years ago to 660 million years ago. At that time, the center of what is now North America was in the equatorial region. The Tabakaiou Sandstone could therefore provide a window into the experience of at least one continent during the most severe global ice ages during the Cryogenian era.
