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Gold Claims For Sale in BC

The Geologic Time Scale for Placer Miners

The Geologic Time Scale divides up the Earth's past on the basis of the age of rocks - particularly sedimentary rocks - sediment deposited in water.

The fundamental principle is called the law of superposition...
In undisturbed layers of sediment, a layer is younger what is under it.

The Time Scale, The Ice Age and Placer Deposits

You can skip directly to the Geologic Time Scale.

The last half-billion years of the Geologic Time Scale is divided into three Eras. The time relevant to placer mining is the most recent Era - the time since the dinosaurs became extinct about 66 million years ago.

This Era is divided on the basis of a large ice age that began 2.6 million years ago. It included multiple Glacial Periods separated by warmer Interglacial Periods - the current Postglacial Period is the latest. For more information, see Ice Age on the Glossary page.

In the latest Era, the time before this ice age began is called the Tertiary Period and the time since then, up to the present day, is called the Quaternary Period. The postglacial part of the Quaternary Period is called the Holocene Epoch.

Almost all placer deposits in BC that are less than a couple of million years old were deposited during the postglacial period or one of the interglacial periods.

During a glacial period, glaciers can rework existing placer deposits. This rarely results in a minable deposits, but exceptions exist where the original deposits were very rich. This apparently happened on Cunningham Creek in the Cariboo.

The Geologic Time Scale

The age ranges are written backwards - more natural for reading the top half of this list from the top down - the part relevant to placer mining.