When the miners began digging, they were chasing after 3 billion year old crystals, but in the process they exposed an entire sequence of geological processes, some of which is beautifully exposed in the sides of the hole.

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The topmost layer is the remnants of processed kimberlite brought out of the hole.

Directly underneath this is the dark red topsoils and alluvial gravels of less than 1 million years in age.

The next light yellowish brown layer is a Basalt intrusion (called a dolerite sill). This layer is made of lavas emplaced during the lead up to the breakup of Gondwanaland and is Jurassic in age or roughly 180 million years old.

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Below are the dark grey shales and tillites of the Dwyka formations which the dolerite was intruded into. This corresponds roughly to the Carboniferous or about 300 million years old. At that time a portion of Gondwanaland was over the south pole and covered by a massive ice sheet. Tillite is the rock that is formed when ice sheets and glaciers melt.

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So it's really interesting to see rocks in a semi-desert, half way to the equator, that were deposited by an ice sheet, at the South Pole.

Below these are the very solid and hard Venterdorp andesite lavas of roughly 2.6 billion years old. You can still see some of the horizontal layering of the original lava flows.

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Below this but hidden by the green alkaline waters are the basement granites which are the oldest of them all.

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Other posts in this series:

The Big Hole. What is the big hole and where is it?
The Big Hole: Part of a greater whole
The Big Hole: Kimberlites, how do they form.
The Big Hole: Diamonds are a girls best friend...
The Big Hole: The other beauty in kimberlites and a wealth of information.
The Big Hole: Information capsules from the deep.
The Big Hole: Setting and Suspension - from busy.org
The Big Hole: digging the hole.
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