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The Milestone

The delicate side-tracking operation was handled brilliantly by the team from Geometric Cofor, and we’ve been drilling at full speed again for two days. We’re presently at 1675m, and hope to reach our final depth early next week, all being well.

In the meantime, at 9pm on Thursday 7th of July our drill-bit finally passed the one-mile deep horizon. The stone at one mile down – so our true ‘milestone’ – is a red sandstone. That might not strike you as very odd – lots of sandstones are red where we see them at surface. Think of the beautiful sandstone in the cliffs below the Whin Sill at Bamburgh Castle, for instance: the same red sandstone out of which most of the castle itself is constructed. Normally, though, when we drill into the same sandstones at depth, they are grey. This is because the iron it contains is in the form (‘ferrous’) it adopts in the absence of oxygen. Where sandstones are exposed to the air, they often change to a red colour (the colour of ‘ferric’ iron).

So it is strange to find a sandstone one mile below surface that is obstinately red. What does this mean? Well, it might mean that this sandstone was not accumulated in a river or a swamp, as most of the shallower ones were, but on land, as blown sand in a desert landscape. That would be rare indeed in rocks of the Lower Carboniferous age (350 million years old), which we take this to be.

But red sandstones are also found at depth in the older Devonian rocks (360 to 416 million years old), which are found elsewhere in the UK (you can see these by the river at Jedburgh, for instance). So have we just discovered a previously unknown body of Devonian rocks below the Carboniferous sediments of Tyneside? We can’t tell just now, but maybe some analysis of fossil pollen spores which we are hoping will be done in the coming months will let us know one way or the other.

Filed under: Renewable energy

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Posted on: Jul 8 2011

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