A poem based on Rory Mortimore’s exposition on Peacehaven beach (see also Poor Doris): the latest theory on how flint was formed in the Chalk.

If flint could talk from its seams in the Chalk,
Would it expound the great mystery –
How siliceous effusions formed hard, black intrusions
Which mankind has used throughout history?

Academics have proffered some theories, and offered
Explanations of how it occurred.
Rory Mortimore’s speech on the Peacehaven beach
Was spellbinding in every word:

“You can see the flint banding, it’s really outstanding,
But it’s only at certain positions –
That rhythm zodiacal, the Milankovitch cycle,
Periodically sets good conditions.

Chalky pore-water, a silica porter,
Seeps into burrows and cracks.
Then, up from below, an H2S flow
Meets O2 from the sea, and reacts.

That makes a surprising, quite acidic, horizon,
Just perfect for precipitations:
Silica comes out, and the Chalk round about
Gets replaced by flint nodule formations.”

[Photo: discoveringfossils.co.uk]
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