The Sea is Not Made of Water by Adam Nicolson

Author:Adam Nicolson
Language: eng
Format: epub
Publisher: HarperCollins Publishers
Published: 2021-05-14T21:05:47+00:00

The lifeless limestones at Rubha an t-Sasunnaich, laid down just after the catastrophe at the end of the Triassic, 200 million years ago.

Life did recover, and the head of the bay, outside the house, is full of evidence for that resilience. The rocks there are the residues of the reoccupied levels, the matrix of the recovery after the ETE crisis was over, when the basalt had ceased to flow, the gases were no longer polluting the atmosphere and the earth had begun its long and slow rebalancing. Over millions of years, the oceans de-acidified and life started again. It was the beginning of one of the great ages, the Jurassic, life remaking itself in a global act of persistence, a return to possibility.

In the 200 million years that have elapsed since then, the level beds in which the mud and limey clays of the new post-Pangea seas were originally laid down have been played with by earth movements and tipped about thirty or forty degrees up from the horizontal. The sea has then cut roughly across them, like a blunt saw through a sheet of marine ply, so that what was once stacked neatly one bed above the other, is now revealed as a low but jagged series of peaks and troughs across the intertidal.

I dug my first pool into one of those troughs. I soon understood that the rocks were making their own signals to me. The layers in them were pulsed, a regular and rhythmic sequence that repeated again and again the same three layers one above the other: a hard grey-blue limestone; a soft lime-rich clay; and some dark, finely laminated black shales. The limestone broke off in chunks if I hit it with a sledgehammer or a pickaxe; I could slice away at the clay which had a consistency somewhere between cheddar and brie; in it were some rounded lumps of iron-rich sandstone, the size of goose eggs, which I could rootle out with one of my wrecking bars like nuts from a cake; and finally the shale shivered off in showers of millimetre flakes when I attacked it with a jemmy.

Slowly I deepened the pool through these layers. Something had happened here which had this rhythm built into it. The geologists are not agreed. It seems clear at least that there was a repeated shallowing and then re-deepening of the sea, a steady flux and reflux across time. The dark black shales are not unlike the worldwide seas of the ETE, the fossilised muds on the dark, fine-grained and anoxic floor of a relatively deep sea in which no life could persist, much like the floor of the Black Sea now. From slightly shallower seas is the grey clay with the egg nodules in it. Those nodules, the scientists agree, are concretions of the iron-rich elements when pressurised by the rock layers above. The last is the hard limestone, which is solid with the fossils of a richly curved and sculpted early oyster called Gryphaea arcuata – the hooked griffin in Linnaean Latin, the Devil’s toenail for the pre-scientific.

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