The Durham coast isn’t a top destination for fossil hunters, who find richer pickings further south under the crumbling cliffs around Whitby, but occasionally interesting fossils do turn up on our beaches. I found one has week, on Blast beach just south of Seaham, which gave a tantalising glimpse of how the landscape might have looked three hundred million years ago.
Blast beach was formerly a site for dumping colliery waste but in recent years the magnificent Turning the Tide project has made great strides in restoring this coastline to its former, pre-industrial glory. There are still large boulders on the beach that were transported with colliery debris and it was when I split one of these that I found the remains of a plant that had been embedded in the rock for three hundred million years. The compressed, jointed stems, now turned to stone, belonged to a giant horsetail.If you double-click for a larger image you can see that there are two reasonably intact compressed fossil stems here - one running at an 11 'o'clock to five o'clock angle and the other running eight o'clock to two o'clock.
Back in the Carboniferous, when the coal measures and the land mass that is now Britain was nearer the equator, these strange plants formed tropical, forests in swamps that would have been home to early amphibians and giant dragonflies.
Horsestails still exist today, as 'living fossils', but are a pale shadow of their extinct ancestors. Gardeners are familiar with the field horsetail, which is a troublesome weed but only grows about a foot tall. Today specimens of the great horsetail, the largest horsetail species that grows in damp places along this coast, reach a height of about five feet. Judging by the width of the fragment of fossil stem that I found, this long-extinct plant must have been at least four times as tall. Larger fossils that have been found indicate that these ancient plants sometimes grew to a height of sixty feet or more.