Sunday, 8 August 2010

Where am I?

I'm standing on the bed of a shallow tropical sea, wiggling my toes.  My eyes are closed, yet I can imagine the desert island paradise before me. My head is swathed in a woolly hat to stave off the vicious north wind and the goosepimples on my exposed knees have goosepimples on them.  Where am I?

Northumberland of course - in August. Don't believe the spin the tourist board gives you by the way. The sea temperature off the Northumberland coast is the coldest in the UK.  I'm frozen stiff, enjoying a bracing week's Summer break.  So, what was all that guff about the tropical paradise?  Simple, I'm at Cocklawburn, just south of Berwick upon Tweed, where there are some wonderful geological features including limestone beds laid down when this part of the earth's crust was indeed located in the tropics and millions of creatures living in the warm seas died, fell to the sea bed and are now preserved as fossils in the limestone beds - on which I am standing, wiggling my toes to keep them warm.

The most obvious fossils are the stems of crinoids, sometimes called sea lillies, though they are not plants but animals - echinoderms - related to the star fish and sea-urchins.

The other common fossils found here are brachiopods, filter feeding animals housed in two small shells or valves, and anchored to the bottom or to a suitable substrate.

This part of the coast is one of the best areas in the UK to see exposed successions of carboniferous sedimentary rocks - limestone, sandstone, shale and coal in repeated sequences reflecting the changing climate and sea levels of the period from about 350 to 290 million years ago.  The juxtaposition of limestone and coal fostered the development of an extensive industry in the 18th century. Coal fires were lit in kilns and limestone added. The intense heat broke down the limestone and produced quick-lime which could then be spread onto acidic moorlands and other infertile areas to bring them into commercial agricultural use.

A welcome legacy of the spoilheaps etc around this limekiln is an area of lime-rich soils supporting an interesting and varied plant community.

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