Visit the East Lothian coast to walk a limestone pavement, discover fossil coral reefs, rooted soils, worm burrows, and a volcanic cone
This short coastal walk along the shore from White Sands Car Park to the Barns Ness lighthouse follows arguably the best exposures of limestones in east central Scotland. Though limestone is dominant, you can also see other sedimentary rocks, including sandstone, mudstone and a thin coal seam. This is an ideal place to see lots of fossils and collect from loose material.
The rocks are about 320 million years old (from the Carboniferous Period) and were laid down as soft sediment when Scotland was located just south of the Equator, and the climate was tropical, both hot and wet. Sea levels kept rising and falling, so that at times this area was under shallow seas, and at others it was a flat coastal plain. The sea level changes were caused by subsidence of this area, sediment compaction and changing global sea-levels due to an ancient ice age. The abundant colonial corals in one of the limestones indicate that they lived in tropical, clear seawater. However, rivers were also flowing down from the mountains to the north; they brought mud and sand, which silted up the shallow sea and reclaimed the land, producing muddy coastal swamps and deltas with low-lying sandbanks and river channels. Eventually this new land was colonised by lycopod forests (similar to mangrove swamps today), which were later drowned by the ongoing cycle of land subsidence and sea-level rise.
Barns Ness is a great place to find fossils; you can see body fossils – the remains of the actual animal or plant, and trace fossils which are the remains of the burrows or trails left by an animal. Body fossils to find are: colonial coral (Siphonodendron), solitary coral (Koninckophyllum) and many other shells and crinoid discs. Trace fossils are the burrows: Zoophycos, Thalassinoides and Rhizocorallium. The lycopod forests have left a series of ‘potholes’, where the trunks once stood, which can be seen when the tide is low.
Barns Ness is also a good place to appreciate the agricultural and economic importance of limestone in the past and present. The lime kiln at the back of the beach was one of many in the area where layers of coal and limestone were burnt to create quick lime for agriculture. This was a dangerous and labour-intensive process, but proved its worth in increased crop yields. Slabs of the Koninckophyllum-rich limestone was produced as decorative marble. In the distance beyond the active quarry stands the tower and chimney of Dunbar Cement works, which processes the local limestone to produce cement. This is the only cement works in Scotland, producing one million tonnes of cement a year.
Since Dunbar is so close, the cliff top walk there is a rewarding addition to a Barns Ness visit and an opportunity to see a contrasting coastline. The cliffs are mostly composed of 345 million-year-old red volcanic ash. Imagine the scene when local volcanoes were erupting, the sky would have been choked with black ash and gas, with blocks of rock flying through the air.. At the far west end, accessible exposures on the beach show the beds of ash in close-up; you can also see an extensive wave-cut platform, an archway, caves and sea stacks. Around Dunbar Castle and the Battery you will find harder lumps of igneous rock from inside one of the volcanic craters.
Text contributed by Mike Browne
Find out more:
Download Barns Ness and Dunbar leaflets from http://www.edinburghgeolsoc.org/publications/geoconservation-leaflets/
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