© Richard Kefford Eorðdraca
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The weather forecast was good. I checked the tides, low at 1245 – perfect. Time for a day out on the Dorset Jurassic Coast.
I checked the gear, food, drink, all packed in the ruck sack. In the car and set off early. Enjoyed the drive through the Autumn Somerset then Dorset countryside. Autumn is well under way. There are early morning low mists on the Levels, cows submerged up to their bodies so they appear to be swimming across the fields. Lines of lingering mists along the rhynes. Leaves dropping in exhaustion from reluctant trees, their strength spent through the Summer in frantic photosynthesis, manufacturing sugars for the fruits of Autumn. Leaves littering the roads.
Turned off the A35 at Chideock, slowly drove down the single track lane to Seatown beach. Rumbled over the wooden bridge into the car park, money taken by the Captain Birdseye look alike who darts out from his shed. He charges by the time you say you are staying so the cost is negotiable…
Boots on, gear in the rucksack, car locked, keys zipped in pocket. Hefted the ruck sack up and then set off over the footbridge, passed the pub on the right and then reached the pebbly beach and set off towards the West, towards Golden Cap which can be well seen from this beach. Every year, the vegetation seems to be covering more of the Cap. There is constant landslipping of the soft rock, shale and mud onto the beach so the first part of the beach has been protected by large rocks placed just under the low cliffs. This also protects the buildings above. These rocks give an additional geological benefit. There are quartz and calcite-filled geodes in the limestones, sheets of calcite dog tooth spar where the rock is faulted. Sigmoid tension gashes appear and there is one that shows evidence of a hot fluid intrusion that has altered the rock each side of the intrusion.
The tide is going out but is still high enough with waves of three feet or so crashing on the shingle with a crash and then the long roar of the drawback as the shingle is pulled once again to the sea after being flung up the beach by the preceding wave. All this crashing of the waves generates a sea fret along the beach giving the impression of a haar but it is not a sea fog caused by a cold sea on a warm day – those are reserved for warm sunny afternoons, this is just a mist caused by the waves.
Belemnites and scallops
There is room to walk, just, between the crashing waves and the base of the cliffs. This gets wider as the tide recedes. Recent cliff falls can be seen, usually accompanied by the trickle of a small stream that released the mud. Impressions can be seen in many places of the ammonites and scallops.
Anoxia ‘death’ horizon
I reach the end of the beach. The way is now blocked by the oozing mud that has fallen over the years. It is moving slowly towards the sea, driven by the small steams that create small gashes and valleys on its surface and the sea that is wearing away the face. It moves very slowly like a glacier. Some areas have been stable enough, long enough for plants to grow.
I stop before the mud as I see that the sea has exposed the belemnite bed, this used to be covered in four feet of shingle a few years ago. One the surface of this bed and for a couple of feet below it are myriads of belemnites that were killed by the anoxic conditions of the time. The anoxia is confirmed by the presence of pyrite nodules that form under these conditions. They will quickly oxidise to destruction if oxygen is present.
Fresh out of the mud
A climb up on to the mud layers, keeping well away from the eroding cliff – falls are common and can often be heard. The soft mud can be treacherous too, and dirty.
A complete and partial ammonite – same species
My luck is in, I find an ammonite. I look it up in my book when I get home Fossils from the Lower Lias of the Dorset Coast from the Palaeontological Association London 2010. Lord and Davis.
Another ammonite on the other side.
It looks like an Androgynoceras capricornus. I intend to clean it up by removing all the mud but, when I start and then turn it over, there is a wonderful surprise and I decide to leave it as it is. Unable to identify the ‘baby.’
Close up of ammonite
A really enjoyable day in a wonderful place.