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Limestone

9 March 2014
Geology

This is an interesting observation by Peter Mungo Jupp at www.thunderbolts.info/wp/2014/03/05/the-jurassic-coast-a-transmutation-e… … as in the uniformitarian model limestone is formed slowly, over long periods of time. Limestone rock contains all sorts of fossils – and it is recognised some limestones are actually relic coral reefs. If so this must imply a rapid process – how would you get a fossil reef to fossilise over a long period of time? However, most limestone rocks in the UK exhibit classic layering and do appear to have formed in stages (but not necessarily in a slow and gradual way). Limestone can contain lots of shells, broken or whole, sharks teeth and other oddities such as belamnites, whole of splintered – and can be compared to the chalk. Jupp focuses on the Nautilus shells, a well known feature of the Jurassic coastal cliffs of Dorset. Nautilus also crop up in limestone in many other parts of the UK, inland and coastal. For example, buildings in the town of Buckingham, which is on the River Ouse, have made use of the local outcrops of limestone and it is not unusual to see a nautilus in the wall of an old building. They appear to have been picked out specifically by the builders as a feature, especially on a wall with a street situation. Also, it is not unusual to come across pieces of broken limestone in fields, dragged up by the plough. It is fairly common for such fields to include pieces of limestone with nautillus in them (usually broken as the stones themselves have been subject to repeated bashing by ploughs and farm machinery). Indeed, northern Buckinghamshire and its neighbouring counties are missing much of Tertiary geology. The clay is Jurassic clay, lower down in the sequence of the chalk (which is Crtetaceous in date) and which exists as a scarp edge in the southern half of the county. Something dramatic has removed the geology all the way down to the Jurassic. However, the odd hill or ridge, has apparently survived the 'event' and preserves some of the missing geology. These blobs on the landscape are like  islands in a sea of Jurassic clays. Over the course of history they attracted humans and human settlement, havens from the waterlogging common to the clay country.

Jupp describes the Nautilus of the Jurassic Coast as so common that one is left gasping. How did so many of them come to be fossilised – in an instant as they appear to be preserved with all their soft parts (petrified). His explanation is that electricity was involved – but even if you think in such terms they must all have been buried very quickly, completely overwhelmed by whatever it was that put the lime into the stone.

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