So I’m back in Devon now after the furore that was my student house move and a very busy couple of weeks, in which alas I haven’t been able to post anything much. For that I apologise; however I am back and hopefully more interesting than ever!!! *cue sniggers from the back of the class…*
I live in Devon, very near the border with Dorset… another stange land (like Devon) to which tourists flock every year to gawp at beaches and buildings… but this isn’t what we’re here for today; oh no… today I’m going to twitter on about the urban geology of Lyme Regis… my local (and rather quaint) regency seaside town.
Lyme Regis is perhaps a not unexpected location to find good geological sites, afterall this is the place to which the leading lights of early palaeontology flocked; including Henry De la Beche, Richard Owen, William Buckland and Gideon Mantell amongst others. The Town is also famous for Mary Anning, one of the first in a very long line of fossil collectors who still scour the ledges at low tide to this day.
Lyme may be famous for the Geology on which it is built (I could – and probably will – write several posts on it.) but not alas for the rock from which it is built, though the amount of render/pebbledash around probably provides ample explanation as to why! However there are still some buildings which exhibit the original stones of which they are constucted and some of them contain fossils, creatures frozen in stone for time immemorial – if only people knew what they were looking at!
I took a wander through the town reccently and brought my trusty camera along for the ride, and I’m glad I did because now I can write about some of the beautiful fossils around.
Locality 1: Bench Seat on the folley.
At the eastern end of the towns seafront is what looks for all the world like an 18th century fortified sea wall. You would probably walk through it thinking that something doesn’t look or feel quite right… and you would be correct. It’s not weathered enough, and the reason why is that it is to all intents and purposes a folley, a fake, a forgery! The building was built in 1993 to house a pumping station and water treatment works whilst disguising them sympathetically with the rest of Lyme Regis’ sea front.
There are quite a few good fossils to be found in the limestone brick-work of the sea front here, and the rock appears to be the local Blue Lias limestone, which typically exhibits bivalves both large and small – more on that later. I was drawn more particularly to a bench seat facing out to sea, which showed some beautiful fossils (see right) which at first thought appeared to be some form of coral, though this resemblence was fleeting and almost immediately replaced by another hypothesis – that these are in fact a form of stromatoporid (aka stromatolites), which has since been confirmed (reservedly) by a chat with one of the many friendly palaeontologists of the town.
These fossils are fairly small, being no bigger in the section photographed than three centimetres, but it would certainly make a pretty worktop for one’s kitchen. They have been preserved in lime mud not dissimilar to that in the biomicritic rock I described in my last urban geology post and the density of fossil material was much denser.
In the rock making up the seat back (Portland Stone) I spotted this beautiful internal cast of a relatively large bivalve, at I’ve identified it as Laevitrigonia gibbosa, though as I am neither an authority or particularly good at this identification malarky… I am more than open to being wrong so please feel free to call me on it! (After all, good scientists should be able to admit when they’re wrong!)
Locality 2: Bridge over the River Lym.
Moving along the folley towards the small car park at the bottom of the town, you cross a small bridge across the river that gives the town its name (see below). On each side of the bridge capstones are littered with bivalves and scleractinian (modern) corals. Whilst sadly I cannot identify beyond this level of detail, I have reproduced the photographs below for you to have a look at.
When the rocks that make up the local areas geology (and thus this building stone) were laid down in the Jurassic period, the scleractinian corals were the only members of the coral group still extant. Over the evolutionary history of the coral group, there have been at least eight different branches, but only the Scleractinians survive today, all the other groups including the highly successful Rugose and Tabulate corals were extinct by the permo-triassic boundary (end paleozoic).
I haven’t had a really good look at the make up of these rocks as I foolishly didn’t bring either a hand lens or grain-size card on my little jaunt… however I will add an addendum to this post when I have returned for another look.
I hope you’ve found this interesting, though I realise the solid (non-fossil) geology is somewhat lacking and in need of a re-visit, as always if I have missed something or got anything heinously wrong… let me know!
As for the other two sites I went to… you’ll just have to wait for the next post!
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