Lyme Regis’ Urban Palaeontology 2

One month ago I posted Lyme Regis’ Palaeontology 1, in which I talked about two small parts of the Lyme Regis pumping station and waterworks (locations 1 and 2 on the map below) and promised to finish the job with a second post within a fortnight or so… I failed to do so and as such I apologise, but I’m here to right that wrong now.

Satellite map of locations 1 - 4

Locality Map of locations visited on my jaunt... 3 & 4 are discussed in this post!

Ok so with that apology said let us get on with it!

Bench Seating Alcove in Langmoor Gardens

Bench Seating Alcove in Langmoor Gardens

Locality 3: Bench Seat Alcoves in Langmoor & Lister Gardens.

If you stand on the beach or the Cobb (harbour wall) in Lyme Regis and look inland you should see a large grassy park and garden area just above the promenade,  this is Langmoor and Lister Gardens, though the latter name is commonly usurped by younger locals in place of just the former. There’s not a great deal of geology visible in the gardens themselves with one set of exceptions; the alcoves into which the bench seating has been arranged in the gardens.

The alcoves have been “bricked” using local blue lias stone, and as such you can see many small fossils within the rocks although nothing large has been included so we are left looking at very pretty small bivalve fossils. That said a palaeontologist friend of mine has consoled me on many occasions by reminding me that often the most exciting things in the palaeo-world are the smaller things that complete the ecological picture.

Many small bivalves

A death assemblage of small bivalve fossils visible in an alcove "brick"

For example what you can see in the picture on the right is a “death assemblage” (thanatocoenosis) of these small bivalves preserved in a micritic blue lias limestone. You can tell that this is a death assemblage for three reasons (that I observe); firstly the fossils are all disarticulated – the two valves are not connected at the hinge as you would expect in the living organisms, if this had been a “life assemblage” (biocoenosis) you would expect the fossils both to be articulated.

Secondly there is some evidence of winnowing after death – almost all of th valves visible are of a similar size and anything smaller has been transported away, whilst these have been transported away from larger valves.

Finally there appears to be a preferred orientation of the valves in the rock which I will venture to be open side down.

Locality 4: The Cobb.

The Gardens which are the site of locality 3 separates Lyme Regis Town to the north and east from what was historically the Cobb Hamlet, which was a major port until the increasing size of ships and rise of larger ports such as Liverpool spelled doom for the small harbour in the 18th Century. Cobb hamlet is named for the Harbour wall which has seen many versions and has been rebuilt many times in its 1500 year history, with the most recent Cobb being built almost entirely from Portland Stone, the same rock as was used in the construction of the folley/waterworks at the eastern end of the promenade.

Example of a "Portland Screw" (Aptyxiella portlandica) in the wall of The Cobb

Example of a "Portland Screw" (Aptyxiella portlandica) in the wall of The Cobb

There are, as with the rocks used in the folley/waterworks (locaiton 1) many fossils that can be seen in the Cobb, One of the most common fossils that can be seen is that of Aptyxiella portlandica, colloquially known as the “Portland Screw” which is a gastropod (common gastropods are slugs and snails), which can be found in great number and in a variety of orientations in the rock, though only the internal cast tends to have been preserved, with the original shell material having dissolved away during or after lithification – the resulting shape probably giving rise to the common name.

So there you have it, that’s all the locations I visited on the day of my little jaunt into Lyme Regis with my camera, I hope you have found these posts at least interesting, if perhaps not that informative! If you go a-wandering around Lyme Regis looking for some urban geology there are a couple of other good places to go, perhaps you can start at the Post Office where the X-53 bus service drops off eastbound travellers? Either way go and have a look to see what you find!

Ben Brooks

Short-link for this post: http://wp.me/pFUij-5E

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s