Ageing Something You Find In The Shingle

[Koss1959]

I search Charmouth and Lyme Regis very regularly. All my finds have come from the beach. Just picked up off the shingle. I have been trying to learn more and become a more knowledgeable fossiler so I've been learning the geology of the area.

If I find something in front of Church Cliffs or Black Ven, for example, would it be reasonable to somewhat confidently assume it came from that cliff?

I'm not sure how far things can travel due to long shore drift.

And then going one further, if it did come from that cliff, can you find out what zone it came from? If it's a bone that varies in different species, then you could have an educated guess. But say it was just a vertebra, how do you tell?

Eh, that's a mess. I'll try order the questions...

1. Because something is found in front of a cliff, is it reasonable to assume it came from that cliff?

2. You identify what cliff it came from. Say it was found in a landslip below that cliff. How do you identify what zone it came from? Or can you not?

3. Bonus question: how far can fossils travel due to long shore drift? I guess this is dependent on how calm or stormy the sea is.

Thanks for your help!

[Pumpkinhead]

Look at what the rock is like from the cliff and what the rock is like that you found below it. If both look similar, it is logical to assume that they came from the same place. (In this case, the cliff). As for the other two questions, I'm not actually from the area so I cannot tell you anything specific about that places geology or wave action. My only advice is to find someone who is knowledgeable about the area, preferably a local.

[Auspex]

If you find something at the base of an ocean cliff, there is a better chance that it did not travel far if it still has local matrix adhering and is not water-worn. Even then, it is a supposition based on circumstantial evidence.

Currents can carry things great distances over time.

[NZ_Fossil_Collecta]

Currents can carry things great distances over time.

Baltic amber springs to mind...

[Taogan]

Always be wary of shingle, local councils have been known to move it around for beach defences, but as a rule, if it isn't too worn, if it's fairly heavy and if it fits in with the known geology then a thing hasn't been moved too far. Long shore drift will eventually move fossils, but abrasion would make them unidentifiable fairly quickly, unless, like amber they float.

[Ammojoe]

Good points made so far. As Auspex has mentioned, anything you find ex situ is always a well-educated guess at best. Determining the specific zone of fossils is quite difficult, especially with vertebrate fossils. I think it's impossible to determine precisely which bed an ex situ vertebra (or alike) came from at Charmouth. However, with Ammonites you stand a far better chance of identifying the bed, due to some species of ammonites being index species. This means that a particular ammonite may only occur at a certain horizon within the cliff, and therefore if you can determine the identity of the ammonite (even when ex situ) you can tell what would have been its in situ location.

Another method would be the lithology of the matrix - for example, you can determine some rocks by their appearance and pinpoint the bed that they have come from e.g. woodstones from Lyme Regis.

Short answer is, there's often rarely a foolproof method to precisely locate where an ex situ fossil has originated from.

The other issue I have with worn vertebrae is that there's so much diagnostic information worn away that it becomes immensely difficult to safely identify past Family (Ichthyosauridae). What do you label your specimens as?

Edited June 8, 2014 by Ammojoe

[Koss1959]

From what I've read, the only way you can tell the species of an icthyosaur or plesiosaur is from the skull, scapula or humerus. Maybe a few other bones, I can't remember. But you can't get a positive ID just from the vertebra ex situ.

I don't label my finds. When I get a nice cabinet, I think I will.