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650 Views 6 Replies Last post: Aug 22, 2014 1:22 PM by Fiona - Museum ID team RSS
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Aug 20, 2014 12:37 PM

Help Identification please Found this fossil at Charmouth last Saturday

I was collecting on the beach at charmouth last Saturday and amonst other gems belemites ammonites etc I found this approx 350 metres West of the visitor centre where there is a land slip.

There is an interesting looking set small bones and what appears to an extreme novice to be a foot or vague outline of a foot like  structure.

I look forward to your thoughts.

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  • Hello Rock-troll,

     

    These are what we call trace fossils burrows.

     

    What is a trace? Traces are all around us, for example, footprints made during a walk on a sandy beach, small holes in shells caused by boring animals, or holes in leaves made by insects.

     

    Trace Fossils. Trace fossils may be trails, tracks and trackways, burrows and borings. They are the evidence of biological activity 'frozen' in time as the result of an organism doing something and then moving on.

     

    "Burrows are invasions of unlithified sediiment by diggers, sediment compactors and sediment ingestors. Borers are cutters, grinders and dissovers of hard substrates, such as shells, wood and limestones. Some are predators or parasites, whereas others are inhabiting a protedted environment (after Donovan & Fearnhead, Deposits, 39, p. 38 - 39).

     

    Lithify = "transform (a sediment or other material) into stone".

    Sediment = "Matter that settles to the bottom of a liquid; dregs".

    http://www.oxforddictionaries.com/us/definition/american_english

     

    I hope this has been of interest to you.

    Fiona

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      • Hi Rock-troll,

         

        Glad to hear this has been interesting to you.

         

        The small, branching asymmetrical and smooth-walled burrow systems in your photograph appear to be different sized diameter examples of Chondrites. Size ranges (1mm and 2.5 - 3.5 mm). Widespread, Dorset Lower Lias ichnotaxon, regarded as highly tolerant of low oxygen levels. More information can be found in the book:

         

        • Fossils from the Lower Lias of the Dorset Coast, (Chapter 6. TRACE FOSSILS by Christopher Paul and Charlie Underwood),  Palaeontological Association Field Guides to Fossils: Number 13, published by the Palaeontological Association, Londo, 2010.

         

        We have books in the Angela Marmont Centre and you are more than happy to pop in and read or browse.

         

        The larger, complex branching, more or less cylindrical horizontal burrow is probaly Thalassinoides. These burrows are Y shaped are almost always reworked by Chondrites and commonly found in limestone and pale marl beds of the Blue Lias Formation and Black Ven Mudstone of Charmouth.

         

        The study of trace fossils = ichnology; that of modern traces = neoichnology. Trace fossils are named in a system that looks like the Latinised binimial system of Linnaeus, but is separate because trace fossils are sedimentary structure made by organisms and not the remains of organisms as such.It is rare to find the  trackmaker at the end of the track, however, an example of the world's longest death track was discovered in 2002 - a 9.7m -long trackway (ichnofossil) with its tracemaker, a horseshoe crab at the end of it.

         

        Sorry, it is coincidence that one looks like a small wing bone.

        Fiona

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          • Hello Waldo,

             

            Yes, actual burrows made by animals. Sadly, it is usually, not possible to identify the animal that made the burrow trace fossil unless the animal is preserved at the end of the burrow! This kind of evidence is very rare. Like Sherlock Holmes, detective work is required, considering all the available evidence, such as:

            • shape
            • size
            • texture

             

            The Horse shoe crab is a rare example of an animal found at the end of its trace and therefore we see a 'window' into the animals last few moments of life, but this is extremely unusual.

             

            Burrows may provide hints about what kind of animals could have made the burrow, not the definitive answer. Each clue adds to the jigsaw and this is part of the excitement of discovery and problem-solving! Sometimes, it is many years until enough pieces of the jigsaw solve the mystery. This is why one of the reasons fossil collecting is such fun .....  the next specimen you find might have some new information to science (if you have all the locality information with the specimen).

             

            What information can burrows give us?

             

            1. Clues about the consistency of the substrate at the time they were made.
            2. Burrows take us into the land of the digger, providing clues about what the environment was like.
            3. The behaviour of the animal that made them.
            4. The presence of burrows means there must have been enought oxygen for life as least some of the time.
            5. Burrows usually have a circular cross-shape, so if the fossil is ellipse-shaped, it is evidence it has been squashed and that the sediment had undergone compression.

             

            What do your fossil burrows indication from the photo?


            Lower Lias fossils like yours are predominantly burrows that were excavated in soft sediment. Burrows are made into unlithified sediment, forcing the grains aside; lithification comes later. If sediment shows evidence of burrowing, it is evidence that the oxygen levels were high enought to support life at least some of the time.

             

            Ammonites.  I suspect you should leave the ammonites alone and enjoy them as they are. If the surrounding rock is soft you could try using a dental probe very slowly and carefully to remove soft sediment, keeping the sharp point away from the fossil and only very small movements. Preparation of fossils requires great care and patience - this is not my field of specialisation.

             

            I hope this has been helpful, I am sorry that the terminology is complicated and hope that I have answered your questions satisfactorily.

             

            Remember to label your fossils with the locality data,

            Fiona

             

            Specimen name:

             

            ………….................................

            Age:

             

            Locality: 

             

             

            Collected by:

             

            Date:

             

             

            Message was edited by: Fiona - Museum ID team

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    • (minor point: sediment definition inaccurate: should be 'fluid' rather than 'liquid' (fluid = gas or liquid) - since sediment can form by deposition from the air as well)

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