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606 Views 1 Reply Last post: Jan 18, 2013 9:48 PM by MikeHardman RSS
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Dec 27, 2012 11:37 AM

fossil of lake bed or sea bed.

Found this piece in a quarry looks and feels like a sea bed. Reminds of when tides gone out at Southport.

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    Jan 18, 2013 9:48 PM (in response to chris)
    Re: fossil of lake bed or sea bed.

    Chris,

     

    It is almost certainly a sedimentary structure, of which there are several broad kinds: they can be found on the top of a bed of sediment (eg. ripples), on the bottom (sole structures formed by scouring or deformation), within a bed (eg. dish structures, grading...), or affecting the bed(s) on a larger scale (eg. offlap, dune bedding). Animals can also create repetitive structures in sediment, which can be enigmatic or can be confused with some structures of non-animal origin (trace fossils).

     

    To be honest, I'm not exactly sure what your photo represents. I would need to examine it in section, and would ideally like to see it in situ to determine which way up it is. Without doing so, I suspect it is basically a set of ripples. Yes: somewhat like what you might find on the beach at Southport, as you put it.

    Ripples are usually asymmetrical, giving a clue to the direction of the water current which helpled them form. Yours are fairly symmetrical and with rounded-off peaks. Such ripples can form where the flow is not consistent, or reverses before it stops. (The flow we're talking about here is probably deeper than that on a beach when the waves are washing up and back.)

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