There are two common questions by beginners and enthusiasts: “I’m new to fossil collecting, where can I collect?” and “I’ve found a fossil, what is it?”
I’m blessed with owning SS Buckman’s Type Ammonites – six whole volumes of pictures of some of the most famous ammonites found, along with their names, but sadly, only the briefest of descriptions of where they were found.
“Dactylioceras semicelatum, (Simpson) Tenuicostatum Zone, near Whitby.”
How, given that simple line of information, can I go out and find one of these fossils and then, assuming I find one, how can I identify any other specimens I might be fortunate enough to find with it?
The following account applies regardless of your particular area of interest, be it Jurassic ammonites, Carboniferous trilobites or London Clay sharks’ teeth.
What is needed is the realisation that fossil collecting must be only the hard physical result of a much deeper interest and passion for geology, palaeontology or the earth sciences in general, otherwise, it is nothing more than collecting pretty stones. With a deepening understanding, one should be able to read the stratigraphy, the specimens and the geological accounts like a good murder novel and solve the crime by collecting all the clues. Then, you can rejoice in knowing that you have learned just a little more about our great hobby.
Most of the clues will come from books, but not the big glossy picture books that skim over such a wide range of orders of fossils, but with little or no depth – what you need are dull looking wordy books, with few pictures, but really useful information in the text. The starting point will be the three volumes published by the Natural History Museum – British Caenozoic Fossils, British Mesozoic Fossils and British Palaeozoic Fossils. Each of these give line drawings of the most frequently found species of each group or order of fossils, over the three great divisions of time that life has existed on earth. My species (Home sapiens) is not in the middle book, which covers the Jurassic era, but there is a Dactylioceras tenuicostatum, and Buckman’s description says Tenuicostatum Zone, so here is my first clue – the index specie or zone specie is D. tenuicostatum.
The most useful part of these books are not the pictures, but the information given in the first few pages – a map showing all the Jurassic in Britain, stratigraphical tables and geological time scales. All go together to help put the clues into context – in this way, my specimen is placed in the zone found in the Grey Shales in the Whitby area.
So what clues have we so far?
Dactylioceras or D. semicelatum is found in the Tenuicostatum Zone, which is named after D. Tenuicostatum, which is the Index specie and can be found in the Grey Shales, near Whitby in North Yorkshire. Time for more books…
British Regional Geology
Now, these are really useful field books, with the whole of the British Isles split up into 20 sections and crammed with information. So, wherever you live, there is a Regional Geology volume specifically covering your area. I must get the rest of the information from here. This book has lots of maps, ‘sections’ and diagrams showing the stratigraphy or strata that I will find, and locality maps and well written information about what to find when I get to the beach, together with photographs. I can now see that the Grey Shales lie below the Alum Shales, and are exposed at a number of locations along the North Yorkshire coast. It even tells me the best access points and, possibly most importantly, that the Tenuicostatum Zone is actually split into four smaller ‘sub-zones’, and each of these sub-zones has a representative fossil species. However, this is not quite enough information to do a 1,000km round trip for my search.
Dactylioceras semicelatum is found in the Grey Shales and is represented by the Tenuicostatum Zone, which is split into four sub-zones, of which semicelatum is the highest one. So, if I find the specie shown in my first book choice, I know that my specimen should turn up a little higher in the cliff. Time for more books…
The Natural History Museum website includes a really good book section and, checking through that, I find a special paper written by MK Howarth, The Stratigraphy and Ammonite Fauna of the Upper Lias Grey Shales of the Yorkshire Coast. It is out of print and unavailable at the library, but photocopies are available, and you get to keep them. Perfect – all the stratigraphy, localities, full details on the subdivision of the zone, correlation with other areas, full descriptions of not just the specie I’m after, but of all the species in the shales, and most important, pictures showing the variability of each species.
So, the case for justifying the round trip is that, to find my specimen, I know the geographical area to look at and the strata I need to look in. Thanks to the last book, I know which actual bed to look in and that it lies 10m above the most prominent visual marker in the cliff. I also know that each specimen is found in a nodule and a fairly precise shaped nodule at that. I know how far to walk along the beach, and I have the tide tables so I know I won’t get cut off by high tide. I have pictures showing the various beaches and the various species I can expect to find. What more can I need?
So, I’ve gone from a very general book with little information, through a more specific book with more information, to a very precise paper giving every bit of information I could want, right down to grid references. This process applies whatever the area of geology. Others, with far more brain cells than me, have done all the hard work and they have put all that effort into writing books and papers for the only possible reason – that is, to share it. So, if you want a trilobite from North Wales, a shark’s tooth from Sheppey or an ammonite from the Isle of Skye, can I suggest you read a good book first?
Oh yes, I did the round trip and found more than a dozen different types of ammonites including six very nice Dactylioceras semicelatum.
Neil Lovesey