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Curator of Micropalaeontology's blog

2 Posts tagged with the nannofossils tag
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It feels strange recommending readers to go to another museum. However, this is a great example of the application of Micropalaeontology to archaeological studies and the use of our nannofossil collection. My colleague Tom Hill has just returned from a meeting on 'Geological applications in Archaeology' so this subject is receiving a lot of interest at the moment.

 

Just before Christmas I had an enquiry from the British Museum asking me to provide a high definition image of a nannofossil for their multimedia gallery guides. The image was taken by my former colleague Jeremy Young as part of research on the Folkton Drums published in the journal Antiquity in 2004 with British Museum staff Andrew Middleton and Janet Ambers.

 

The Folkton Drums

 

These carved stone cylinders known as the Folkton Drums were found associated with a child's burial site at Folkton near Filey northeast Yorkshire. The diameter of the largest is 146mm and they are made of incised stone with a grooved ware pottery design indicating a probable Later Neolithic age of about 2,500-2,000 BC.

 

Folkton_Drums_AN00155870_001_blog.jpgThe Folkton Drums. Image copyright: The Trustees of the British Museum, ref AN155870001, registration number 1893,1228.15.

 

Nannofossils and the museum collection

 

Jeremy Young was asked to analyse a very small amount of material removed from a blemish on the bottom of the smallest item. At the time it was not known if the stone was chalk or magnesian limestone. Chalk contains the remains of tiny calcareous coccolith plates formed by a unicellular plant called a coccolithophore. These are present in the oceans of today and are widely used for studies on recent changes to our oceans and environment.

 

The Museum houses a large collection of fossil and recent coccolith preparations, and images made by Jeremy Young. Because most coccoliths are less than a thousandth of a millimetre in size, it is very difficult to isolate them as individual specimens or to find the same specimen again even using a scanning electron microscope. As a result, images are just as important as the preparations from which the images were made and species are often defined by images alone. We have a collection of tens of thousands of such images.

 

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A  false coloured scanning electron microscope image of the fragment of Folkton Drum analysed by Jeremy Young.
The scale bar is 10 microns which is 0.01 mm.

 

What the nannofossils told us?

 

The fragment contained a typical late Cretaceous coccolith assemblage dominated by Watznaueria barnesae, Biscutum constans and Prediscosphaera cretacea. The species Micula staurophora suggests a Coniacean-Masstrichtian age of the Cretaceous (c. 65-85 Mya). The coccolith evidence suggests that the drums were made from deposits of the Upper Chalk rather than Magnesian Limestone.

 

Chalk is available locally and Magnesian Limestone from deposits about 45kms away. However, the results cannot show for certain that the chalk used was derived locally as the outcrop of the Upper Chalk Formation covers a large area of England. A non-destructive method called Raman Spectroscopy used by Janet Ambers at the British Museum also confirmed a chalk rather than Magnesian Limestone composition.

 

Where to see them?

 

The Folkton Drums can been seen in Gallery 51 at the British Museum. The nannofossil image is shown as part of the British Museum multimedia guide available in 11 different languages on request. If you are interested in the subject of 'Geological applications in Archaeology' then further details can be found via the University of Leicester web site.

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What is micropalaeontology?

Posted by Giles Miller Jun 21, 2011

The answer to this question is the straightforward part of this post: palaeontology is the study of fossils and micropalaeontolgy is the study of microfossils. Alas, that’s the easy bit done… what then, are microfossils?

 

I’ll assume that we all know what a fossil is (if not, I recommend starting here) so a microfossil must be a small fossil, right? Actually, this is a harder question to answer than you might think so here are some thoughts on how large a microfossil is, how old they are and how we manage them at the Museum.


Size

There is no agreed size below which a fossil stops being a large fossil and starts becoming a microfossil. Some people arbitrarily say that if you need to use a microscope to view a fossil then you are looking at a microfossil. However, some fossils we consider microfossils measure more than a couple of centimetres in diameter. The rocks that were used to construct the pyramids in Egypt contain microfossils that can be as large as a ten pence piece!


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Photo of Egyptian pyramid courtesy of Bobbie Molloy.


This size delimiting definition also gets slightly difficult to use when you are studying the microscopic parts of a larger organism, for example the fossilised scales of a fish or a minute example of something that is usually larger like a gastropod (e.g. a snail). Most people studying these topics would consider themselves microvertebrate workers or gastropod workers and not micropalaeontologists. However, many micropalaeontologists, like me also study microscopic remains of larger organisms like fish that they find during laboratory preparations for other microscopic remains.


Biological classification

Some people try to restrict micropalaeontology to particular biological groups that are commonly considered microfossils. This can also be open to personal opinion, for example, palynologists study microscopic organic remains like spores, pollen and oceanic plankton – all microscopic in size – but some of them would consider themselves palynologists rather than micropalaeontologists. The Micropalaeontological Society defines its specialist groups to reflect biological classifications of organisms commonly accepted as microfossil groups.


Age

As with size, there is no agreed age beyond which something stops being recently dead and becomes a fossil. With specimens in this narrow window of age (ie 0-10,000 years old) it is virtually impossible to tell how old a microfossil specimen is without carrying out some sort of destructive chemical analysis on it.


Our collections

At the Museum, we mainly follow the Micropalaeontological Society's definition of a microfossil and in the Palaeontology Department we have collections of Foraminifera, Ostracoda, conodonts, Radiolaria, nannofossils and various palynological groups such as the dinoflagellates and spores. In future posts I will introduce each of these microfossil groups as I highlight projects that are currently happening here at the Museum.


My job is to manage all of these collections which number over 750,000 objects. It would be impossible to count the exact number of specimens because some slides and residues contain hundreds of thousands of specimens.


The lack of clarity over what age makes a microfossil causes problems sometimes with deciding where to store specimens in the Museum collections. In the Palaeontology Department we have all the extant (modern) Foraminifera as well as the fossil specimens, so no problem there. However, ostracods are split between our department and the Zoology Department, with us holding the fossils and Zoology the recent (extant) forms. In practise it is very difficult to draw the line between fossil and recent and we certainly have some ostracods that could be in the Zoology Department and probably vice versa.


The majority of the microfossil collections are Foraminifera, which are unicellular animals with a foramen (i.e. an opening, sometimes multiple) that form small shells of calcium carbonate, silica or organic materials. Examples of Foraminifera are shown below, where the field of view of the slide from the Heron-Allen Collection is about 2cm.


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The Heron-Allen Collection

 

I mentioned that some micropalaeontologists like me also work on microscopic fragments of fish (microvertebrates). At the Museum these are kept with the fish collections so they do not come under my ‘jurisdiction’. However, I still study them and some of my most important discoveries have been on this subject as you will find out in the next post to the blog.



Giles Miller

Giles Miller

Member since: Apr 21, 2010

This is Giles Miller's Curator of Micropalaeontology blog. I make the Museum micropalaeontology collections available to visitors from all over the world, publish articles on the collections, give public talks and occasionally make collections myself.

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