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Curator of Micropalaeontology's blog

2 Posts tagged with the susanne_feist-burkhardt tag
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Making a reference collection, taking high quality images of key species, identifying them and publishing the images on the web and in peer reviewed scientific articles are all ways in which expertise can be locked up in the Museum collections. NHM Scientific Associate Tim Potter has been doing just this during his time at the Museum. He studies acritarchs which are an enigmatic group of organic plankton that are present in marine rocks up to 3 billion years old.

 

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Some Lower Palaeozoic acritarch images created by Museum Scientific Associate Tim Potter. In general acritarchs range from about 5 to 200 micro meters.

 

Although we don't know exactly what acritarchs are (the name means unknown origin), they are very important organisms as many are probably primary producers and therefore could be responsible for generating oceanic organic carbon in some of the earliest oceans including the Cambrian Period roughly 500 million years ago. The Cambrian Period was an exciting time for the development of life with many strange organisms arriving and subsequently becoming extinct during the 'Cambrian Explosion' of life. Like many microfossil groups, the acritarchs have potential for dating rocks and subsequently the timing of some of these important events.

 

Acritarchs can also tell us about conditions in some of these ancient oceans; periods of glaciation and major oceanic carbon fluctuations are known to have occurred. Carbon isotopic studies of rocks suggest that the global carbon cycle was disrupted in the late Cambrian about 500 million years ago with increased carbon in the oceans at this time. This is referred to as the SPICE event but the link between this event and acritarch diversity is yet to be proven.

 

Tim studied acritarchs of Cambrian age for his PhD prior to a long career with Shell. After retiring he decided to publish the findings of his thesis and came to the museum to update his identifications using the amazing resources we hold like the John Williams Index of Palaeopalynology. In February, Tim published a key paper on acritarchs with co-authors Susanne Feist-Burkhardt and Museum PhD student Brian Pedder, expanding on work done by Brian for his masters project.

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Tim Potter, Brian Pedder and Susanne Feist-Burkhardt lined up by chance 'in publication name order' in the Welsh Borderland during a collecting trip for acritarchs.

 

Back in 2007, Tim, Susanne, Brian and myself carried out fieldwork specifically to collect samples to fill gaps in the Museum acritarch collections and to support Museum research that was being undertaken at the time. This fieldwork covered classic sites in the Lower Palaeozoic of the Welsh Borderland from the Cambrian to Silurian periods roughly 500-420 million years ago.

 

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Tim Potter collecting a sample from the bottom of a stream near Comley, Shropshire. There are very few exposures of Cambrian rocks in the world and in the UK you have to search hard to find potential sampling sites. This is not an uncommon situation for Lower Palaeozoic fieldwork in the Welsh Borderland!

 

To obtain acritarchs from the rock samples collected, laboratory processing using nasty acids like hydroflouric acid is neccessary. It is not a particularly strong acid but it is deadly as it dissolves pretty much everything apart from the organic constituents of rocks. Splash a bit on yourself and you would not last long! A laboratory with special fume cupboards and much protective clothing is neccessary for processing samples safely. Fortunately for Tim, these samples were expertly prepared by technician Jonah Chitolie.

 

Once processed, the residues were analysed by Tim and single specimens picked out so that they could be mounted and viewed on glass slides. Because the specimens are so small, this is a particularly fiddly technique that requires a lot of patience. Most slides of acritarchs are strew mounts; a small amount of processed organic sample is pressed and cemented between two glass slides using resins like Canada Balsam. For these types of slides, an assemblage is preserved rather than a single indentifable specimen.

 

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Some images of acritarchs from the Museum database.

 

The single grain slides that Tim produced have been photographed and the details and photographs released on the web via our specimen registration system. Tim has been happy with the identifications of most of the Cambrian specimens but would welcome comments on identifications of some of the younger Ordovician and Silurian examples. The Museum database is able to record re-identifications. It is hoped that other experts will log onto this resource and suggest alternative indentifications or back up the published indentifications, further increasing the value of this resource.

 

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The Palaeontology Department on-line specimen database search screen

 

To find these details, log onto our specimen database system and choose 'acritarchs' in the drop down list for 'fossil group' and click the box for 'images only' (as above). Tim is constantly adding more material to the collections so hopefully in the years to come this will develop into a very useful resource for students of acritarchs and help to ensure that important expertise is not lost.

 

Postscript. As I was writing this I was sent details of a PhD studentship on acritarchs based at the University of Lille, France.

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The permanent Dinosaur gallery at the Museum is open every day of the year (except 24 to 26 December) but the recent temporary exhibition 'Age of the Dinosaur' closed last week and now sets off on its travels to another temporary location. Keen eyed visitors to Age of the Dinosaur may have seen some microfossil pictures lurking at the back of the exhibit. Microfossils and dinosaurs are at different ends of the size scale so how can work on microfossils be related to dinosaur research?

 

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The display in the 'Age of the Dinosaur' exhibit including the microfossil images

 

A neat piece of work published in 2008 by several former colleagues in the Journal Cretaceous Research described some ostracods, spores and pollen from a dinosaur excavation site at Ockley in Surrey. These microfossils show that an Iguanodon died and was buried in a temporary freshwater pond, while the spores and pollen indicate that the Iguanodon lived in a world dominated by certain types of ferns and conifers. The microfossil assemblage tells us that the Iguanodon died in the early part of the Barremian, a stage of the Cretaceous 121-127 million years ago.

 

Dinosaur officionados will correct me and say that Iguanodon is now called Mantellisaurus. Details about dinosaurs can be found on the Museum web site if you are interested to read further.

 

In 2001 a large party from the Department of Palaeontology spent two weeks excavating a site at Ockley where the partial skeleton of an Iguanodon had been found by a members of a Geologists' Association field excursion. News of the find had spread very quickly to the popular press so we had to take it in turns to stay overnight in a tent at the site so that we could make sure that is wasn't ravaged by opportunist collectors.

 

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The parts of the Ockley Iguanodon skeleton that were recovered in the excavation.

 

I remember being asked to wield a pick axe and shovel so that we could clear the overlying rock from the rock bed that the fossil bones had been found in. Meanwhile my vertebrate colleagues were on their hands and knees preparing away the bones that had become exposed on the surface. These were then taken back to the museum still encased in the rock so that they could be further prepared by David Gray in the Palaeontology Conservation Unit.

 

My former colleague Susanne Feist-Burhardt collected samples for microfossil study from the dinosaur bed and the beds above and below. These were studied for palynology by MSc student Elly Nye and by David Horne and John Whittaker for ostracod microfossils.

 

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Examples of some of the spores and pollen obtained from the dinosaur site. The palynological record suggests that the dinosaur came to rest on a warm subtropical flood plain surrounded by ferns and conifers.

 

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The freshwater green algae Scenedesmus novilunaris found in the dinosaur bed suggests that its final resting place was a freshwater pond.

 

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The ostracod Cypridea clavata along with other evidence suggests that the pond dried out periodically.

 

Samples close to the dinosaur bed produced the first recognisable ostracods from the Ockley site allowing a firm date of the age of the sediments to be established. The single species of the genus Cypridea found suggests that the pond dried out on a regular basis. The eggs that this group of ostracods produces are resistant to dry periods. As a result, their relatives are often found in modern day temporary ponds. More common Cretaceous ostracods that require permanent water bodies are absent from the Ockley assemblage giving further evidence for the temporary nature of the pond where the Iguanodon came to rest.

 

This was a very interesting project to play a small part in and shows the power of tackling projects as a group. It also shows some excellent potential applications of micropalaeontology so I was very glad that it became part of the 'Age of the Dinosaur' exhibit.



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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