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Curator of Micropalaeontology's blog

2 Posts tagged with the pollen tag
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On 13 Feb a new temporary exhibition opened here at the Museum entitled Britain: one million years of the human story. It includes some images of microfossils from our collection in the display.

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Scanning electron microscope (SEM) images of pollen grains from our collection that appear in the exhibition.

 

These and other microfossil collections housed behind the scenes help with dating the finds, reconstructing the environment, landscape and climate of these first human settlements in Britain and provide the climatic context for the recent discovery of the earliest human footprints in Britain on a Norfolk beach.

 

The AHOB Project and micropalaeontology

 

The exhibition highlights the work of the Ancient Human Occupation of Britain (AHOB) Project and its predecessor projects. The current project, funded by Calleva, is investigating the timing and nature of human occupation of the British Isles, the technology they used, their behaviour, the environment they lived in and the fauna sharing the landscape. The microfaunas and floras mentioned here were recovered by project researcher Mark Lewis and project associate member John Whittaker.

 

Mark is a palynologist and has used the distribution of pollen grains in the sediments surrounding the human finds to interpret ancient climates and landscapes. Pollen grains that range in size from 10-100 microns can be found in sediments millions of years after the plants that produced them have died and decayed.

 

The Museum collections

 

Mark regularly uses our collection of modern pollen and spores to interpret the pollen floras that he recovers as part of the AHOB Project. We recently transferred this collection from the Botany Department and the images in the exhibition were taken from the collection of SEM prints and negatives that accompanies that collection.

 

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Part of our modern pollen collection. Slides are housed in special plastic sleeves and arranged by plant family name.

 

John Whittaker spent his entire career as a researcher here at the Museum and is a now a Scientific Associate in the Earth Sciences Department as well as being an Associate Member of the AHOB Project. In a previous blog post I highlighted his microfossil finds from three key early human sites at Boxgrove about 500,000 years old, Pakefield about 700,000 years old and Happisburgh (prounced Haze-boro) about 900,000 years old. Many of John Whittaker's microfossil slides are deposited here at the Museum.

 

Ancient landscapes

 

The pollen grain illustrations from the exhibition were chosen because of their use and importance in reconstructing ancient environments, particularly the vegetation dominating the landscapes in which the ancient humans lived. The scanning electron microscope images shown above from left to right are:

 

1. Dandelion-type e.g. Taraxacum - this herb indicates dry grassland or disturbed open ground

2. Dwarf willow, Salix herbacea - characteristic of rocky, open ground as found during cold periods

3. Montpellier maple, Acer monspessulanum - currently native to the Mediterranean and central Europe, this tree was present in Britain only during the last (Ipswichian) interglacial about 125,000 years ago

4. Bogbean, Menyanthes trifoliata - shallow water inhabitant of bogs and fens during both temperate and cold periods

5. Common valerian, Valeriana officinalis - herb indicating either dry or damp grassland as well as rough ground

 

Environments of deposition of sediments


Ostracods and Foraminifera collected by John Whittaker from Boxgrove indicate a marine raised beach and a later terrestrial deposit with freshwater ponds below chalk cliffs.

 

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The saltmarsh foraminiferal species Jadammina macrescens has been recovered from Happisburgh and is consistent with interpretations that the site is situated near the mouth of the ancient large river, possibly the River Thames.

 

070314-2.jpgThe foraminiferal species Jadammina macrescens is common in saltmarsh environments.

 

The microfossils were able to show that the Slindon Sands were deposited in a wholly marine high-energy environment, whereas the Slindon Silts were deposited in a shallow intertidal environment at the margin of a regressive sea. This sort of information is vital when interpreting the archaeological finds from the site.

 

Ancient climates

 

River sediments containing flint artefacts have been found on the coast of East Anglia at Pakefield. The oldest artefacts came from the upper levels of estuarine silts where both marine and brackish ostracods and foraminifera have been recovered.

 

070314-1.JPGReconstruction of a scene at Happisburgh about 900,000 years ago by John Sibbick. (copyright AHOB/John Sibbick)

 

Other evidence from mammal, beetle and plant remains suggests a setting on the floodplain of a slow flowing river where marshy areas were common. The river sediments were deposited during a previously unrecognised warm stage (interglacial) and the presence of several warmth loving plants and animals suggests that the climate was similar to that in present day southern Europe.

 

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Pollen and mammal fossils recovered from Happisburgh suggest that the climate was similar to that of southern Sweden and Norway of today with extensive conifer forest and grasslands. The floodplains were roamed by herds of mammoth and horses. Foraminifera such as the species Ammonia batavus are characteristic of warmer climates.

 

Evidence of reworking of some sediments

 

The interglacial sediments at Pakefield are overlain by a thick sequence of glacial deposits which include till and outwash sands and gravels. These contain reworked (Cretaceous and Neogene) microfossils transported from the North Sea Basin by glaciers. This is important information as fossils found in these redeposited sediments could be give false indications as to the climatic setting and dating of any finds.

 

Dating deposits

 

The dating of the deposit at Happisburgh is provided by a combination of mammoth, horse, beetle and vole finds as well as the Middle Pleistocene ostracod Scordiscia marinae. Work by John Whittaker and the AHOB team at a number of other Pleistocene sites across the SE of Britain has increased the potential of ostracods as tools for dating these sediments.

 

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The extinct freshwater ostracod Scordiscia marinae has been found at both Pakefield and Boxgrove and is

characteristic of the Middle Pleistocene period. An example of a microfossil that is useful for dating sediments.

 

Earliest footprints

 

A flint handaxe recovered from sediments recently exposed on the foreshore at Happisburgh provides part of the evidence for the earliest human occupation of Britain. Several other Palaeolithic sites have since been discovered there including sets of early human footprints on the foreshore that made the national news at the time of the opening of the exhibition.


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A Palaeogeographic map of Britain the in Early Pleistocene showing the land bridge between Europe and the position of the Thames and Bytham rivers. (Courtesy of Simon Parfitt and the AHOB Project)

 

Pinus-Picea HSB_blog.jpgPine (Pinus) and spruce (Picea) pollen recovered by Mark Lewis from the sediments that preserved the Happisburgh footprints.

 

Pollen analysis of the sediments adjoining the footprints revealed the local vegetation consisted of an open coniferous forest of pine (Pinus), spruce (Picea), with some birch (Betula). There were some wetter areas where Alder (Alnus) was growing; patches of heath and grassland were also present. These all indicate a cooler climate typical of the beginning or the end of an interglacial recognised at other Happisburgh sites.

 

Come and see the exhibition

 

I would recommend that you come and see the exhibition Britain: one million years of the human story if you can, before it closes at the end of September. If you can't then there are a wealth of interesting items on the Museum website including a video showing the recently discovered footprints.

 

Quite rightly the artefacts and larger fossil materials collected from these early human sites in Britain dominate the exhibition along with the amazing life-sized models like 'Ned the Neanderthal'. Hopefully this post has shown that there are many other undisplayed collections held behind the scenes here at the Museum that are just as important in telling us how, when and where the earliest humans lived in Britain.

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In January we transferred the Botany Palynology (pollen and spore) Collection to a new location within the micropalaeontology collections. The  collection includes 32,500 glass microscope slides and 155 files of images of pollen and spores from named living plants from worldwide locations. So why should we be interested in moving this collection to the Palaeontology Department?

 

This collection is already being used by Earth Science staff studying the contents of fossil hyena dung, evidence of early human agricultural activity and changes in the landscape over approximately the last 2.5 million years as a result of climate change. The collection also has potential for supporting forensic studies to help solve crime.

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Dr Tom Hill taking great pride in wheeling a trolley of pollen and spore slide cabinets past the giant Sequoia in the main hall of the museum. For health and safety reasons we were only able to move the collection before the Museum opened to the public.


 

In one of my first blog posts - what is micropalaeontology? - I mentioned that there is not always a clear distinction between fossil and extant (living) collections and this is very much the case here. This is an important collection for palynologists looking to reconstruct environments over the the Quaternary Period which covers approximately the last 2.5 million years as many of the plant species present today are represented in the Quaternary fossil record.

 

Pollen and spore grains have an outer wall of an extremely resistant material known as sporopollenin so are widespread in both fossil and recent terrestrial and near shore sediments. Most are smaller than 50 microns so relatively small samples can produce thousands of pollen grains of species diagnostic of particular climatic conditions.

 

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Some of Tom's Holocene core from Somerset, showing a lighter estuarine layer between freshwater peats.

 

Dr Tom Hill of the Earth Sciences Department at the Museum is analysing pollen from sediments from Somerset that cover the Holocene Epoch (i.e. the last 11,500 years).  He collected them using a sedimentary corer, which is essentially a larger version of an apple corer that is inserted into the ground to extract deposits preserved beneath our feet. He said, 'by taking sediment samples at regular intervals throughout the sediment sequence, you are able to develop ‘snapshots’ of what the landscape looked like every few hundred years.'

 

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Tom doing fieldwork with a sediment corer in a 'real field' at Shapwick Heath Nature Reserve.

 

The landscape changed in response to climate and human activity: an abundance of tree pollen suggests that woodlands dominated the landscape while shrubs, herbs and grasses infer an open grassland setting. 'Shifts from woodlands to grasslands are often indicators of human activity in the form of deforestation; the earliest cereal pollen found in these deposits is an indicator of the onset of agriculture during the Holocene' according to Tom.


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Hordeum secalinum - barley, BM10490. Cereal crop pollen grains like these are much larger than average (>40 microns), are typically round with a single opening (pore) and indicate periods of cultivation during prehistory. Photo Tom Hill.

 

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Artemisia - mugwort, BM8975_1. This species/genus thrives on bare ground with immature soil and is often found in sediments accumulated during cold periods such as late glacial episodes in the Earth's history. Photo Tom Hill.

 

Mark Lewis of the Ancient Human Occupation of Britain (AHOB) Project has been using the distribution of pollen from sediments and hyena coprolites (fossil dung), to reconstruct Quaternary environments. Coprolite pollen is useful in situations where sedimentary pollen is absent, for example in caves, where evidence of early humans is sometimes found. Pollen grains can occasionally be reworked from older sediments so analysis of coprolites alongside sediments associated with early human finds can be a useful test to see if the pollen has been preserved in situ.

 

Mark worked on pollen assemblages from Happisburgh, where the earliest evidence of human activity in Britain has been uncovered from c.850,000 year old sediments (for details of their publication in Nature see my previous post on what microfossils tell us about the early humans in Britain). These pollen assemblages showed the climatic setting of the finds and led to breakthroughs in the understanding of early human behaviour, adaptation and survival.

 

Both Mark and Tom are actively using this collection for their research by checking identifications of plant species represented by pollen in their samples. Catalogues, including 8 volumes published by the Northwest European Pollen Flora Project, provide 2-dimensional reference images of pollen but there is no substitute for examining museum reference collections like this one under a microscope. 'The collection provides the user the opportunity to look at numerous examples of an individual species present on a single slide, and review that species in multiple orientations' said Mark Lewis.

 

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Micropalaeontologists/palynologists Steve Stukins and Tom Hill examining the Northwest European part of the pollen and spore collection in its new home in the Palaeontology Building of the Earth Science Department.

 

The Northwest European part of this collection is particularly well ordered thanks to Dr Peter Stafford, Palynologist at the Museum until his death in 2009 who was a major contributor to the collection and publication of the Northwest European Pollen Flora volumes. He worked with many palynologists including Mark Lewis and Prof Steve Blackmoor, former Keeper of the Botany Department. As a result it is now possible to locate examples of the pollen and spores of a named Northwest European plant with ease.

 

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Tom in the old Botany tower examining some of the 155 folders of scanning electron microscope images of pollen and spores prior to their transfer to the Palaeontology Building.

 

The remainder of the 32,500 glass slide collection is currently housed in old metal drawers that do not conform to current storage standards and will need to be transferred into a cabinet next to the Northwest European collection. A start has been made by volunteers and students to rehouse the slides in special conservation grade sleeves but there is much work remaining to be done.

 

While I am very glad that this collection has been moved to our department, it would take me the rest of my career to carry out this task alongside the other collections management responsibilities that I have. As a result Tom Hill will shortly be advertising a couple of volunteer opportunities to help re-arrange the remaining part of this important collection.

 

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Slides of pollen from cannabis plants housed in special conservation sleeves in the Northwest European Collection.

 

Finding slides from cannabis plants jogged my memory to mention that while we anticipate that Quaternary palynologists will be the main users of the collection, there are applications for this collection beyond Palaeontology. Pollen grains present in mud on shoes or in tyre treads have been used to link suspects to crime scenes. This collection has potential to act as a reference for forensic palynologists as well as those looking to study the Quaternary.

 

Finally a big thank you to Tom Hill, Steve Stukins and Jo Wilbraham for help with transferring this important collection from Life to Earth Sciences and to Mark Lewis for providing details of the history of the collection and his research. The collection is available to - and will hopefully continue to be used by - both Life and Earth Scientists.



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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