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3 Posts tagged with the micropalaeontology tag
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Palaeoenvironmental analysis of a Mesolithic-Neolithic sedimentary sequence from Queens Sedgemoor, Somerset

 

Dr Tom Hill – NHM

 

23 Sept - 4.00 pm

 

Earth Sciences Seminar Room (Basement, WEB 05)

 

A sediment core extracted from Queen’s Sedgemoor, Somerset Levels, has undergone high resolution radiocarbon dating. Subsequent directed micropalaeontological (palynological, diatom and calcareous microfossil) analyses focussed on the sedimentary sequence associated with the Mesolithic and early Neolithic periods.

 

This talk summarises the radiocarbon results and associated multiproxy analyses for the sedimentary sequence. Radiocarbon dating has identified a sequence dating back to the Mesolithic period (7.6ky BP). Microfossil evidence indicates hydroseral succession has taken place, with  the initial establishment of a freshwater lake, prior to undergoing terrestrialisation and eventually developing into a raised bog.

 

Holocene sea-level change also influenced the sedimentary archive. Due to a rise in relative sea level c. 6.7ky BP, subsequent coastal inundation and estuarine sedimentation took place, hereby associated with the Lower Wentlooge Formation of the Somerset Levels. Poor microfossil preservation was encountered within the section associated with the Mesolithic-Neolithic transition, but a clear picture of landscape change is presented for the sedimentary archive, with microfossil and microscopic charcoal evidence indicative of landscape modification by humans since the late Mesolithic.

 

More information on attending seminars at http://www.nhm.ac.uk/research-curation/news-events/seminars/

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Tom Richards from the Museum's Life Science department is an author on a paper in Nature that explores the genome of one of the most abundant species of planktonic plant - the coccolithophore Emiliania huxleyi.  Coccolithophores occur in great numbers in the ocean: the chalk cliffs at Dover are made up of the remains of their calcium carbonate skeletons.

 

The World's oceans are tremendously complex.  Currents move over thousands of kilometres, some descending as they are cooled by weather systems, or mixing at the surface with fresh waters, sediments and nutrients from continental rivers.  Life is immensely diverse, ranging from corals to the deep-sea vent faunas.  The highest biomass of life is in the shallow seas near to land, but the open ocean contains a constantly shifting system of tiny planktonic organisms ranging from bacteria to single-celled plants to grazing zooplankton and their predators. 

 

These planktonic ecosystems change with currents, seasons, nutrient availability and predation. Their growth, population explosions, deaths and decline interact with the planet's cycling of carbon and other nutrients.  These interactions are important in understanding ocean productivity and climate: there are links to carbon dioxide fluctuation, for example, as the plants absorb it during growth and release some at death.  Despite the tiny size of the organisms, their huge numbers over two-thirds of the planet's surface means that their role in planetary systems is very significant.

 

E. huxleyi experiences huge population explosions in the open ocean - planktonic blooms. Some species of phytoplankton bloom under very particular conditions of temperature and nutrient availability, but E. huxleyi thrives in a wide range of conditions, occuring from the warm waters of the equator to polar regions.

 

NaturalHistoryMuseum_PictureLibrary_033355_Comp.jpgEmiliania huxleyi, showing the distinctive calcium carbonate plates that cover its exterior. 

These may have important protective and light-reflecting qualities for the organism.

 

The paper finds that E. huxleyi strains from different areas share a core genome - this gives them a robust abilty to resist the inhibiting and damaging effects of intense sunlight, together with genes that allow effective growth in low phosphorus conditions.  There are genetic differences between the strains that lead to distinct abilities to thrive in different nitrogen, ammonia and metal conditions.  It seems that this, and other characteristics, give E. huxleyi the ability to bloom in very different oceanic environments - it is described as a species complex because of its genetic diversity.

 

This work will enable scientists to understand better the responses and influences of this very widespread species, and to investigate the complex processes and systems of the ocean that determine productivity and influence climate change.

 

Read, B.A. et al. (2013) Pan genome of the phytoplankton Emiliania underpins its global distribution. Nature doi:10.1038/nature12221

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Palaeontology Department Seminar

 

Thursday 1st September Neil Chalmers Seminar Room, DC2, 1600

 

Sampling, modelling, and making sense of the fossil record of diversity

 

Dr. Andrew B. Smith, Department of Palaeontology, NHM


While we can sample the available rock record effectively for its fossil content, the record we are sampling is itself biased.  Understanding and quantifying this bias is key to developing better estimates of diversity over time, and various ways of estimating rock record bias have been proposed.  Recent criticisms of these approaches by Benton and co-workers are shown to be misplaced or unfounded.

 

To demonstrate by how much the fossil record is distorted by unavoidable sampling inequality, the diversity of planktonic microfossil clades are estimated from two independent records – that of land-based outcrops and deep-sea cores.  These differ markedly, with each tracking its respective record of rock accessibility over time. However, modelling and subsampling approaches to the two very different records converge on a single underlying pattern, showing that these are powerful approaches for recovering less biased estimates of how past diversity has changed over geological time.

 

Contact: Greg Edgecombe g.edgecombe@nhm.ac.uk