M.Phil. dissertation abstracts 2003 - 2004
Copies of these dissertations will be held in the University of Cambridge, Department of Geography Library.
An Investigation of Mediterranean Tephras in the Black Sea (supervisor: David Pyle)
This project concerns the sediment characterisation of a core or cores drilled in the Black sea, including the identification of potential tephra layers. A sequence stratigraphy and chronology would then be constructed for the core(s), using tephra layers as chronological anchor points and possibly 14C dating of organic sediments. This would provide data on the palaeoenvironments of the region and further expand our knowledge of Mediterranean tephra dispersal.
- Preliminary survey of cores at Woods Hole Oceanographic Institution (WHOI) to determine sampling strategy.
- Sample cores and bring back to the Britain.
- Sediment characterisation involving XRF scanner (if possible), Magnetic Susceptibility, LOI leading to identification of tephra layers.
- Investigation of tephra layer possibly requiring micro-tephra analysis. If micro-tephra extraction techniques were to be used then facilities would be required for EMPA. It is preferable to measure the geochemical fingerprint of the tephra by using the WDS technique although the EDS technique is faster and cheaper (Both are available in Earth Sciences).
- If possible, an organic sample would be sent for 14C dating to provide further anchor points.
- Construction of a relative chronology constrained by ‘tephra’ anchor points.
Philip CurryQuaternary Sedimentary Record from near the Larsen C ice shelf. (supervisor: Carol Pudsey)
I document the analysis of marine core VC331 taken by BAS on Cruise JR71 in 2002 on the margin of the Larsen-C ice shelf, and to compare it with a previously analysed core taken from an area formerly covered by the Larsen A ice shelf. Specific questions to be answered are:
- Whether the Larsen C ice shelf has collapsed previously in the Holocene.
- Does a comparison between the two cores give clues why the Larsen A ice shelf has collapsed, whereas the Larsen C ice shelf remains stable?
The core is analysed for its lithogenic components, particularly: grain size (sand/silt/clay) - and interpretation in terms of (i) glacial supply, (ii) any sorting by bottom currents.
and morphology – interpretation in terms of degree of transport, operation of Antarctic Circumpolar Current. I also investigate the relative overall abundance (not individual species) of diatoms, though I would look out for one particular marker sea-ice species. Previous cores from the region have not contained forams, so this will not form part of the analysis.
The work was mainly carried out at BAS, where the core is located. I have the run of the BAS laboratory to prepare samples, and the use of their Malvern particle size analyser, and petrographic, stereo binocular and high powered microscopes to investigate smear slides, identify rock grains, and diatom abundance respectively.
No other core from the locality of the Larsen C ice shelf has/or is being studied, so in this respect, the work I shall be doing will be original. Should the results justify it, Carol Pudsey has suggested publishing a paper in our joint names.
A palaeoenvironmental reconstruction of the Bronze Age archaeological site at Fengate, Nene Valley.
Fengate is located on the northern side of the River Nene system on terrace gravels where the River Nene drains into the Fen basin (French, 2003). The site itself is a shore at the edge of the Fen basin, with the gravels giving way to peat further to the east. French, 2002, notes that the gravels at Fengate were the scene of later Neolithic and Bronze Age dispersed settlement, which was associated with elaborate field systems. Pryor, 1980, suggests that this is one of the largest prehistoric field systems in Europe.
The area of the site is significant since it is located next to the Bronze/early Iron Age ritual site of Flag Fen (Pryor, 1986). A Palaeoenvironmental reconstruction at Fengate would aid the understanding of the environmental and landscape changes that occurred and may have affected, and even been caused by, the population at this time. The vegetation environment could be compared with that at Flag Fen, described by Scaife, 1992. The site was occupied into the Iron Age, with re-occupation until the later second century AD. This study however would investigate just the Bronze Age period, for which an entire preserved sequence has been dated by Boreham. The area is in the southern Fens, where the correlation of similar fen deposits over long distances is difficult. Hall (1992) notes that each Fenland embayment or micro-region has to be studied individually, and so this study would aim to investigate the Fengate/Northey landscape.
Analysis of phytoliths from the teeth of Quaternary mammals: dietary
and environmental information
In this study, I extract, identify and interpret phytoliths from the teeth of Quaternary herbivores. Phytoliths are silica deposits that form between and within the cells of many mono- and dicotyledons. They are present in living plants, in the soil, and can also be incorporated into the dental calculus of animals over the course of their lifetime. They attain different shapes depending upon the type of plant, and in which plant tissues, they are deposited. By studying their morphology under a microscope, it is often possible to identify the kind of plants from which different phytoliths are derived. In many cases, particular species are not identifiable but it is generally possible, for example, to distinguish grasses from non-grasses, and C3 from C4 grasses. Techniques of phytolith identification have been developing since the 1950s, and it has been employed both in archaeological and palaeontological work. Analysis of phytoliths can be a useful method of archaeo- or palaeo- environmental reconstruction, as phytoliths are one indicator of the kind of plant assemblages that once grew at a given locality. Along with other forms of evidence, they can contribute towards the overall picture of a local environment in the past. An additional layer of information is obtained when the phytoliths analysed are extracted from the teeth of fossil animals. As well as aiding reconstruction of an animal’s environment by indicating some of the plant species that it encountered, they also provide evidence of its diet over the span of its lifetime.
Armitage (1975) was the first to extract phytoliths from fossil animal teeth recovered from archaeological sites, in order to determine their diet. No further work was published in this research area until the 1990s, largely due to limitations of phytolith identification techniques that existed up until that point. However, the science has developed considerably since the 1970s, and several published studies have described the extraction and analysis of phytolith material from animal teeth. For example, a study by Gobetz and Bozarth (2001) into phytoliths from the teeth of Late Pleistocene Mastodon Mammut americanum from North America provided new evidence of this species’ diet. The results showed that grasses comprised a far larger proportion of the Mastodon’s diet than previously believed, demonstrating the value of phytolith analysis as an alternative source of evidence.
I study phytoliths from the teeth of mammals from the Quaternary of Great Britain, under the joint supervision of Dr Adrian Friday (Cambridge Zoology Museum) and Dr Marco Madella (McDonald Institute). This study will involve removing dental calculus from herbivore teeth using dental probes, extracting phytoliths from this material by dissolving it in acid, mounting the phytoliths on slides, and identifying and quantifying the types of plants represented in the samples. As an initial step in this research, it may be feasible to trial the phytolith extraction technique on modern herbivore teeth such as cattle before moving on to Quaternary specimens. Possible museum specimens for this study are available from the Cambridge University Museum of Zoology, and Dr Madella’s laboratory is equipped for phytolith analysis. After analysing the phytoliths extracted from animal teeth, I will discuss the data in the context of the literature which already exists on the studied species’ diet and environment, to determine whether the phytolith evidence confirms what is already known, or is in conflict with existing lines of evidence. In this way, I plan to exploit an underutilised evidence source to provide an alternative perspective on the diet and environment of Quaternary herbivores.
Dating the Graig Goch Landslide Dam, and reconstructing the early-mid
Holocene Palaeoecology and Vegetational History of Meirionnydd, Mid-Wales.
(Supervisor: Charles Turner)
The Graig Goch landslide dam is situated in the upper Afon Dysynni valley in Meirionnydd. The slide has blocked the Afon Dysynni River, forming a landslide dammed lake, called Tal-y-llyn.
The slide is thought to have occurred in two distinct stages, with each stage capable of damming the Afon Dysynni. The volume of material deposited during the movements is thought to be in the order of 40 million cubic metres, but may have been up to 50 million cubic metres. These form a deposit that span the 400 metres wide valley, and extend 1200 metres down the valley. The landslide dam is 90-100 metres thick, and is breached by a 15-20 metres deep gorge cut by the river. Where the Afon Dysynni enters the breach from the lake, about 20 metres of slide debris lies below the river bed level, and the river does not reach the bedrock anywhere in the dam area.
When the slides took place is an area of great uncertainty. There are three main scenarios for the origin of the slides. The first is that glacial scour left the valley sides too steep and high to support their own weight, thus when the glaciers retreated removing the support for the valley sides, they collapsed. The second theory is that they were left unstable by glacial erosion, but persisted until after the glaciers had retreated before collapsing. Finally, the landslide may have been a result of seismic activity on the Caledonian Bala Lineament, of which the Tal-y-llyn Fault is the local component.
Hutchinson and Millar observed that the first slide had evidence of periglacial activity on the exposed slide surface, while the second slide is not thought to have been subject to periglacial activity. This can be used to put time constraints on the two landslides. The first must have taken place at least before the Loch Lomond Stadial, whilst the second must have taken place after it.
The aim of the investigation is to reconstruct the palaeoecology and vegetational history of the Afon Dysynni valley by palynological analysis of a core. The results will give a good reconstruction of the vegetation of the area, which may be complimented by macrofossil evidence. Once this has been achieved, it should be possible to compare the palaeoecology of the area to other records in the region for which robust chronologies have been established. This will enable the inference of dates for the core, and allow the dating of the Tal-y-llyn landslide. This date will not necessarily be precise, but will more likely be in the form of an assignment of a window of time within which the event took place.