A palaeoenvironmental reconstruction of
late Holocene changes at Fulford Ings, York
A thesis submitted to the University of Manchester for the degree of
MSc in Environmental Monitoring, Modelling and Reconstruction
in the Faculty of Science and Engineering
School of Geography
Extract of the report
Table of Contents
List of Figures 4
List of Tables 6
Notes on copyright and the ownership of intellectual property rights 9
1. Introduction 11
2. Materials and Methods 15
2.1 The Study Site 15
2.2 The Cores 19
2.3 Analytical Procedures 21
3. Results 23
3.1 Troels-Smith 23
3.2 Volume Magnetic Susceptibility 26
3.3 Heavy Metals (Lead, Copper, Zinc) 27
3.4 Pollen 30
3.5 Macrofossils 33
3.6 Loss-on-Ignition 35
4. Analysis, Interpretation and Discussion 36
4.1 Precision of Heavy Metal Measurements 36
4.2 Chronological Model 36
4.3 Vegetational Cover in 1066 41
4.4 The Charcoal Bands 42
5. Conclusion 45
Appendix 1 – The Troels-Smith description system 55
Appendix 2 – Determination of heavy metal content of soil by nitric acid digestion 56
Appendix 3 – Pollen analysis preparation 57
Appendix 4 – Determination of organic matter content by loss-on-ignition 60
A series of cores, covering a total depth of 2380 mm, were extracted from a swampy area of Fulford Ings, a floodplain of the River Ouse just south of York, UK. The stratigraphy consisted mainly of clay with sand, lake mud, and organic matter, and distinct fine bands of charcoal at the base of the profile. A chronological model developed, by relating volume magnetic susceptibility and heavy metal measurements to the documented mining history of the Yorkshire Dales, dated the base of the profile to 1050 A.D. This model also showed that charcoal was increasingly abundant pre-1780 A.D. It is suggested that this reflects the history of smelting in the area, which relied on charcoal as a fuel prior to this date, later replaced by coal. Pollen grains were generally poorly preserved in the profile, and many grains were unidentifiable. However, the pollen grains present and the respective percentage assemblages suggested little change in vegetation between 1720-1860 A.D. and 1060-1080 A.D., at which time the Battle of Fulford took place on the site. The landscape, in both cases, was dominated by Gramineae (grasses), Cyperaceae (sedges) and Typha latifolia (bulrush), with relatively little tree pollen, similar to present day cover.
No portion of the work referred to in the thesis has been submitted in support of an application for another degree or qualification of this or any other university or other institute of learning.
Notes on copyright and the ownership of intellectual property rights
Further information on the conditions under which disclosures and exploitation may take place is available from the Head of the Department of Geography.
Charles Jones; Dave Shimwell; John Moore; Mike Clarke; Simon Robinson; Sarah Woolven and English Nature; landowners Mr Watts, Dick Reid, R. M. Stanley, Mr Shann, Sarah Blakeham, J. P. Birch; Colin Briden; Ben Moore and WYAS; Stephen Gordon.
Palaeoenvironmental reconstructions start from the premise that an environmental history can be preserved in the soil in the form of changes in macro- and microfossils, magnetic, chemical and physical properties. Sediment cores display distinct stratigraphies, and thus changes in these properties can be determined, analysed, and then interpreted as proxy environmental data. The fundamental idea is that changing environmental conditions will be recorded, as they occur, in the changing proxy environmental data in the sediment. The truth of this depends upon many factors, including both the depositional and post-depositional environments.
1.1 Previous Work
Palaeoenvironmental reconstructions have been undertaken in a variety of depositional environments. Much work has focused on interpreting cores taken from lakes and peat bogs (Clymo, 1984; Tallis, 1995; Blackford, 2000). However, work has also been undertaken on profiles from reservoirs and floodplains (Macklin et al., 1997; Lillie & Gearey, 1999a; 1999b; Owens et al., 1999). The type of environment cored, and the source of sediment, has important implications for the nature of the palaeoenvironmental reconstruction and the type of questions that may be addressed. Sediment sources are either autochthonous (internal, for example, from animal and plant groups living in that environment) or allochthonous (external, for example, from the atmosphere or catchment).
Ombrotrophic peat bogs receive no water from the ground and are fed by atmospheric input. They have therefore been used extensively to answer questions about industrial pollution and atmospheric deposition (Lee & Tallis, 1973; Oldfield et al., 1978; Richardson, 1986; Thompson & Oldfield, 1986; MacKenzie et al., 1998) and climate change (Aaby, 1976; Barber, 1985; Tallis, 1995; Blackford, 2000). Sedimentary profiles have also been used to reconstruct local vegetational change and fire histories (Tallis & Livett, 1994), as well as to answer specific questions relating to peat bog growth (Clymo, 1984) and erosion (Tallis, 1985; 1995).
Lakes, on the other hand, are fed both by their catchment and the atmosphere, as well as by groundwater. Sedimentary profiles from lakes have been used to show changes in atmospheric pollution (Brännvall et al., 1999). The remains of aquatic biota, such as diatoms, chrysophytes, chyronomids, ostracods, and Cladocera, provide long-term data on lake water chemistry (Charles & Smol, 1994), allowing the reconstruction of changes such as pH (Birks et al., 1990), nutrient levels (Bennion, 1994) and salinity (Fritz et al., 1991), to which the organisms are sensitive. Lake sediments can inform of climatic changes, such as air temperature (Lotter et al., 1997). Studies of Scottish lakes have been concerned with the early history of the lakes following deglaciation (14,000 to 10,000 years ago), their long-term development since then, and recent problems of change and pollution (Battarbee & Allott, 1994).
Floodplains, like lakes, are also fed by both catchment and atmosphere. The potential value of palaeoecological reconstructions of fluvial ecosystems has been recognised (Petts et al., 1989). They have been used to reconstruct local and regional vegetational change (Lillie & Gearey, 1999a; 1999b), as well as to determine the history of the river system (e.g. sediment source, flood history, channel location; Owens et al., 1999). Floodplain sediments often offer the best source of information about the past behaviour of a river basin for lowland environments (Owens et al., 1999). In particular, the stratigraphy of floodplain sediments can inform of both natural and anthropogenic (e.g. agricultural; Kukulak, 2000) environmental and geochemical changes over the period in which they were deposited (Hudson-Edwards et al., 1999a). Floodplain sediment profiles have effectively been used to document recent heavy metal pollution caused by mining and industrial activity (Macklin et al., 1997; Hudson-Edwards et al., 1999a; 1999b). Floodplain materials are, however, threatened by the effects of erosion and drainage (Van de Noort & Etté, 1999).
The properties used as proxy environmental data in each type of depositional environment, again, depend on the questions being asked. For example, mineral magnetic measurements are useful in reconstructing atmospheric pollution histories (Richardson, 1986), whilst charcoal fragments can inform of fire histories (Figueiral & Mosbrugger, 2000). Macrofossils, such as the remains of different plants with known ecological preferences, have been used to reconstruct climatic changes (Tallis, 1995) and diatoms have proved invaluable in the reconstruction of lake acidification (Battarbee et al., 1999). In most cases, however, a palaeoenvironmental reconstruction is strengthened by using a suite of different parameters (Brown, 2002). For example, magnetic parameters combined with charcoal analysis can produce a good fire history (Tallis & Livett, 1994; Gedye et al., 2000), as can pollen analyses combined with charcoal analysis (Emanuelsson & Segerström, 2002). Fossilized beetle remains and pollen analysis have been used together in the study of palaeoecosystems (Brown, 2002) and changing floodplain biodiversity (Brayshay & Dinnin, 1999).
The palaeoenvironmental changes recognised by means of proxy environmental data can be used to monitor long-term changes, since in many cases these records extend well beyond documentary evidence. Thus, it is vitally important to establish a chronology so that the timing, duration and speed of any change can be recognised. A variety of different dating techniques have been applied (Sowers et al., 2000), including: annual laminations; local stratigraphic markers such as pollen assemblages and heavy metal concentrations; the known decay of radioactive isotopes such as 14C and 210Pb, and the appearance of radioactive isotopes such as 241Am and 137Cs, relating to known peaks in their concentrations; tephrochronology; and carbonaceous particles. The various approaches can be used for different sediment types and each has its own limitations (Rutter & Catto, 1995).
1.2 Aims and Objectives
The main aim of this research is to attempt to establish the vegetational cover of the study site (Fulford Ings) in 1066, at which time the Battle of Fulford took place on the land. Various theories of the battle rely on the land being swampy, as it is today. According to the Icelandic saga of Snorri Sturlsson, the defending army were trapped by the invading Norsemen in a swamp. It has been suggestsed that this swamp was just north of Germany Beck (the drain just south of the boat house in figure 2), which was the main defensive line (Hammond, 1991; 1997; Jones, 2001).
This aim will be achieved by taking sediment cores from the site. A chronological model, based on volume magnetic susceptibility and heavy metal concentrations in the cores relating to a documented mining history of the catchment, will be developed in order to date the profile. Using this model as a basis, pollen assemblages from around the time of the battle will be compared with more recent assemblages in order to determine their similarity and thus reconstruct a vegetational history of the site. The pollen types found will also be compared with present day vegetation on the site.
As a result of carrying out this analysis it is expected that a fuller history of environmental change may be reconstructed. The subsidiary aim of this research is therefore to document this environmental history of the site. To achieve this, different types of proxy environmental data will be employed. The cores will be described according to the Troels-Smith procedure, and macrofossil and loss-on-ignition analyses will be undertaken.
2. Materials and Methods
2.1 The Study Site
2.1.1 The Ouse Catchment
The study site is Fulford Ings, a floodplain of the river Ouse about 2½ km south of York, in north-east England (figures 1 and 2). The Ouse, a predominantly unpolluted gravel-bed river (Owens et al., 1999), is one of two main rivers feeding the Humber estuary (Walling et al., 1998). The catchment area of the Ouse at York (SE 6055 5100) is 3332 km2 and major tributaries upstream of York are the Swale, Ure and Nidd, draining the southern part of the Yorkshire Dales lead-zinc fluorite-baryte orefield (Hudson-Edwards et al., 1999a; 1999b).
The Ouse basin is underlain by Carboniferous to Jurassic sedimentary rocks (figure 1) including limestones, shales, sandstones, thin coals, marls, mudstones, and chalks (Gaunt, 1994; Owens et al., 1999), which are overlain in many areas by glacial drift deposits such as boulder clay (Walling et al., 1998). Altitude varies, within the catchment, from 600 m AOD (above ordnance datum) in the Pennines, to less than 20 m AOD in the Vale of York. Average annual rainfall varies with this topography from 2000 to 600 mm/yr (Longfield & Macklin, 1999). The mean annual precipitation in the catchment is 906 mm/yr and runoff is 464 mm/yr (based on figures from above Skelton (SE 425 734), 5½ km upstream of York, over the period 1969-1990; Walling et al., 1998). Daily mean, instantaneous maximum recorded, and mean annual flood discharges at this point are 48.6, 622, and 302 m3/s, respectively (Longfield & Macklin, 1999).
There are no major urban areas in the catchment upstream of York (Walling et al., 1998), and correspondingly there is a low population density (Jarvie et al., 1997). There is also little woodland, and the land is mainly used for rural agricultural purposes, including growing arable crops and pasture for grazing livestock (Walling et al., 1998).
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