Project staff and project resumes

Project title

The Sarup Sø Project (Part 1)
Interdisciplinary investigations of the interactions between cultural-, landscape- and lake-development at Sarup, Funen, Denmark. Sarup lake

Project scientists
Emily Bradshaw (post-doc) - egb@geus.dk
Peter Rasmussen - per@geus.dk

Funding source
The Danish Research Council for the Humanities www.forsk.dk/shf/ ) and GEUS

Project description
The introduction of agriculture ca. 6,000 years ago represents one of the most critical changes in the cultural history of Denmark. Archaeological finds provide direct evidence for early land-use (e.g. cereal grains, animal bones, flint axes, plough-marks) but offer little information about the effects of agriculture on the contemporary landscape and environment. Palaeoecological methods pollen and palaeolimnology can be used to shed light on these impacts. 60 years after Johannes Iversen's classic work describing Stone Age land occupation, the so-called 'landnam' phase (Iversen, 1941), this new project has been instigated in order to focus on the relationships between cultural-, landscape- and lake-development during the first 1000 years of Denmark's agricultural history. The site chosen for this study is Sarup Sø, Funen. The region surrounding Sarup is a unique archaeological area in Europe, with exceptional archaeological finds and settlements which give detailed information about cultural changes in the early Neolithic. The project aims to establish an accurate radiocarbon chronology for the lake sediment record and thereby correlate cultural development with vegetation and terrestrial change (through pollen and charcoal analyses); soil erosion (through sediment and mineral magnetic analyses) and nutrient enrichment of Sarup Sø (through diatom and pigment analyses). Sarup lake

Reference
Iversen, J. 1941. Landnam i Danmarks stenalder (Land occupation in Denmark's Stone Age). Danmarks Geologiske Undersøgelse, Series II, 68 pp.

Post-doc work
Emily Bradshaw's contribution to the project is the diatom analysis and the application of diatom-phosphorus calibration models to reconstruct past nutrient concentrations in Sarup Sø.

Project Title
The Sarup Sø Project (Part 2)
High-resolution study of natural aquatic variability utilising the annually laminated (varved) sediments from Sarup Sø, Funen, Denmark

Project Description
Annually-laminated (varve) sediment core from Sarup Sø

The first find of annually laminated (varved) Holocene lake sediments in a Danish site - Sarup Sø (Rasmussen et al., 2002) - presents exciting possibilities for palaeoecological and palaeoclimatological studies. The research is in collaboration with Bent Vad Odgaard, University of Aarhus. Bent leads a multi-disciplinary project to study the Sarup Sø varves, funded by the Danish Research Council for Natural Sciences. Emily Bradshaw's project aims are i) to assist in the establishment of a varve chronology for the site and ii) to explore changes in the aquatic ecosystem, prior to major human impacts at the site, and so influenced only by natural external (e.g. climatic) and internal (e.g. biological) processes, using diatom, biogenic silica, and palaeo-pigment analyses.

Funding source
The project is funded through the Danish Research Councils project Agrar 2000

Project description
This project is a continuation of a Ph.D. project carried out at GEUS 1999-2003 (Nielsen, 2003). The thesis is available from the author ( abn@geus.dk

A calibration data set, consisting of pollen assemblages from lake sediments dating from around AD 1800, and land cover on historical maps from the same period has been collected. 30 lakes between 3.5 and 30 ha in area, from different parts of Denmark were selected as calibration sites. This dataset has been used to analyse quantitative relationships between pollen assemblages and landcover, to estimate the relevant source area of pollen (Sugita, 1994) for small Danish lakes, to provide an empirical validation of the POLLSCAPE model (Davis, 2000; Sugita, 1993; Sugita et al., 1997) for simulating pollen sedimentation from a vegetation map, and to apply and test models for reconstructing landcover from pollen assemblages.

The historical analogues approach was chosen, because extensive changes in the Danish cultural landscape during the past two hundred years has made it impossible to find analogues for older cultural landscape, at least of the spatial scale reflected by pollen assemblages from lake sediments (Nielsen and Odgaard, 2004; Odgaard and Rasmussen, 1998; Odgaard and Rasmussen, 2000).

Summary of results so far
The relevant source area of pollen (RSAP) for the 30 sites was estimated to ca. 1800 m in radius. It did not seem to depend on wind speed or pollen dispersal properties. The empirical estimate of RSAP was a few hundred meter larger for sites in western Jutland than for the sites in eastern Denmark. The hypothesis that this was caused by a large difference in average patch size of the vegetation in the two regions was supported by a series of simulations.

The POLLSCAPE model was used to simulate pollen deposition in the calibration lakes from the historical plant abundance, and the simulated pollen proportions were compared to those observed in the lake sediments. Two sets of pollen productivity estimates, from southern Sweden (Broström, 2002; Sugita et al., 1999) and western Norway (Hjelle, 1998) were used in the simulations. For most taxa, there was a positive correlation between simulated and observed pollen proportions. The closest relationship between observed and predicted values was obtained using only 4 taxa (Trees, Poaceae, Cerealia and Calluna), because these were easiest to quantify based on the land cover signatures on the maps.

Estimates of pollen productivity and background term using ERV submodel 2 are applied to the AD 1800 pollen counts from nine test sites, which are not included in the calibration dataset, and distance weighted plant abundance around these sites is reconstructed using the inverse form of ERV submodel 2. Reconstructed distance weighted plant abundance is compared to that estimated from historical maps.

Ongoing work
The existing historical calibration dataset will be supplemented with a dataset of pollen assemblages in the surface sediment of the lakes, and modern landcover. This will allow a more detailed analysis of the effects of wind speed and direction on pollen dispersal and deposition, and hopefully to a more robust validation of the POLLSCAPE model than was possible based on historical analogues.

The Landscape Reconstruction Algorithm proposed by (Sugita and Walker, 2000) will be tested on the data. This involves counting pollen assemblages from a number of large lakes (over 1 km2), and using these to estimate regional pollen loading in different parts of the country, because this contributes to the pollen sedimentation in the smaller lakes, as well as the local vegetation.

If successful, this approach will allow quantitative vegetation reconstruction for periods in the past, based on pollen records from large and small basins. This, more detailed quantitative interpretation of late Holocene pollen diagrams than is currently possible will hopefully lead to a better understanding of the history of the cultural landscape.

References
Broström, A., 2002. Estimating source area of pollen and pollen productivity in the cultural landscapes of southern Sweden -developing a palynological tool for quantifying past plant cover. Lundqua Thesis 46, Lund University, Lund. Davis, M.B., 2000. Palynology after Y2K -Understanding the source area of pollen in sediments. Annu. Rev. Earth and Planet. Sciences 28 , 1-18.

Hjelle, K.L., 1998. Herb pollen representation in surface moss samples from mown meadows and pastures in western Norway. Vegetation History and Archaeobotany 7 , 79-96.

Nielsen, A.B., 2003. Pollen based quantitative estimation of land cover - Relationships between pollen sedimentation in lakes and land cover as seen on historical maps in Denmark AD 1800, Danmarks og Grønlands Geologiske Undersøgelse Rapport 2003/57. GEUS, Copenhagen, 135 pp.

Nielsen, A.B., & Odgaard, B., 2004. The use of historical analogues for interpreting fossil pollen records. Vegetation History and Archaeobotany 13 (1), 33-43.

Odgaard, B.V., & Rasmussen, P., 1998. The use of historical data and sub-recent (A.D. 1800) pollen assemblages to quantify vegetation/pollen relationships. In: Gaillard, M.-J., Berglund, B. (Editors). Paläoklimaforschung. Gustav Fischer Verlag, 67-75.

Odgaard, B.V., & Rasmussen, P., 2000. Origin and temporal development of macro-scale vegetation patterns in the cultural landscape of Denmark. Journal of Ecology 88 , 733-748.

Sugita, S., 1993. A Model of Pollen Source Area for an Entire Lake Surface. Quaternary Research, 39(2): 239-244. Sugita, S., 1994. Pollen representation of vegetation in Quaternary sediments: Theory and method in patchy vegetation. Journal of Ecology 82 , 881-897.

Sugita, S., Gaillard, M.-J., & Broström, A., 1999. Landscape openness and pollen records: A simulation approach. The Holocene 9 (4), 409-421.

Sugita, S., MacDonald, G.M., & Larsen, C.P.S., 1997. Reconstruction of fire disturbance and forest succession from fossil pollen in lake sediments: Potential and limitations. In: Clark, J.S., Cachier, H., Goldammer, J.G., Stocks, B.J. (Editors), Sediment records of biomass burning and global change. Springer-Verlag, Berlin 387-412 pp.

Sugita, S., & Walker, K., 2000. Landscape Reconstruction Algorithm for estimating vegetation changes from pollen records: A case study in the Upper Great Lakes region using modern and presettlement pollen-vegetation data sets., AGU Fall Meeting, San Fransisco.

Supervisors
Antoon Kuipers Ph.D., (Geological Survey of Denmark and Greenland), Professor Øjvind Moestrup (Botanical Institute, University of Copenhagen) and Nalan Koç Ph.D. (Norwegian Polar Institute).

Project partners
Geological Survey of Denmark and Greenland (GEUS), Botanical Institute at the University of Copenhagen, National Museum of Denmark, Durham University, Amsterdam Free University, GEOMAR Institute in Kiel, and the Netherlands Institute of Applied Geoscience TNO (NITG).

PhD description
The Ph.D.-project is affiliated to the project "HOLOCENE PALEO-HYDROGRAPHIC CHANGES IN GREENLAND COASTAL WATERS AND FJORDS, AND POSSIBLE IMPLICATIONS FOR HUMAN SETTLEMENT", and funded by the Special North Atlantic Research Programme of the Danish Research Agency.

While global annual average temperature has been steadily rising since the early 1980's, a cooling trend in West Greenland temperature records has been observed during the last decade. This adds to the records of slight cooling in the Labrador Sea and southern Greenland since the 1960's.

Since the mid 1980's, changes have been observed in the North Atlantic deep water formation; a cessation of convective deep water renewal has been reported in the Greenland Sea, and convection has started to prevail in the Labrador Sea. These areas off Greenland are, apart from Antarctic waters, the only sites with direct exchange between the atmosphere and the deep ocean.

Palaeoceanographic studies and coupled atmosphere-ocean models indicate that climate changes in the North Atlantic region are closely related to changes in surface circulation and in the production of North Atlantic deep water.

In this project cores will be taken from south-west and west Greenland in order to compare regional hydrographic patterns. The Ph.D.-project will take a multi-proxy palaeoceanographic approach using diatoms, stable isotopes as well as other relevant geo-chemical and sedimentological records from high-resolution sediment cores. Diatoms are sensitive to environmental changes, e.g. salinity, temperature and nutrients, and therefore valuable indicators when determining the hydrographic conditions. As salinity and sea surface temperatures can provide hydrographic proxies, the project attempts to reconstruct past changes in sea surface temperature and salinity by the application of diatom-based transfer functions.

Through comparison with Greenland lake- and ice core data, the work will contribute to a better understanding of atmosphere-ocean interaction and long-term climate patterns of the seas around Greenland. Comparison with relevant Holocene climate records from north-west Europe may help explaining the interrelationship between the cooling trend observed on Greenland and documented global (Northwest European) warming.

The record of Paleo-Eskimo cultures on Greenland's west coast shows various major immigration and cultural stages of which the initial phase of the oldest (Saqqaq) culture has been dated at near 4,3 ka. In addition, the southwards expansion of the Thule culture coincided with the beginning of the Little Ice Age, 1200-1300 AD. Archaeological evidence from Western Canada and eastern North America shows much earlier human occupation of high-latitude areas, i.e. at the Pleistocene-Holocene boundary. It thus seems that the Holocene southward migration of Inuit in Greenland occurred when Holocene climate deteriorated, i.e. in Middle Holocene times and at the beginning of the Little Ice Age. This may be coincidence, or might be related to changes of the (marine) physical environment directly affecting resource utilisation. The further objective of this project is to establish a highly detailed (AMS C-14) chronology focusing on Mid-Holocene and Little Ice Age-related hydrographic changes that could have implications for the Eskimo and Norse settlement stages. In order to study possible links between these changes and the physical (marine) environment and human settlement history, extensive dating of archaeological material is envisaged as well.

PhD working title
'Thrust faulting in Neogene and Quaternary sequences in the South-eastern Danish North Sea'

Supervisors
Holger Lykke Andersen, Department of Earth Sciences University of Aarhus , Finlandsgade 8, 8200 Aarhus N, Denmark (e-mail hla@geo.au.dk ) and
Peter Roll Jakobsen, The Geological Survey of Denmark and Greenland, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark (email prj@geus.dk

Funding source
The Geological Survey of Denmark and Greenland and The Danish Research Agency

Project description
An extensive system of shallow thrust faults situated in the south-eastern Danish North Sea is being mapped and analysed, based on a grid of 1565 km high-resolution multichannel reflection seismic data. The seismic data have been acquired during the years 1998 - 2001 in connection with the Standard Flex project (a joint venture project between Farvandsvæsnet, Søværnet, Århus Universitet and GEUS).

The thrust complex consists of disturbed, folded and thrusted sediments sliding on a weakly inclined basal décollement surface. The layers beneath the basal décollement surface are undisturbed; thus the thrust complex is interpreted as a glaciotectonic thrust complex. The dimensions of the thrust complex is one of its kind, with thrust sheets varying in length from less than 100 m till more than 1,5 km. The thrust faults emerge from depths down to 375 m, and the whole thrust complex covers an area of more than 15 km times 40 km. Correlation with the well S-1 in the Danish part of the North Sea indicates that the décollement surface is located in the Mid Miocene. The north-south striking deformation front is situated 35 km from the west coast of Jutland. Similarities with the onshore geology are being investigated in order to place the complex into a regional glaciostratigraphic context. The methods include mapping of glaciotectonically dislocated Miocene deposits onshore and lithostratigraphic analysis of a till unit in the Rømø-2 well.

In this particular geological site in the SE Danish North Sea it is possible to obtain an unprecedented insight in a glaciogenic thrust fault system. Mapping and understanding of the thrust structures is expected to provide a significant contribution to the conception of similar features in the North Sea. Furthermore, the study will contribute to the regional geological interpretation of the Miocene offshore and onshore, and thus provide insight of importance for e.g. hydrogeological investigations.

Ph.D. description
This Ph.D. project is funded by the COGCI-school Copenhagen Global Change Initiative and will investigate the recent discovered changes of the South Greenland ice-sheet margin. The major aim of this study is the development of a numerical ice-dynamic model, which will analyse the effect of changes in surface elevation and possibly in mass balance conditions. To evaluate model results field measurements are collected by GEUS, which established a mass-balance transect in 2001 along a South Greenland outlet glacier (Sermilik Bræ).
This transect includes two automatic mass-balance stations and four ablation stakes. The sophisticated mass-balance stations provide climate data such as wind speed, wind direction, air temperature, humidity, radiation and mass-balance observations (snow accumulation, snow/ice ablation, surface velocity). The Goddard Space Flight Center (NASA), an associated partner institution, performed additional measurements of the ice-surface and bedrock topography along the established transect. The dynamic modelling approach will mainly aim at investigating the dynamics of short-term glacier fluctuations caused by climate change.

Previous research documents glacier observation and glacier stand for scattered localities in southern Greenland over the past 100 years. Here the study will use information conveyed by different sources to establish a physical history of glacier response behaviour. The historical and present changes of the southern Greenland ice sheet will be examined by ice-sheet margin observation using a combination of airborne photographs and satellite images in order to determine the historical glacier positions over the last decades. The historical and present investigation of the ice-margin fluctuation will be used to evaluate the results from the ice-dynamic model.

Remote views of Sermilik Glacier area. A: Aerial photograph obtained 1953; B: Satellite image from Landsat 7 obtained in 2000. The chart shows the measured retreat of the glacier terminus of Sermilik Glacier determined from available aerial photographs and satellite images. The total retreat accumulates to more than 4.7 km since 1953

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