New Dating Techniques to Reconstruct the Environment and Climate Change in Dynamic Landscapes

A significant progress in the reconstruction and quantification of environment change will be achieved by the development of new innovative techniques in luminescence dating. This will result in an improvement of our knowledge about the dynamics of landscape alteration, such as periods of aggradation and erosion in fluvial systems, the dislocation of coastlines and the reconstruction of climate change from continuous sediment archives. The research topic “Geochronology” was benchmarked as “outstanding” during the evaluation of the LIAG in 2004.

Research Objectives – General Research Topic

Investigating terrestrial sediment archives of the past is imperative to learning and understanding the future impact of climate and environment changes. The Medieval climate optimum and the Little Ice Age are two historically recorded periods during which society was considerably influenced by climate and environment change. During the past 15 years, exceptionally strong rainfall events, giving rise to high magnitude floods in major Central European rivers, may be related to the global greenhouse effect. Models of future climate change predict a higher number of extreme weather events resulting in significant alteration of sensitive environments and landscapes along rivers and the coast. To provide a better insight into likely future climate and environmental szenarios, it is important to reconstruct past changes from the geological record, and then to use this information to test and improve predictive climate models.

Loess/palaeosol sequences, maar sediments, fluvial and coastal sediments represent terrestrial archives, which allow reconstructing the alteration of landscapes triggered by climate change during the geological past. Such studies require precise and accurate individual chronologies to quantify temporal surface processes and to correlate these records and so to investigate past scenarios in different environments of landscape alteration.

Luminescence dating methods encompass a suite of powerful new techniques with the potential for wide applicability in environmental research and archaeology. The basic physical principle is solid state dosimetry of ionising radiation; quartz, feldspar and other minerals have been used as natural dosimeters. Luminescence dating methods contribute valuable temporal controls for sediment sequences and have proved to be successful for the dating of aeolian, fluvial and coastal sediments. The deposition age of sediments, which is the time elapsed since the last exposure to sunlight, is determined by these methods. One principle advantage of luminescence dating methods is their general applicability; they can be applied in almost all sedimentary contexts, in many of which radiocarbon and other dating methods are not applicable. Recent advances in instrumentation and measurement protocols have played a key role in improving the dating of sediments from various environments. The dating range is between a few years and several hundred thousands of years, theoretically the upper dating limit is about 2 million years.

The topics for which funding is requested are of fundamental research, including methodological and technical improvements as well as the design and set up of a portable system for on-site measurements. The new features are used for work on the applied research topics. It is the aim to set up a more accurate and reliable chronological frame of climate and environment change from sediment sequences of various terrestrial and shallow marine deposits.

More detailed knowledge about the alteration of landscapes owing to weather events or climate change is required and is of vital interest in the surroundings of river systems and coastal areas.

(i)         Fluvial Dynamics:   Fluvial landscapes in modern floodplains and lower terraces are particularly sensitive to climate change. Extreme weather events such as the millenial flood of the year AD 1342 had a catastrophic impact on Man and the society and indeed a significant alteration of landscape, such as up to 15 m deeply incised canyons and reworking of 6 to 8 m thick fluvial sediments in southern Germany. The extent of the fluvial dynamics and the temporal succession of such events are not yet understood in either large or small rivers, such as the rivers Rhine and Aller, respectively. One of the aims of this project is to investigate more precisely than before the response of these two fluvial systems over the past 100,000 years and to establish a more reliable chronological framework for aggradation periods. Determination of the grain-to-grain dose variations will enable the more accurate calculation of deposition ages by minimising the age overestimation owing to insufficient bleaching and by improving the analytical error from ±10-15% to about ±5%. The use of a portable luminescence reader will greatly assist the field identification of the most suitable material for sampling and will allow the determination of the extent of Holocene landscape alteration by dating many more exposures in the field than is practicable by using laboratory methods.

Furthermore, the Pleistocene evolution of the Rhine system for the time period of the past one to two million years will be reconstructed based on a more reliable chronological frame. The climato-tectonic triggering of periods of aggradation and erosion including the uplift rate of the Rhenish Massif will be investigated quantitatively for the first time.

(ii)        Coastal Environment:   During the past 10,000 years, climate change and sea-level change, and extreme weather events have had a major influence on the human use of coastal environments owing to the significant alteration of coastlines. At the North Sea and Baltic coasts, large amounts of sediment have been mobilised and form extended accumulations, which are partly still active sand dunes (e.g. the barriere islands of the Frisian coast and the bay bars along the the Baltic Coast like Courland Spit). Recent applications of quartz OSL to coastal sediments have also shown the potential of these techniques for establishing chronologies on a decadal to century timescale for aeolian dunes, coastal sand flats and estuarine sands. There is no other dating technique than luminescence that is applicable on this time scale, and in the absence of historical records, almost nothing is known about changes in these very important landforms over the last 500 years. The exact temporal succession of this sediment mobilisation will be studied onshore and in shallow marine coastal areas of the North Sea and Baltic Sea

(iii)       Loess Environment including Maar Lake Sediments:  Loess is one of the most detailed terrestrial wide-spread high resolution archives of climate and environment change. Marine records and ice core records primarily record global climate signals, whereas loess/palaeosol sequences and peat layers reflect regional and local climate and environmental conditions in addition to global signals. Lake sediments accumulating in relict volcanic craters, have undergone continuous deposition of sediments since the eruption of the maar volcano, and so contain unique continuous local records of climate change.

Luminescence dating will be carried out to correlate the remains of dust storm events within maar sediments with those of the loess record from the East Eifel and Middle Rhine area. It is the aim of this project to set up a much more reliable chronological framework for the temporal successions of dust storm events including synchronous periods of increased aridity in Europe for the past 100,000 years than is known today. We will also focus on the longer time period of the past 300,000 years to set up a more reliable chronological framework for the duration, amplitude and periodicity of landscape alteration. Data on past dust fluxes over Europe on a high resolution temporal scale are essential for modelling the coupling of past climate with circulation patterns of dust content in the atmosphere, and thus improving the accuracy of climate change predictions. The methodological studies will include OSL, TT-OSL and IR-RF techniques and will be applied to older loess to determine more reliable age estimates for the time range extending 100,000 years. Thus, the age of Palaeolithic artefacts important for the evolution of hominides and intercalated in loess/palaeosol sequences of the Rhineland will be determined; and so exciting results will be achieved in the overlapping domain of Science and Humanities.