Our areas of specific interest are Environmental magnetism and palaeomagnetism applied to sediments and soils. Current active research areas are focused on:
Our areas of specific interest are Environmental magnetism and palaeomagnetism applied to sediments and soils. Current active research areas are focused on:
Environmental magnetic studies relevant to climate change in the Pacific, Indian and Atlantic Oceans and the Chinese Loess Plateau (work on the latter funded most recently by the Leverhulme Trust). Magnetic proxies for atmospheric dust records both in the oceans and on land, and their relevance to climate change (NERC-funded, 2001-2002). Studies relating to sediment diagenesis, its effect on the preservation of magnetic minerals and the consequences for palaeomagnetic and environmental magnetic records. Magnetostratigraphic studies (particularly Triassic-related) both in the UK and elsewhere. Rock magnetic studies of synthetic sub-micrometre magnetite and other important remanence-carrying phases, through MAG-NET (EU-funded Network for Mineral Magnetic Studies of Environmental Problems). Characterizing sediment budgets and provenance using magnetic methods. Magnetic proxies for pollution (especially with regard to measurement of leaves as particle receptors, and of east European soils). Magnetic proxies of rainfall; palaeorainfall reconstruction (NATO-funded).
Palaeoclimate and palaeoenvironment from magnetic properties of buried Quaternary palaeosols. Rates of loess and pedogenic magnetite accumulation in Recent loess soils, China. Links between palaeoclimatic change and magnetic signatures in sediments from the NE Australian Margin Magnetostratigraphy of the Lower and Middle Triassic, Spitsbergen. Magneto- and lithostratigraphy of the Pliocene sediments, Red Sea Coast, Safaga to Quesir, Egypt. The magneto-mineralogy of the Late Triassic, Lunde Formation The source of a magnetostratigraphy in Cretaceous Chalk from Southern England
Palaeoclimate and palaeoenvironment from magnetic properties of buried Quaternary paleosols.
(1999-2001)
This is a NATO-funded collaborative project with Drs Alekseev, Alekseeva and Demkin, Institute of Basic Biological Problems, Russian Academy of Science, Pushchino, Moscow. In the region of the Russian steppe, from the North Caucasus to the Caspian lowlands, a series of buried soils occurs, associated with funeral mounds. Variations in the properties of the buried soils identify key shifts in soil-forming climate (especially in precipitation) in this presently semiarid region. Burial of the soils was effectively instantaneous (i.e. over a few days), as the mounds were constructed. Time control is provided by the clear cultural/physical distinctions in the artefact assemblages recovered from the mounds. The magnetic-climate link is quantified by the strong direct correlation between the pedogenic susceptibility of modern soils across the steppe and present-day precipitation.
MAG-NET: Network for Mineral Magnetic Studies of Environmental Problems.
(1998-2001)
The Centre for Environmental Magnetism and Palaeomagnetism at Lancaster is a member of the EU-funded Mag-Net project. The network of European environmental magnetic laboratories involves ten institutions: the University of Southampton, the University of Liverpool, the University of Lancaster, the University of Utrecht (The Netherlands), the University of Munich, the University of Leoben , Eidgenossische Technische Hochschule, Zurich, the Istituto Nazionale di Geofisica, Rome, CEREGE, Marseilles and the University of Madrid. The research goals of Mag-Net are to identify climate variability (especially desiccation episodes) over mainland Europe over centennial to millennial timescales and to identify and mitigate the impact of anthropogenic particulate pollution.
To achieve these goals, the following research aims have been identified:
Rates of loess and pedogenic magnetite accumulation in recent loess soils, China.
The thick sequences of windblown dust (loess) and interbedded buried soils in NC China span the last ~2 million years of Earth’s history, and constitute the longest , most detailed record of climate change yet found on land. These sediments carry a very detailed magnetic record of climate change. The soils contain higher concentrations of strongly magnetic iron oxides, of distinctively ultrafine grain size (< ~0.05m m); the less weathered loess layers contain much less of this material. These differences can be easily and rapidly quantified by measuring the magnetic susceptibility of the sediments. The aims of this project, funded by the Leverhulme Trust, are to: investigate the basis for calibration and translation of magnetic susceptibility into the key climate parameter, palaeorainfall, for the area of the Chinese Loess Plateau, and to obtain the most detailed and accurate data so far on rates of dust accumulation and pedogenic susceptibility development, by magnetic and pedological analyses, and luminescence dating of undisturbed Recent soils and loess/soil sequences. It is a collaborative project with Prof. Ann Wintle, Institute for Geography and Earth Science, University of Wales, Aberystwyth, and Prof. Roy Thompson, Dept. of Geology & Geophysics, University of Edinburgh.
(1995-1997)
A 2-year project funded by the Leverhulme Trust examined the causal links between palaeoclimatic change and magnetic signatures in sediments collected during ODP Leg 133 (Holes 819 to 823), North-eastern Australian Margin.
Particularly noteworthy in these sediments is the relationship between magnetic susceptibility and oxygen isotope records. Prior to the formation of the Great Barrier Reef, their relationship is inverse (i.e. high magnetic susceptibility during interglacial stages), but switches to a corrupted positive correlation after Reef formation.
Detailed rock magnetic and mineral magnetic investigation of these Leg 133 sediments identify variations in sediment magnetic mineralogy, related mainly to the degree of diagenesis experienced by the sediments post-deposition. Magnetic sources for these sediments include aeolian dust, magnetosomes from magnetotactic bacteria and possible riverine inputs, especially during sea level lowstands (glacial stages). The transect of holes, from proximal to distal across the Coral Sea, from Leg 133 offers the possibility of producing a spatial, as well as temporal, record of these changes.
Globally synchronous reversals of the earth’s magnetic field have proved major tools for dating and correlation in sediment sequences deposited since the early Cretaceous. The aim of the project, is to define an age-calibrated, magnetic field reversal sequence (magnetostratigraphy) for the Triassic. The Triassic is attractive, for using magnetostratigraphy, since biostratigraphy of this interval is plagued by faunas and floras, which have localised correlation potential. If an accurate magnetostratigraphy could be established for the Triassic, it would be possible to link the ammonite biozones of the Arctic, the conodont/ammonoid zones of the Tethys realm and the palynological zones of terrestrial sequences in central and northern Europe. Such a framework has widespread implications for accurate correlation of geodynamic, climatic and biologic events world-wide.
The initial phase of the project is to study the Lower Triassic on Spitsbergen which spans the Griesbachian to Spathian stages. The Spitsbergen sequences serve as reference sections, for much of the Arctic Triassic on the Norwegian Barents Shelf, and beyond. A second phase is to extend the sampling through sections around the Arctic Ocean.
Further information can be obtained by contacting Mark Hounslow.
The Red Sea has attracted much interest from a geotectonic and sedimentological point of view because it provides a present day example of the early stages in a rifted passive continental margin. The Red Sea Region shows evidence of the classic uplift, and subsequent subsidence of the Red Sea basin margins, followed by creation of oceanic crust at the spreading centre in the centre of the rift. Uplift during the late Eocene, was followed by rift development, and subsidenece in the southern Red Sea in the late Oligocene. In the northern Red Sea, and Gulf of Suez the subsidence was progresively later, having commenced in the early Miocene. During the middle Miocene the Red Sea and Gulf of Suez became partially separated from the Indian Ocean and the Mediterranean which initiated the development of an episode of hypersalinity leading to the deposition of a sequence of middle to upper Miocene evaporites (the South Garib and Zeit Formations). This series of interbedded halite, anhydrite, claystone and carbonates may reach up to 4000m in the deepest depocentres in the centre of the rift where there is evidence of halokinetic deformation.
The initiation of sea floor spreading in the Red Sea during the lower Pliocene, combined with uplift of peripheral regions and reconnection with the Indian Ocean, brought about a dramatic change in depositional environments with a return to deep-marine normal salinity conditions in the centre of the Red Sea and coastal marine conditions on the flanks of the rift.
The sedimentary dynamics and facies evolution of the post-Miocene rift margin sediments are expected to be strongly influenced by the rift tectonics (margin uplift, and rift subsidenece), and also by salt tectonics, from the underlying evaporites. The details of this post-Miocene sedimentary evolution have been poorly documented. A magnetostratigraphic study was initiated as a tool to help constrain dating of the Pliocene sediments, particularly to better understand the interplay between tectonics, evaporite burial dynamics and sea-level change.
Deeply buried sandstone sequences can act as magnetic-recorders of the ancient magnetic field when they were originally deposited. The detailed mechanism of why this should occur is poorly understood.
This project was to determine the minerals responsible for the magnetic properties of the deeply buried (~3km) Lunde Formation sandstones in the Northern North Sea, using various magnetic measurements, scanning and transmission electron mincroscopy. The results show the magnetic properties are directly related to the effects of diagenesis in producing new magnetic minerals, and modifying the originally deposited magnetic oxides. Relict Cr and Mn bearing ferrimagnetic spinels now dominantly carry the remanent magnetization properties, as well as magnetic oxides formed within quartz and feldspar grains during their formation in the source rocks.
The extremely weakly magnetic Campanian Chalk of the Isle of Wight and Sussex, preserves the late Cretaceous reversals of the Earths magnetic field. However, the minerals which were acting as recorders of the magnetic field were not known.
Magnetic mineral extractions and various magnetic measurements were performed to identify the minerals responsible. Large amounts of bacterial generated magnetite were found, often in intact chains, which is mostly responsible for the preservation of the ancient magnetic field signal. This bacterial magnetite shows variation in both its amounts and morphology of the grains. This is caused by differences in the amount of diagenetic dissolution, and also perhaps by different depositional conditions, during the Cretaceous.