Tectonic studies

We use geochronology and thermochronometry to understand how continents deform and how surface topography develops over different spatial and temporal scales.

We want to understand the mechanisms and feedbacks that affect the Earth’s surface region which is important to explain tectonic processes, climate and ecological change past, present and future.

Our research is focused on sediment provenance and rock exhumation studies that encompasses a wide range of field areas, including many mountain belts;  Himalayas-Tibet, Alborz Mountains, Pyrenees, Taiwan, Altai, Canadian Rockies, European Alps, and Caucasus. This work is carried out with many UK and international collaborators.

Provenance studies

Dust storms and Chinese loess sources over the last 22 Ma

Atmospheric dust has a very important impact on global climate, but is not included in many climate models because of this establishing the source, flux, impact, controls and response of dust are pressing priorities. Current dust studies are mainly focused on the present but understanding its role in climate change requires looking back at long term archives. One of the most valuable climate archives is the Chinese Loess Plateau which covers an area of approximately 640,000 km2 and contains a 22 Myr record of dust deposition and climate proxies so is an ideal area to study long term dust deposition. The deposition and diagenesis of the sediments within the Chinese Loess Plateau is closely linked to climate, especially wind speed, source production, changes in sediment capture and the hydrological cycle. The source of Chinese loess is not well understood and hence at present it is impossible to interpret variations in dust accumulation rates in terms of climate. This project (a collaboration with Thomas Stevens of Royal Holloway and Randy Parrish of the British Geological Survey) aims to use single grained analysis to:
  • Determine dust sources for loess in China over the past 22 Myr.
  • Calculate the relative flux derived from specific sources.
  • Constrain the extent and type of controls on past dust production in these sources.
  • Constrain the type of atmospheric systems responsible for past dust transport.

More details about the project can be found on the project website

Methods development

In-situ U-Th-He dating

We have developed a significantly simplified method for in-situ U-Th-He dating removing the need to know any absolute concentrations or ablation pit volumes. This is done by calculating the normalised U, Th, and He concentrations of a conventionally dated calibration standard from its measured Th/U ratio and known U-Th-He age, and scaling these concentrations to the raw U, Th, and He signals of the sample. The Th/U ratio of the standard can be determined from its measured 208Pb/206Pb ratio, removing the need to use NIST glass as a reference material.
Because the U-Th-He age equation is scale invariant, it does not matter if a mineral’s U, Th, and He contents are expressed as atomic abundances or concentrations. They can even be renormalised to unity and plotted on a ternary diagram (Vermeesch, 2010). To calculate a helium age, it is not necessary to know the absolute concentrations of U, Th, and He. It suffices that two elemental ratios are known, such as U/He and Th/He, or U/Th and U/He. This insight forms the basis of the simplified method, which does not require knowledge of any absolute abundances or concentrations, but instead uses the raw mass spectrometer measurements.

Fission tracks

Three decades after the development of the zeta calibration method in our lab, the LGC is still pushing the envelope in fission track geochronology. Recent methodological advances include the first ICP-MS based fission track ages (Hasebe et al., 2004), and molecular dynamics studies of fission track formation.
Output of a method-based study investigating how fission tracks form and behave within the crystal structure of apatite
Output of a method-based study investigating how fission tracks form and behave within the crystal structure of apatite