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C409: Unlocking the sediment archive of carbon consumption by chemical weathering from the Mekong River in SE Asia (Lead Supervisor: Ed Tipper, Earth Sciences)

Supervisors: Ed Tipper (Earth Sciences) and David Hodell (Earth Sciences

Importance of the area of research:

Chemical weathering regulates Earth's carbon cycle and hence global climate over geological timescales. Ca and Mg from silicate minerals are released to the solute phase during chemical weathering . This solute Ca and Mg subsequently gets buried as Ca and Mg carbonates in ocean basins transferring carbon from the atmosphere to the carbonate rock reservoir providing the climatic feedback that has maintained Earth's climate equable over geological history.    A key record of this is provided by the clays that are present as detrital sediments in large river systems.   The Mekong Basin in SE Asia from its headwaters on the Tibetan Plateau spans China, Laos, Thailand Cambodia and Vietnam.  It is one of the largest in the world, a hot-spot for carbon transfer and will act as a case study for this research.

Project summary:

This project will involve a dedicated research expedition to the Mekong River Basin in SE Asia to add to our already large collection of sediments and waters from the region.  A  combination of state-of-the-art techniques will be used to pick apart the archive of weathering that is recorded by river sediment.  By combining mineralogy and geochemistry it is possible to decipher the geochemical signatures that are held within different parts of secondary minerals, especially clays.  Here, we will target oxygen and hydrogen and lithium isotopes in clays to quantify when, and where the sediments at the mouth of Mekong formed.  This will tell us where  in the basin the key areas for carbon transfer by chemical weathering occur.

What the student will do:

The project will involve major components of both field and lab work.  The student will work in the isotope geochemistry and Godwin labs for palaeoclimate, with hands on day to usage of the mass spectrometers coupled with expert training in all the techniques required to make an isotope ratio measurement. The student will begin by measuring samples from our archive sediment sample collection from the Mekong River basin before collecting dedicated samples.

Key questions are:

1)Where does the weathering take place?

2)When does the weathering take place?

3)What controls the stable isotopic compositions of large river systems?

Please contact the lead supervisor directly for further information relating to what the successful applicant will be expected to do, training to be provided, and any specific educational background requirements.

References:

Dellinger, M., et al., Lithium isotopes in large rivers reveal the cannibalistic nature of modern continental weathering and erosion. EPSL, 401, 359-372 (2014)

Lupker, M., et al.  Increasing chemical weathering in the Himalayan system since the Last Glacial Maximum.  EPSL, 365, 243-252 (2013)

Yeh, H.,  & Eslinger, E.V.,  Oxygen  isotopes  and  the  extent  of  diagenesis  of  clay  minerals  during  sedimentation  and  burial  in  the  sea.  Clays and clay minerals, 34, 403-406 (1986)

Follow this link to find out about applying for this project.

Other projects available from the Lead Supervisor can be viewed here.

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