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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Understanding changes in Cenozoic carbonate chemistry

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One of the most enigmatic fluctuations in marine chemistry on geological timescales is the cyclic variation in the abundance of the dominant cations magnesium (Mg), calcium (Ca) and strontium (Sr) that have a major control upon the dominant form of calcium carbonate (CaCO3) precipitated - the oceans appear to regularly switch between ‘aragonite seas' and ‘calcite seas'. Determining the biological, environmental and tectonic processes responsible for these changes will significantly improve our understanding of the factors that control oceanic composition, as well better determine the impact of climate change on CaCO3 formation and preservation throughout the geological record.

The principal reactions governing carbonate precipitation in the oceans, and how this interacts with the marine Mg, Ca and Sr cycles. (Source: C.R. Pearce)
Ocean carbonate precipitation

Objectives

This project will provide new constraints on the processes that control the cation composition of the oceans, and establish how these mechanisms varied over the Cenozoic. The main objectives of this research are:

  1. To improve our understanding of the marine Mg, Ca and Sr    cycles using a non-traditional stable isotope approach.
  2. To better characterise cation incorporation into carbonates.
  3. To determine variations in the Mg, Ca and Sr stable isotopic composition of seawater over the Cenozoic to ascertain what caused the observed shift in Mg/Ca and Sr/Ca ratios.
Approach (Source: C.R. Pearce)
Approach (Source: C.R. Pearce)

Approach

δ26/24Mg, δ44/40Ca and δ88/86Sr records from inorganic CCVs will be used to determine how the cation isotopic composition of seawater has varied over the last 180 Ma. Combining the CCV isotopic and elemental records will enable changes in marine fluxes to be characterised in a manner not achievable using element ratios alone, as each isotopic system responds differently to marine processes. Computer modelling will be used to combine and interpret the results from each system.

Related Projects

Calcium carbonate veins as recorders of past ocean chemistry

Coupled change in global climate and the carbon cycle

Descent into the Icehouse

 

 

 

 

 

 

(Source: Coggon et al. 2010))
Seawater ratios

Key Contacts

Dr Christopher Pearce  

Prof. Damon Teagle  

Dr Gavin Foster  

Prof. Toby Tyrrell

 

 

 

Calcium carbonate veins formed in the ocean crust provide an inorganic record of Cenozoic seawater chemistry. (Source: IODP)
Calcium carbonate veins

Related Publications:

Pearce, C.R., Saldi, G.D., Schott, J., Oelkers, E.H. (2012), Geochim. Cosmochim. Acta, 92, 170-183

Coggon, R.M., Teagle, D.A.H., Smith-Duque, C.E., Alt, J.C., Cooper M.J. (2010), Science, 327, 114-117

PhDs and Other Opportunities

A PhD studentship investigating the Cenozoic biogenic carbonate record is currently being advertised. Please see here or contact Christopher Pearce for information.

For other opportunities visit GSNOCS

Associated research themes

Past Present and Future Environmental Change

Formation and Evolution of the Ocean Crust

Hydrothermal Processes and Mineral Deposits

Related research groups

Geochemistry
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