School of Earth and Environment

The Earth Surface Science Institute (ESSI) PhD Projects

Changes in Ocean Oxygenation During the Palaeocene-Eocene Thermal Maximum

Dr Robert Newton, Dr Simon Poulton (Newcastle University) and Dr Christian März (Newcastle University)

Background

The Palaeocene-Eocene Thermal Maximum (PETM) has become probably the best constrained example of rapid CO2 release and associated climate change in the geological record and has received a lot of attention as an analogue of future anthropogenic change. Most of the research to date has focused on questions concerning the source, magnitude, rate and timing of CO2 release and the profound changes this produced on climate, ocean chemistry and other parts of the Earth system (e.g. Higgins and Schrag, 2006; Panchuk et al., 2008; Zachos et al., 2005). An underexplored aspect of the PETM is the record of changes in the redox chemistry of the oceans. This has important implications for the understanding of nutrient cycling and is closely linked to the global cycles of sulphur and carbon during the event.

There are a number of tantalizing indications that marine oxygen depletion was common during the PETM, including enrichments of uranium and manganese depletion in the deep Atlantic (Chun et al., 2010); the development of laminated sediments, presence of redox-sensitive biomarkers and trace metals and/or organic matter/pyrite enrichments in the Arctic ocean and some epeiric sea sections (e.g. Dupuis et al., 2003; Dypvik et al., 2011; Gavrilov et al., 1997; Sluijs et al., 2006); and changes in trace fossil characteristics in South Pacific intermediate water (Nicolo et al., 2010). These observations point to redox changes of varying magnitude, duration and intensity, but are not easily comparable. This project will aim to produce a systematic survey of variations in marine oxygenation during the PETM from a range of palaeo-oceanographic settings, using tools commonly applied to the study of more ancient sediments, but whose application to this time period is sporadic or non-existent.

The cycling of phosphorus and nitrogen in marine waters is also strongly affected by redox conditions, with phosphorus, for example, being more easily returned to surface waters as oxygen levels decline (Algeo and Ingall, 2007). Nutrient interactions are important drivers of ecological changes, and create feedbacks on the regulation of oxygen concentrations in their own right, by exerting a control on surface water productivity.

Aims and objectives

This project will set out to characterize changes in ocean oxygenation during the PETM using Fe ratios (Poulton and Canfield, 2005; Raiswell and Canfield, 1998; Raiswell et al., 2001), framboid size distributions (Wignall and Newton, 1998), and trace metal concentrations (e.g. März et al., 2008), as well as characterizing interactions with the phosphorus, nitrogen, sulphur and carbon cycles. Samples have been sourced from a wide range of latitudes and oceanographic settings, including a high latitude suite of samples from Spitsbergen which represent an onshore-offshore transect. Specific objectives will be the generation of the following data sets:

  • Sediment Fe speciation and framboid size distributions to constrain changes in water column oxygenation
  • Trace metal concentrations will be used to further characterize water column oxygenation, and to examine water renewal times in sections with a limited connection to the open ocean.
  • Sediment P speciation and organic matter N isotope compositions will be investigated to determine the effects of redox changes on nutrient availability and possible feedbacks on productivity.
  • Carbonate associated sulfate and oxygen isotope compositions will be determined to document changes in the global sulphur cycle.
  • Supporting data such as total organic and inorganic carbon contents and isotopic compositions, XRD etc as necessary.

These data sets will then be compared with published sedimentological, palaeontological and geochemical data to document changes in ocean redox and the associated changes in nutrient cycling during the PETM.

Training

The project will provide an excellent grounding in a diverse range of geochemical and isotopic techniques with all necessary training being provided in either Leeds or Newcastle. The student will sit in the large Cohen Geochemistry and Palaeo research groups at Leeds, providing exposure to a broad range of expertise and ideas. The student will take part in the University of Leeds PhD training programme and will also attend the Urbino Summer School in Italy to learn new techniques and to network with other researchers.

References

Algeo,T.J. and Ingall, E., 2007. Sedimentary Corg:P ratios, paleocean ventilation, and Phanerozoic atmospheric pO2. Palaeogeography, Palaeoclimatology, Palaeoecology, 256: 130-155.

Chun, C.O.J., Delaney, M.L. and Zachos, J.C., 2010. Paleoredox changes across the Paleocene-Eocene thermal maximum, Walvis Ridge (ODP Sites 1262, 1263, and 1266): Evidence from Mn and U enrichment factors. Paleoceanography, 25(4): PA4202.

Dupuis, C. et al., 2003. The Dababiya Quarry Section: Lithostratigraphy, clay mineralogy, geochemistry and paleontology. Micropaleontology, 49(Suppl_1): 41-59.

Dypvik, H. et al., 2011. The Paleocene-Eocene thermal maximum (PETM) in Svalbard - clay mineral and geochemical signals. Palaeogeography, Palaeoclimatology, Palaeoecology, 302(3-4): 156-169.

Gavrilov, Y.O. et al., 1997. The Late Paleocene anoxic event in epicontinental sea of Peri-Tethys and formation of the Sapropelite Unit: sedimentology and geochemistry. Lithology and Mineral Resources, 32(5): 427-450.

Higgins, J.A. and Schrag, D.P., 2006. Beyond methane: Towards a theory for the Paleocene-Eocene Thermal Maximum. Earth and Planetary Science Letters, 245(3-4): 523-537.

März, C. et al., 2008. Redox sensitivity of P cycling during marine black shale formation: Dynamics of sulfidic and anoxic, non-sulfidic bottom waters. Geochimica et Cosmochimica Acta, 72(15): 3703-3717.

Nicolo, M.J., Dickens, G.R. and Hollis, C.J., 2010. South Pacific intermediate water oxygen depletion at the onset of the Paleocene-Eocene thermal maximum as depicted in New Zealand margin sections. Paleoceanography, 25(4): PA4210.

Panchuk, K., Ridgwell, A. and Kump, L.R., 2008. Sedimentary response to Paleocene-Eocene Thermal Maximum carbon release: A model-data comparison. Geology, 36(4): 315-318.

Poulton, S.W. and Canfield, D.E., 2005. Development of a sequential extraction procedure for iron: implications for iron partitioning in continentally derived particulates. Chemical Geology, 214(3-4): 209-221.

Raiswell, R. and Canfield, D.E., 1998. Sources of iron for pyrite formation in marine sediments. American Journal of Science, 298(3): 219-245.

Raiswell, R., Newton, R. and Wignall, P.B., 2001. A water column Anoxicity Indicator:  Resolution of biofacies variations in the Kimmeridge Clay (Upper Jurassic, UK). Journal of Sedimentary Research, 71(2): 286-294.

Sluijs, A. et al., 2006. Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum. Nature, 441(7093): 610-613.

Wignall, P.B. and Newton, R., 1998. Pyrite framboid diameter as a measure of oxygen deficiency in ancient mudrocks. American Journal of Science, 298(7): 537-552.

Zachos, J.C. et al., 2005. Rapid Acidification of the Ocean During the Paleocene-Eocene Thermal Maximum. Science, 308(5728): 1611-1615.