Overview

Project Highlights:

  • Study a set of unique tropical coral cores covering up to 430 years of ocean climate history from Australia’s iconic Great Barrier Reef to reveal the onset of the Anthropocene in the tropical Pacific Ocean
  • Carry out research with cutting edge multiple isotope and trace element geochemistry with national and international partners
  • Contribute to a multi-disciplinary international research effort to define the ‘Golden Spike’ for the Anthropocene with society-relevant implications of research outputs

Many geo-ecosystems around the world are increasingly modified by Humans. Coral Reefs are no exception. Geologists are currently debating the formalisation of the term Anthropocene as a new chronostratigraphic geological unit. The selection of a Global Boundary Stratotype Section and Point (GSSP) candidate section for the Anthropocene is a requirement in seeking formalisation of the term as a potential new unit of the International Chronostratigraphic Chart. Currently, the GSSP candidate sites and archives are chosen by an international working group that will strive to provide compelling evidence for a transition from the Holocene to the Anthropocene. All sections will be in borehole/drill cores, most showing annually resolved laminations that can be independently dated radiometrically to confirm a complete succession extending back to pre-Industrial times. Airborne signals provide the most geographically widespread and near-isochronous proxies, applicable across most of these environments, which are expected to provide distinctive markers at around the mid-20th century, the preferred start/base of the Anthropocene. The question arises if coral reefs provide clear Anthropocene markers which set them apart from previous reef development stages in Earth history.

Coral skeletal proxy archives are a prime GSSP boundary candidate from the tropical oceans due to their yearly growth banding providing highly precise age control over several centuries locking a suite of geochemical information into their skeleton (Waters et al., 2018; Hennekamet al., 2018). Corals have been shown to record climatic and environmental change over several decades to centuries related to natural processes. Furthermore, coral provide invaluable records of anthropogenic activity, e.g. CO2 uptake by the oceans (Suess effect; Swart et al., 2010), radiocarbon bomb spikes, radionuclide distributions, heavy metal discharge and eutrophication (Lee et al., 2014). All this makes corals a key GSSP candidate from the oceans to define the start of the Anthropocene.

Location of GBR coral core site (Britomart Reef) selected for the Anthropocene project. Right) X-ray positive print of a core top with sampling transect. Note the yearly growth banding analogue to tree rings which make corals the key biogeological-archive from the tropical oceans. Inset shows carbon isotope record from nearby Flinders reef and other coral reefs recording the rapid increased in fossil carbon uptake by the oceans since 1950 (from Pelejero et al., 2005; orange bar indicates potential time window for GSSP definition). Map made in Google Earth.

Methodology

The coral cores from the Great Barrier Reef (GBR) were obtained in 2017 and 1987 by the Australian Institute of Marine Science (AIMS, Australia) covering 430 years of coral growth. The cores will be subsampled in the coral palaeoclimatology lab of Prof. Zinke and at partners labs at AIMS (Australia). Splits of carbonate powder samples will analysed at geochemical laboratories in Leicester and other UK (University College London, University of Southampton) and international partner laboratories (ETH Zurich, Max Planck Institute Mainz) to conduct specific geochemical analysis (14C, Pu, d15N, Boron isotopes, SCP’s). At Leicester, cores will be analysed for trace element/Ca composition, oxygen and carbon isotopes and to reconstruct sea surface temperatures, the hydrological cycle and atmospheric pollution (Hennekam et al., 2018). Lead isotopes will be analysed at British Geological Survey to reconstruct sources of lead pollution.

Training and Skills

The student will become proficient in experimental design and protocols, in use of sophisticated analytical equipment including inductively coupled mass spectrometry, stable isotopes, XRD, X-ray and CT-scanning (most at University of Leicester). This combination of innovative methods and state-of-the-art analytical equipment will provide you with a truly unique set of skills that will be attractive to both industrial and academic employers.

Timeline

Year 1: Get acquainted with the research methods and corals as climate archives through intensive literature study. Determine the sampling strategy for the long cores based on X-ray and UV-imaging provided by Australian colleagues (AIMS). Use of milling machine to obtain powders from the first long core. Check core parts for diagenesis with XRD and thin sections. Perform test measurements in stable isotope and ICP-MS labs before starting with real samples. Commence analysis of first real samples end of year 1. Organise water sampling with AIMS colleagues to characterize present-day seawater values of nitrogen isotopes, P/Ca and Pb isotopes for calibration of geochemical signatures during field campaign.

Year Continue the sampling and geochemical data acquisition on core 1 and start with core 2 and core 3. Collect instrumental climate data and perform initial correlation/regression analysis with climate indices to check for climate relationships in the 20th/21st century. Get aquainted with data analysis toolkits (R, Matlab, climate explorer). Aim for first presentation of initial data at national or international conference mid-end year 2.

Year 3: Application of data analysis toolkits to entire dataset. Interpretation of geochemical data and working out climate and environmental drivers at regional and global scale. Synthesis of data for best Anthropocene time markers. Publication of papers and conference presentations, including the opportunity to present at international meetings, will be part of the schedule from year 2 onwards.

 

Partners and collaboration (including CASE)

This student will work under supervision of Professor Jens Zinke, an expert in coral paleoclimatology and geochemistry, and co-supervision by Dr. Tiffany Barry who leads the ICP-MS laboratory at UOL. Dr. Arnoud Boom, an expert in stable isotope mass spectrometry and its application to tropical archives, will collaborate. Prof. Jane Evans at NEIF, BGS will support the lead isotope analysis. Dr. Janice Lough and Dr. Neal Cantin (Australian Institute of Marine Science), both world-famous coral core growth experts, will support coral coring, sampling and getting involved in publishing. International analytical exchange and fieldwork is envisaged with partner laboratories at UCL London, NOC Southampton and ETH Zurich.

Further Details

Contact: Prof. Jens Zinke, Centre for Palaeobiology, University of Leicester, jz262@le.ac.uk