Overview

The high latitudes are of critical importance for the regulation of global climate, oceanography and biogeochemical cycles both today and in the past. Yet, the history of these regions during past high CO2 intervals such as the early Paleogene (~34-66 million years ago, Ma) and Cretaceous (~66-145 Ma) is typically poorly known. This represents a fundamental gap in our understanding of how high-CO2 worlds operate and ultimately our ability to predict current and future anthropogenic change.

Sites drilled during International Ocean Discovery Program (IODP) Expedition 369 are ideally located to solve these issues as they recovered expanded sediments spanning the past ~160 million years of Earth history in the Indian Ocean off the SW coast of Australia. Over this same time interval, Australia separated from Antarctica and drifted northward. Hence, in the past, the core sites where situated at much higher southern latitudes. These new sediments cover the high-CO2 Paleogene and Cretaceous worlds when oceanographic circulation and the climate system were very different from today, e.g., the poles were >20°C warmer than today. There is increasing evidence that these ‘greenhouse’ worlds were very climatically dynamic and characterised by multiple short-lived intervals of environmental change and extinctions of marine organisms, e.g., abrupt global warming, changes in water column character/masses, and global ocean anoxia. One key issue that remains to be resolved is the relative impact of continental geography versus changing atmospheric carbon dioxide levels on global climate change. Specifically, did opening of the Tasman Gateway between Australia and Antarctica, permitting the development of the Antarctica Circumpolar Current, bring about the onset of a modern ocean circulation system and the end of the greenhouse world?

Ultimately this project will generate new data to directly address key outstanding questions regarding the mechanisms, feedbacks and consequences of tectonic changes at high southern latitudes providing crucial data against which to test Earth system models.

The IODP ship Joides Resolution coming into Hobart, Tasmania ready for IODP Exp. 369 (Top, credit: B. Huber). Bottom left: Deep-sea sediments recovered on IODP Exp. 369 and right: representative foraminiferal shells found in deep-sea sediments.

Methodology

This project will generate new high-temporal resolution records of (primarily) global climate, oceanography and carbon cycling across key hothouse intervals at International Ocean Discovery Program (IODP) sites from Exp. 369 in the Indian Ocean. This will include study of the character of peak greenhouse intervals in the Paleogene and/or Cretaceous, e.g., the Early Eocene Climatic Optimum (~50 Ma)/Cenomanian-Turonian (~90-100 Ma) and the dominant driver of subsequent global cooling from these states. These new highly expanded sediment sequences offer the opportunity to reconstruct these intervals of geological time at unprecedented resolution. This PhD project will involve detailed taxonomic, and geochemical (d13C and d18O, trace element records) study of foraminiferal tests preserved in deep-sea sediments to constrain a range of environmental parameters including: ocean temperatures, global ice volume and occurrence, ocean circulation patterns and carbonate chemistry (e.g., pH). These data will be supplemented with faunal and sediment analyses, e.g., scanning election microscopy, to determine foraminiferal shell preservation and %CaCO3 records to constrain deep ocean chemistry.

Training and Skills

CENTA students are required to complete 45 days training throughout their PhD including a 10-day placement. In the first year, students will be trained as a single cohort on environmental science, research methods and core skills. Throughout the PhD, training will progress from core skills sets to master classes specific to the student's projects and themes. 

The student will gain experience in processing sediment samples for micropalaeontological investigation and detailed training in foraminiferal taxonomy, and taphonomy. They will learn how to work in clean labs, generate and interpret carbon and oxygen stable isotope and trace element records from foraminiferal tests as well as a suite of other sedimentological/relevant geochemical proxies. The student will also develop skills in multivariate statistical techniques, graphing and mapping in the free R environment. These skills are highly transferable and will enable the student to progress in any STEM discipline, or specialise as a palaeontologist (in academia or industry) or palaeoceanographer.

 

Timeline

Year 1: Complete literature review. In parallel, receive training in laboratory protocols, sediment sample processing, and taxonomy of benthic and planktic foraminifera. Learn to use scanning electron microscope to evaluate foraminiferal test taphonomy (B’ham). Pick foraminifera from samples for stable isotope analyses (B’ham) and trace element analyses (OU). Visit to the Smithsonian, USA to work with Huber (Co-chief scientist on Exp. 369). Presentation at (provisionally) The Micropalaeontological Society Meeting, Switzerland (2019) or other as appropriate.

Year 2: Continue picking samples as necessary and generate bulk of geochemical and sedimentological data. Data interpretation and develop manuscript 1. Presentation of results at the IODP Exp. 369 science meeting in 2020 and international meeting such as International Conference on Paleoceanography, Sydney.

Year 3/4: Complete outstanding analytical work, data processing and interpretation. Prepare remaining manuscripts and thesis write-up. Presentation of final results, e.g., Climatic and Biotic Events of the Paleogene in 2020 or American Geophysical Union, San Francisco in 2021.

Further Details

Dr Kirsty Edgar - k.m.edgar@bham.ac.uk