Overview

Project Highlights:

  • Develop Miocene isotopic proxy records of rainfall that track the Asian Monsoon system.
  • Be at the forefront of cutting edge palaeoclimate and geochemical proxy research.
  • Gain experience with state of the art mass spectrometric techniques.
  • Engage with the Ocean Drilling Programme (ODP), travel to international core repositories.

 

Overview:

This project will reconstruct rainfall amounts by using state of the art proxies and will contribute to or understanding of the global climate system. The Late Miocene is a period of great interest for the study of long term climate change. During this period, the earth gradually cooled and eventually gave rise to the Quaternary period characterised by orbitally-forced episodes of ice ages. Climatic conditions that were initiated in the Late Miocene period ultimately gave rise to modern ecosystems (Herbert et al. 2016) and enabled the evolution of the human species. But global temperatures were warmer than today, so this offers an opportunity to study the earth’s climate under these conditions. Today, the tropics play a key role in the hydrological cycle and the regulation of the earth’s climate. In Asia the monsoon is an important feature of the hydrological cycle and climate. The Asian Monsoon is thought to have evolved during the Miocene and recent evidence has shown that during the Late Miocene, the Asian Monsoon intensified as a result of the uplift of the Tibetan plateau (e.g. Holbourn et al. 2018). In addition, the Asian monsoon is a sensitive to climate change as it has significantly varied in strength during the Quaternary period. Most focus has been on reconstructing climate from oceanic proxies, but new evidence of river incision suggest continental rainfall increased significantly (e.g. Nie et al. 2018). However, without a direct rainfall proxy it is hard to differentiate rainfall from tectonic uplift, and we know very little about the actual Miocene rainfall regimes.

At low latitudes it has been demonstrated that the primary control on hydrogen isotopes in rainfall is an amount effect (Niedermeyer et al, 2016). For this project we will, therefore, aim to reconstruct rainfall amounts as recorded by hydrogen isotopes. Hydrogen isotope ratios are preserved in leaf waxes from terrestrial vegetation and form a 20 Ma long archive in marine sediments of the South China Sea (Zhou et al, 2017). These offer a unique opportunity to study past continental rainfall regimes. Combining proxy data with an analysis of sedimentological, geochemical and physical property data will provide a context for understanding the depositional system.

Figure 1: Precipipitation of the June, July, August summer months showing features of the Asian Monsoon system . The Bengal Fan and the South China Sea contain a series of available records rich in terrestrial sediments that span the last 20 Million years.

Methodology

The region of the Asian monsoon is shown in Figure 1. A series of ODP/IODP sites will be strategically chosen from the Bay of Bengal and the South China Sea to capture the main features of the Continental Asian Monsoon system. For this project in particular, hydrogen isotopes of preserved leafwax will be used to track rainfall regimes from the continent. In the tropics, the Hydrogen isotopic signal in leafwax reflects the amount of rainfall. Sediment samples from selected sites will be extracted in the laboratory using automated solvent extraction (ASE350). Extracts containing leafwaxes will be examined using GC/MS and stable isotopic ratios (d13C and dD) of individual compounds will be determined using a Thermo Delta V plus irm-GC/Ms system. The School is further equipped with state of the art ICP/MS and XRF equipment for further geochemical analysis.

Training and Skills

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.   In addition the student will receive training in organic geochemical techniques e.g. mass spectrometry with an emphasis on stable isotopes. The student will join a thriving community of geologists and palaeoclimatologists at University of Leicester. Training of presentation skills is envisaged by participation at major international conferences.

Timeline

Year 1: Development of research proposal; identification of sites (inclusing IODP/ODP); applying for samples, collecting samples; training in laboratory techniques and initial analysis.

Year 2: Data collection and analysis, conference presentation.

Year 3: Data analysis; writing up (ideally resulting in a peer reviewed journal articles).

Partners and collaboration (including CASE)

Dr Arnoud Boom leads research on stable isotopes as proxies for palaeoclimate. Prof. Sarah Davies is a clastic sedimentologist, whose research seeks to understand the processes that controlled deposition and erosion in non-marine and shallow-marine settings preserved in the geological record. She leads the European Petrophysics Consortium for the International Ocean Discovery Program (IODP). Dr Mike Norry is a geochemist with particular interest in the paleo-environment of mudstones.

Further Details

Contact: Arnoud Boom (ab269@le.ac.uk)