Diffraction and Spectroscopy of Marine Calcite Biominerals: Insights into Structure and Geochemistry
type: CreativeWork
description: Anthropogenic climate change is one of the biggest existential threats to the natural world and the place of humans within it. The key to understanding and shaping the future climate lies in exploring records of climate change through Earth's history. Some of our best records of climate over the past 65 million years are based on chemical information stored in the calcite biominerals produced by marine organisms. Organisms such as foraminifera and coccolithophores provide an unparalleled 'proxy’ archive of past marine conditions. The way in which these organisms record these proxy archives is largely unknown, and is a fundamental question in applying and interpreting palaeoclimate proxies. In this thesis, I apply diffraction and spectroscopic methods to study the structure and chemistry of calcite biominerals, to assess how these structures acquire and record these proxy signals. Understanding these processes is vital to testing the fidelity of palaeoproxies and the interpretations that can be drawn. In Chapter 2 I develop a toolbox for the analysis of electron backscatter diffraction (EBSD) data collected on calcite biominerals. The toolbox is presented in a tutorial format on a section of the foraminifera Orbulina universa. In Chapter 3 I apply this toolbox to a range of foraminifera to explore the micron (µm)-scale differences in the structure and biomineralisation of these calcitic organisms. I explore the structural differences between biologically controlled and biologically induced calcite formation, and present a model for multi-scale hierarchical templating in calcite biomineralisation of foraminifera. In Chapter 4 I investigate the chemical coordination and sub-µm scale distribution of Na in the benthic foraminifera Amphistegina lessonii using scanning transmission X-ray microscopy (STXM). Na in the test of A. lessonii is incorporated in a spatially heterogeneous manner, showing banding in a mode comparable to that seen previously for B and Mg. The near ed…
abstract: Anthropogenic climate change is one of the biggest existential threats to the natural world and the place of humans within it. The key to understanding and shaping the future climate lies in exploring records of climate change through Earth's history. Some of our best records of climate over the past 65 million years are based on chemical information stored in the calcite biominerals produced by marine organisms. Organisms such as foraminifera and coccolithophores provide an unparalleled 'proxy’ archive of past marine conditions. The way in which these organisms record these proxy archives is largely unknown, and is a fundamental question in applying and interpreting palaeoclimate proxies. In this thesis, I apply diffraction and spectroscopic methods to study the structure and chemistry of calcite biominerals, to assess how these structures acquire and record these proxy signals. Understanding these processes is vital to testing the fidelity of palaeoproxies and the interpretations that can be drawn. In Chapter 2 I develop a toolbox for the analysis of electron backscatter diffraction (EBSD) data collected on calcite biominerals. The toolbox is presented in a tutorial format on a section of the foraminifera Orbulina universa. In Chapter 3 I apply this toolbox to a range of foraminifera to explore the micron (µm)-scale differences in the structure and biomineralisation of these calcitic organisms. I explore the structural differences between biologically controlled and biologically induced calcite formation, and present a model for multi-scale hierarchical templating in calcite biomineralisation of foraminifera. In Chapter 4 I investigate the chemical coordination and sub-µm scale distribution of Na in the benthic foraminifera Amphistegina lessonii using scanning transmission X-ray microscopy (STXM). Na in the test of A. lessonii is incorporated in a spatially heterogeneous manner, showing banding in a mode comparable to that seen previously for B and Mg. The near ed…
author: Read, Elizabeth
language: eng
keywords: foraminifera, proxy, calcite, STXM, NEXAFS, ptychography
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/2e71f24d-0fc4-4b8d-bce6-ca905276a27e/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2019-07-18
date modified: 2026-07-22T22:24:06Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.54485