Thesis Format
Alternative Format
Degree
Master of Science
Program
Geology
Supervisor
Blamey, Nigel.
Abstract
The Paleozoic (500-300 million years) was a dynamic era in Earth’s history characterized by environmental diversity and multiple extinction events. Understanding climate change throughout the Paleozoic not only allows for paleoclimate reconstruction but offers a glimpse into how life has progressed through time. By studying oxygen, one of the most important facets of any climate, the fluctuation of oxygen and its link to rises and declines of life throughout the Paleozoic may be studied. Halite offers a unique approach to studying the facets of Earth’s past temperatures due to its ability to form fluid inclusions, which can be studied using microthermometry to measure actual formation temperatures during halite crystallization at the brine-surface interface. This study aims to utilize halite-hosted fluid inclusions that contain trapped air bubbles to determine the atmospheric concentration of oxygen and Paleozoic temperatures at which the halite precipitated, as well as chemical characteristics in each area that the halite precipitated. This study utilizes multiple methodologies, including cutting-edge gas analysis to directly measure the atmospheric gases trapped in fluid inclusions, microthermometry and trace chemistry.
Using halite dated to the Cambrian, Silurian and Permian from various areas, respectively Australia, Canada and the United States allows for a detailed understanding of their environmental conditions during halite crystallization, by determining surface atmospheric air composition, temperature at halite formation and trace chemical characteristics of the halite and surrounding strata. Atmospheric oxygen concentrations ranged throughout the Paleozoic and changed when approaching or following extinction events. In the late Cambrian, O2 levels were around 11.60% (± 1.04). In the Silurian, an environmentally stable period, O2 increased to 16.23% (± 1.04), closer to modern atmospheric levels of ~ 21%. The Permian, a period of extinction events, saw the beginning of a decrease in O2 content, from 16.05% (± 1.04) in the Leonardian stage (280 Ma), before dropping to 10.08% (± 1.04) O2 in the Guadalupian stage (260 Ma) as the end-Guadalupian extinction occurred. These results provide insight on the fluctuations of both surface temperatures and atmospheric oxygen levels.
Summary for Lay Audience
The Paleozoic Era, which occurred from 541 to 252 million years ago, was a time of great change. Extinction events where many species of plants and animals died, hot temperatures around the world and the growth and evolution of animals all occurred during this time. By studying the change in climates throughout the Paleozoic, the information gained can aid in providing insight into current and future climates. The issue in studying ancient climates is the lack of material that represents these climates, which is why fluid inclusions were used to study Paleozoic climates. Fluid inclusions are essentially tiny bubbles within minerals, made of the fluid that the mineral formed from. Halite, or rock salt, contains many fluid inclusions as well as air bubbles trapped within the fluid, similar to air bubbles within ice cubes. Since halite forms at the surface of brines, or salty waters like seawater, the atmospheric air at the water surface becomes trapped during halite crystallization. A number of methods were used to determine the chemical composition of the halite, the composition of the atmospheric air trapped within the fluid inclusions and the temperature which the halite formed at.
Halite samples from three different time periods within the Paleozoic, the Cambrian, Silurian and Permian were chosen, from Australia, Canada and the United States. The Permian period was separated into two stages of the Permian, the Leonardian and Guadalupian. The different locations and time periods allow for a better representation of ancient atmospheric oxygen and provide insight into climate changes throughout the Paleozoic. After conducting analyses, atmospheric oxygen showed change that coincides with the beginning and end of extinctions. Cambrian oxygen was 11.60%, Silurian oxygen was 16.23%, the Leonardian stage was 16.05%, and the Guadalupian stage was 10.08%, which is much lower than modern atmospheric oxygen, which sits around 21%.
Recommended Citation
Oelschlagel, Matthew, "Ancient Oxygen Levels of Paleozoic Fluid Inclusions" (2025). Electronic Thesis and Dissertation Repository. 10695.
https://ir.lib.uwo.ca/etd/10695
