Molecular and isotopic signatures of life surrounding the Neoproterozoic Snowball Earth events

Abstract

Life on Earth transitioned from being mainly dominated by bacteria prior to the Cryogenian Snowball Earth events (717a 635 Ma) to an ecosystem in which biologically more complex eukaryotes (e.g. Archaeplastida and Metazoa) where able to proliferate. Using lipid biomarker analyses combined with inorganic and isotopic geochemical techniques, this dissertation investigates the sedimentary rocks of the Chuar Group ( 750 Ma, Grand Canyon, USA) and Araras Group ( 635 Ma, Amazon Craton, Brazil), to gain a greater understanding about the environments and community compositions before and after the Cryogenian glaciations. This work shows how the ecosystem recovered after the Snowball Earth events and investigates the carbon isotopic relationship between bulk organic matter and individual hydrocarbons in the Proterozoic. Overall this work observes heterotrophic organisms played a significant role in the investigates Precambrian environments, highlighting their importance in ancient ecosystems.