Ross Anderson

Advisor: Derek Briggs


Life on Earth traces back some 3.5 billion years, yet during its early history diversity was confined to two of the three major branches: bacteria and archaea. It is only in rocks from the last ~1,600 million years that vestiges of organisms with a membrane-bounded cell nucleus, the eukaryotes, can be found. Within this ~1,600 million year record we can observe two major diversifications: that of the crown group eukaryotes in the Neoproterozoic Era (1000-541 Ma) and that of metazoans in the Cambrian Period (541-485 Ma). Both these diversification events are accompanied by pronounced perturbations in Earth’s environment. Over the last few decades paleontologists have populated the records of these diversification events with new fossil discoveries to such an extent that workers are beginning to draw correlations between diversity and environmental change. Yet our knowledge of the preservation processes (taphonomy) affecting early eukaryotes and metazoans remains enigmatic. Consequently our ability to draw accurate temporal correlations is compromised; the absence of an organism in the fossil record at a particular time could be because it really did not exist, or because it has a very low preservation potential.

A better understanding of the preservational biases of the early fossil record of eukaryotes offers the prospect of distinguishing between these two fundamental causes of changing apparent fossil diversity thus improving our understanding of early eukaryotic evolution and its association with environmental change. Such an improved understanding of relationships between evolution and environment will provide important context to our search for habitable environments for eukaryotes on other planets. However, understanding the preservational biases of the eukaryotic record is not just important to our knowledge of early evolution. Biostratigraphy is a standard tool for defining divisions of geologic time and correlating rocks. Yet its application to Proterozoic and Early Cambrian time has proved problematic. A lack of knowledge of preservational biases means we cannot readily distinguish actual temporal range of organisms from their taphonomic range. Consequently research into the taphonomy of these groups is fundamental to creating a biostratigraphic framework for this interval of geologic time.

We will use the facilities at YCEO to interpret high resolution mosaic images of petrographic thin-sections of Neoproterozoic and Cambrian rocks that yield microfossils. Describing fossil assemblages in petrogrpahic thin-section enables them to be placed in their environmental context and as such will offer insights into preservation. YCEO has the facilities to enable the use of this technique. Image sizes generated are on the order of 12Gb and so other computing facilities are hardware limited.