Advanced analytical techniques for studying the morphology and chemistry of Proterozoic microfossils

Abstract

This paper outlines the suite of advanced multi-scalar techniques currently available in the toolkit of the modern Proterozoic palaeobiologist. These include non-intrusive and nondestructive optical, laser and X-ray techniques, plus more destructive ion beam and electron beam methods. Together, these provide morphological, mineralogical and biochemical data at flexible spatial scales from that of an individual atom to the largest Proterozoic microfossils. An overview is given of each technique and a case study from the exceptionally well-preserved Torridonian biota of NW Scotland is presented. This microfossil assemblage was first recognized over a century ago, but its great diversity and evolutionary importance has only recently come to light, due in no small part to the research efforts of Martin Brasier.

GGR Biennial Critical Review: Analytical Developments Since 2014

“…The same authors also recently published a review of NanoSIMS applications for studying microfossils (Wacey et al . ).…”

“…Chemical zoning of organic carbon and nitrogen also revealed framboid morphology inside larger pyrite grains. The same authors also recently published a review of NanoSIMS applications for studying microfossils (Wacey et al 2017).…”

A New Frontier for Palaeobiology: Earth's Vast Deep Biosphere

“…This challenge is twofold. First, new microanalytical techniques can and should be used to test whether microstructures of interest have the physical and chemical characteristics expected of bona fide fossils (see Wacey et al for a recent review of such methods). For example, focused ion beam transmission electron microscopy (FIB‐TEM) provides a means to investigate the internal architecture and elemental composition of submicron‐thick slices through microstructures of interest.…”

“…SIMS and ToF‐SIMS techniques can additionally detect hydrocarbon moeties, nitrogen, phosphorus, and sulfur, and determine their stable isotope compositions, and in the case of nanoSIMS, map them at very high spatial resolution. X‐ray spectroscopic techniques can probe the composition and coordination chemistry of organic and inorganic materials making up individual microstructures, revealing (for example) the presence of particular organic functional groups . The second way to address the biogenicity challenge is to extend the experimental exploration of abiotic processes of mineral morphogenesis, particularly those that might generate metalliferous microscopic filaments.…”

Contributions of Professor Martin Brasier to the study of early life, stratigraphy and biogeochemistry

“…Critical re-analysis of the Apex microtextures by Martin and colleagues ( Fig. 1) followed three main strands: (1) investigation of the geological context of the Apex Chert, particularly the relation of the black organic dyke cherts that hosted the 'microfossils' with the stratiform seafloor cherts (Brasier et al 2011a); (2) detailed petrographic mapping and investigation of the chert fabrics that hosted the 'microfossils', involving the development of automontage imaging techniques (Brasier et al 2005); and (3) study of the crystallinity and distribution of the organic matter using laser Raman spectroscopy and, subsequently, other analytical techniques such as focused ion beam transmission electron microscopy and laser confocal scanning microscopy Wacey et al 2016a). This work culminated in the publication of the paper 'Questioning the evidence for Earth's oldest fossils' (Brasier et al 2002), which was a landmark paper that stimulated much controversy surrounding the oldest reliable fossil evidence for life on Earth (Schopf et al 2002;Schopf & Kudryavtsev 2013).…”