Unlocking the potential of fossil charcoal: The use of Synchrotron Radiation X-ray Tomographic Microscopy

Fossil charcoal is abundant in the fossil record from the late Silurian onwards. It can provide information not only on the occurrence of wildfire but also on atmospheric oxygen levels. Understanding the role of fire in the ecology of vegetation and also in its role in the evolution of plant groups as well as communities and biomes necessitates the botanical identification of the charcoal. Charcoal preserves not only morphology but also anatomy of the plant organs. Scanning Electron Microscopy (SEM) provides an excellent way to study charcoalified plant organs but anatomical information often requires destructive sectioning. To overcome limitations of data collection from such fossils, which may be only a few millimetres in all dimensions, we have used a combination of SEM and Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM) to study the fossils, utilising the Materials Science and TOMCAT beamlines at the Swiss Light Source. This technique has not only revealed the internal structure of the fossils, but has also allowed three-dimensional reconstructions that permit digital dissection, allowing a much deeper understanding of their anatomy. Here we present data from a range of charcoalified plant organs including charcoalified pteridosperm pollen organs, ovules and cupules have been recovered from Mid Mississippian (Late Viséan) limestones from Kingswood, Scotland.