My research centres on the Rising Star cave system, in the Cradle of Humankind World Heritage area, where a new species of hominin, Homo Naledi, was recently discovered by a group of recreational cavers. A research team has been assembled to constrain the age of these fossils, but also to place them in context and answer pressing questions, such as:
How the bodies came to be in the dark zone and within a chamber that is so difficult to access today?
Was there an alternate entrance in the past and If so, where was it?
Was H. naledi sheltering in the cave system?
The specific focus of my research project is the speleothems within various parts of the cave system, whose laminae preserve important plaeoclimatic and paleomagnetic information.
The ratio of stable isotopes of Carbon and Oxygen provide insight into environmental parameters at the time a given layer of calcium carbonate was formed. The ratio of C13 to C14 allows us to estimate the proportion of C3 vs. C4 vegetation at the surface i.e. woody or grassland, which can have evolutionary implications. The oxygen isotope ratios can be used to estimate the paleotemperature and other aspects of climate, depending on site-specific sensitivity.
Speleothems are also excellent recorders of magnetic excursions and reversals, being free of diagenetic effects. We can thus measure the orientations of the remanence that is preserved within the laminae to produce a record of magnetic change. This can potentially be calibrated using the Geomagnetic Instability Time scale (GITS) in order to constrain the age at certain points and confirm ages obtained from U/Th techniques. I plan to use a number of flow stones sampled from within Rising Star cave system to constrain both the age of certain events and the paleoenvironment surrounding the cave at the time of Homo Naledi.
Sedimentary Geology Research Group James Cook University Townsville, Australia