We think we found a fossil site – now what?

When we locate a potential site locality, we begin a process of exploration and evaluation to determine whether there is potential for further research at that locality. Our basic tools are a handheld GPS, a rock hammer, and a panga (or machete).

Field crew, 2nd trip: Andy with the GPS, Morris with the rock hammer, Kevin with the machete: Did the timer go off? is the camera working? did anyone hear a ‘click’?

The main objective of our project is to locate historic mining sites, and to evaluate whether they contain deposits and other features that are useful to us as palaeoanthropologists. We are looking for a variety of in situ (i.e., undisturbed) deposits including:

  • speleothem or cave formations, which can be sampled to obtain geological dates, and for stable isotopes which tell us about past climatic and environmental conditions;
  • cave infill sediments (derived from soil and other debris from both outside and inside the cave), which can tell us how the cave filled in, and also may contain evidence of the outside environment such as pollen;
  • fossil bone, including those of reptiles, birds, and rodents, as well as of larger animals including bovids, carnivores, primates, and of course, our own ancestors (hominids).

For some sites, the presence of such evidence can be quite obvious, especially if there are dense fossil deposits just waiting to be excavated. However, at other sites, it can take considerable effort to determine whether this evidence is present. Some sites are small and the deposits easily located, and others – especially when the mining activity was extensive – can be complex and more difficult to define.

One of the underlying objectives of this project is to consider what evidence at such sites can be used to answer questions of interest to palaeoanthropologists even in the absence of fossils. After all, when we find fossils (and especially those of hominids), we then use a battery of sampling techniques such as those above to obtain information about the temporal, environmental, and depositional context of that fossil. But since fossils are relatively rare in the geological record, we may be missing out on valuable information about past environmental conditions by passing over deposits in which hominid or other fossils are rare or even absent. This information could help us to refine our models about environmental and adaptive change during hominid evolution.

So, after that extensive preamble, what do we do when we think we have located a site? There are three basic tasks to complete: defining the limits and features of the site; mapping the locality; and evaluating the site’s potential for future research.

Defining the limits of the site involves exploration of the site’s geographical and geological features. We walk up and down hills, climb rock outcrops, and (carefully!) climb into mine shafts and trenches, looking for speleothem deposits, breccia and cave infill sediments, and fossils.

A miner’s trench exposing a lot of geological formation: Can anyone see any breccia up there?

One of the challenges in this work is being able to see the ground clearly in order to find features, breccias blocks, and of course, fossils. This is where the panga comes in handy!

Like most arid regions, many of the plants here have thorns. This site is overgrown with acacia trees and brambles. Keep repeating to self: ‘This is better than being stuck behind my desk at the universiity!’ (There is actually a nice cave infill deposit in this view… just to the right of the machete!)

The miner’s dumps are a great source of information about the deposits on the site. We comb the hills of rock, searching for fossils and other evidence of the nature of the underground deposits. Depending on what we find, we then have to search the mine trenches and chambers to determine where the blocks in the dump came from.

Fossils can be difficult to ID in the field. Observe the fossil braincase (below the knife to the right), and a vertebra (to the right on the edge of the block) of un-named mammals in this breccia block.

Finally, all of the features of the site are mapped using the handheld GPS, which locates each data point taken to within approximately 5 meters. For our initial fieldwork survey, this is good enough, but if we were to return for sampling or excavation we would use total station survey equipment and map the site with more accuracy.

Andy enters data points on the Trimble GPS at a small locality near Gondolin, North West Province.

The initial survey and exploration of a new locality can take several days, and also includes extensive photographic and written documentation; we also record information about the site on databases on the handheld GPS and a table PC. The final task is to sit in the shade and discuss what we have observed on site, and evaluate the potential for further work in the form of sampling or excavation.

Once we have completed this process of site survey and evaluation, we go back to the maps, head out to a new area, and begin the process again. All in a day’s work!

– KL Kuykendall

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