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

A little note on desktop mapping software

Previous posts have referred to some of the software we have been using on the project. So, we will explain a little bit about this software in a series of blogs dealing with the packages we use for different aspects of the project. The first of these is on ArcGIS and other PC based software we use for mapping.

ArcGIS is the main software package we use on the project, and particularly the ArcView and ArcCatalog components; we also make use of Quantum GIS (QGIS), GNU Manipulation Program (GIMP) and Google Earth.

An example of a project in ArcView showing  different sets of data (polygons of geological units) may be layered in their correct geographical position and displayed together.

As the project uses GIS to arrange and orient various kinds of data geographically, ArcView is the component we use the most. ArcView allows us to display different layers representing different types of data. It is crucial in planning and implementing the survey as it gives us access to all the relevant data for an area of interest and will allow us to analyse those data when the project has finished. These data (layers) consist of mine locations, geological formations, topographical maps etc.

In addition to ArcView, we have been using ArcCatalog to create blank shapefiles (A shapefile is a file format created by Environmental Systems Research Institute (ESRI) to store location data in vector format, i.e. polygons, polylines and points, along with attribute information). Point files are single locations and consist of X and Y, and sometimes Z, co-ordinates, along with space for any additional data we may want to record such as an observation or a type of feature. Polygon files consist of points and lines joining them together along with the information defining how they relate to each other. They are frequently used to record large features and because they are complete shapes, whether regular or irregular, once they have been drawn we can calculate the area they cover. This is particularly helpful when trying to determine the size of a site or a feature. We can also add relevant information to the polygon files in the same way that we can with point files.

We can also use ArcGIS to create a link between our maps and our database of sites. These sites can then be displayed in their geographical location with all the information we have recorded about them. This will be covered in more detail in a later blog post.

For map preparation, mainly cutting out relevant map features (e.g., the area of a geological formation) and changing the file format, we have been using the GNU Image Manipulation Program (GIMP) on a MacBook Pro, because the use of a mouse and a larger screen is much more effective than the pen and touch input on the tablet PC.

We have been using QGIS (a free, and highly recommended, GIS package) predominantly for converting file types. As it is an open source programme it offers a larger number of possible file extensions for conversion without the need for expensive extensions. This has proved especially beneficial with the final programme we use, Google Earth.

We have used Google Earth in a variety of ways. The shapefiles produced in ArcGIS for the geological formations and the mining locations have been converted to the .kml format that can be opened in Google Earth. This is extremely helpful when communicating with colleagues and other interested individuals who do not have access to a GIS package. Secondly it has assisted in pre-planning the areas to visit through zooming in close to the earth’s surface and establishing whether features of the lime mines we have plotted, and other relevant geography, can be visualised. It may also provide an excellent platform for further dissemination of results in the future.

Now that we have covered ArcGIS and our other mapping programs, the next blog in this series will tackle ArcPad.

– A Reid

On a brief little layover in Frankfurt…

There is a story about palaeoanthropology just about anywhere you might travel in the world. Our route to South Africa for the second fieldwork trip included what was to be a brief layover in Frankfurt, Germany, but which for me, became an unscheduled overnight stopover (more on this below).

Frankfurt is the home to the Senckenberg Research Institute and Natural History Museum, which is a prestigious research centre that includes in its diverse research programmes both fieldwork and laboratory research in palaeoanthropology. Senckenberg was once home to the distinguished German palaeoanthropologist G. H. R. von Koenigswald. During his career, which spanned from the 1930s to his death in 1982, von Koenigswald conducted research into human origins in many parts of the world. He recovered fossils now recognized as Homo erectus in Java, including the Modjokerto juvenile calvarium, and some of the very robust Sangiran material. In the 1950s, von Koenigswald visited South Africa to study the hominid fossils from sites such as Sterkfontein and Swartkrans, and later, he also published with the late South African palaeoanthropologist Phillip V. Tobias (…and thus, some links in this blog to our South African fieldwork project…).

Aside from his scientific pursuits, von Koenigswald lived through some incredible experiences. During World War II, he was taken prisoner (in Java) by the Japanese, and spent the war years in a POW camp. In fact, he was presumed dead by many, and as a result some of his fossil finds were initially described by Franz Weidenreich. After the war, the two great palaeoanthropologists resumed work together, and proposed that the taxa Pithecanthropus (named for the Javanese fossils) and Sinanthropus (named for the Chinese fossils) should be merged because of the similarities displayed by these two assemblages. Later, all such material was incorporated into Homo erectus, as it is now known.

Today, the Senckenberg Research Institute remains a world-renowned centre for palaeoanthropological research in Africa, Europe and Asia. Further information about their projects and researchers can be found here: http://www.senckenberg.de/root/index.php?page_id=898

Unfortunately, during my journey to South Africa, I was not able to visit the Senckenberg Institute or museum. Though we were only scheduled for about a 2 hour layover, I was not allowed to continue to South Africa by the customs officials at the Frankfurt Airport because I did not have any clean, blank pages in my passport! I was told that South Africa has a ‘very strict’ policy about this, and that I would have been turned me away on arrival in Johannesburg. So I spent the night in Frankfurt, and the next day visiting the US Embassy in order to obtain an insert of 10 clean, blank passport pages. (I just want to add that I did have five pages that appeared to have space for a customs stamp, but all had already been stamped at other ports-of-call).

The next day, everything was in order, and I was on my way to South Africa, a bit irritated over the delay, but still excited to get to the field. An expensive lesson in travel preparation, to be sure.

– KL Kuykendall

ps. Andy Reid made it all the way to Joburg as scheduled…!

Geology maps: where is that dolomite?

Apart from the two historic mining maps we have acquired, a substantial amount of our information has come from 1:250,000 maps of the bedrock geology. These provide the geological characteristics, and the location, of the underlying rocks in any area of South Africa. Because the types of caves we are looking for form in dolomite, locating areas where this rock is present is one of the main factors in determining our survey strategy.

The geology maps have been treated in the same way as the historic mining maps, utilising only the information relevant to the project and converting that information into a usable digital format. However, unlike the mining maps, on which the digital information is characterised by a point, the information we require from the geology maps relates to the region (including the size and shape) occupied by a lithological unit of bedrock.

Geology base map. An example section of a 1:250000 geological map showing areas of dolomite in different shades of blue (map published byDepartment of Mineral And Energy Affairs, Republic of South Africa 1981).

 

In order to convert this map information from Raster to Vector formats, we trace around the edges of the bedrock formations we are interested in, save them as a polygon (instead of a point), and then add the lithological information as an attribute of the feature. Not only does this kind of digitisation help in establishing areas to investigate but it also has a number of other advantages.

Geology map with polygons.  In this figure, the blue areas denoting a dolomitic lithological unit have been overlain by a traced polygon using ArcGIS and are now represented by different colours to indicate different attributes the rock unit might have, such as including interbedded chert, quartzite, or shale (map published byDepartment of Mineral And Energy Affairs, Republic of South Africa 1981).

The first advantage is the reduction in size of the file from a large scanned map which may be as much as 390 Megabytes per file to a few Kilobytes of data. This is helpful not only when trying to use the data on a handheld computer but also for storage on the device, since we can fit many more polygons than scanned maps on a 4 Gigabyte memory card. The second advantage of digitising in this way is that we can select the only data that are  relevant to the project and its aims. We can ignore all the other geological formations which do not hold the appropriate characteristics and only digitise those that we need. This again saves space on the memory cards but also saves time, both in the tracing of the geology and in locating regions appropriate to the project in the field.

Geology polygons. This figure shows how the digitisation of the geological formation looks when the area is loaded onto the handheld computers. The pink and orange colours represent the (dolomite) geology and the green background represents the Vector outline of the main provinces of South Africa.

The “Identify” function on the GIS software (ArcPad) we use on the hand-held computers can be used to call up the attributes of any of the Vector layers  once defined. The GPS function on the handheld also enables us to determine our current field position relative to the geological formations (polygons) and to the mines (points). This helps us to avoid spending a lot of time driving around searching in the field!

This is the final step in the digitisation process to prepare the maps for the field. The next blog in this series will deal with some of the hardware and software we are using in more detail.

– A Reid