Author Archives: moon0050

Getting to the bottom of things

This is about how a group of archaeologists dug some trenches. It began with a Flinders University field trip to Magpie Creek ruin, Sturt Gorge, South Australia and the aim of excavating the site to see what we could learn about it. We needed to dig six trenches. Digging a trench might sound easy; however, you need to know where to dig, how wide to dig, how deep to dig, and when to stop digging. First we consulted with Bob, our expert on where to dig holes. Bob selected six places within and outside the ruin where we were likely to uncover artefacts. Our trench sizes ranged from 1 x 1.5 metres to roughly 2 x 2 metres. That was a manageable size for a small team of three or four of us to dig, sieve, and record the changes in context, and the artefacts uncovered. First, we moved away the loose rocks on the surface, then we measured our trench and ran a string along the perimeter so we knew the boundary of the trench.


Excavation trench position marked out with string

Then came the digging. It started with a trowel. We poked with point, dragged and scraped along with the side of the trowel to remove the deposit. The idea is to remove the material quickly, but not to break up any artefacts, and to notice changes in the deposit, or context. These changes included changes to the composition, density and colour of the deposit that were indications that a change happened at that point.


The team from trench E busy excavating with trowel and shovel

Each time the context changed the details of the size, composition, PH and colour were recorded, together with details of any artefacts uncovered. Levels and the surface area of the new context were measured and recorded, and then this new context was excavated. This continued until the original, undisturbed soil surface or other structure was reached.


A new structure and context is reached. This image shows a brick floor uncovered by the excavation

Once the undisturbed natural soil, or a new feature, was reached we had hit the bottom. At square ‘A’ shown in the image above, most of the excavation involved removing a built up deposit that had resulted from the collapse of the walls. Once the deposit was removed a brick floor was uncovered inside the building, together with an adjoining floor composed of plaster and soil. This was the only area of the building that had a brick floor. The use of this substantial floor material is an indication that it was an important area within the building. Below this it was a very short distance to the natural soil. When the excavation was completed the site records were updated, and then we back filled the trenches and tidied up the site.

What you see is (not always) what you get? A final reflection on the analysis of the stone artefacts from Gledswood Shelter 1

Who would have thought a box of artefacts from a remote shelter in northwest Queensland could contain such a complex story of the past 10,000 years?  Well at least it has proved to be a much more complex story than I could have imagined and I have only managed to scratch the surface as part of my directed study. The project has proven to be more demanding in time and effort than any other subject I have undertaken and still there is so much that seems incomplete and in need of further research. There is more than a thesis waiting in just one square of excavation from Gledswood Shelter 1 (GS1).

Part of my study involved age-depth modelling. This is the process of using the radiocarbon dates obtained from the spits throughout the excavation to understand the history of sedimentation at the site. Age-depth modelling is a science in its own right and what I learned from my study was that GS1 warrants a thorough modelling of its history of sedimentation using some of the modern techniques available, such as linear regression, splines and interpolation. This work alone would be enough for a directed study project.

I also learned that what you think you see is probably not what you can see. My tendency was to see trends in the spits in terms of artefacts numbers and to believe that these trends were real. However, once these numbers were correlated with time in the age depth model a very different picture emerged. What appeared to be a peak in artefact numbers was not, and what did not appear to be a peak in artefact numbers was.


Evidence of the use of stone axes such as the axe pictured is seen as small basalt fragments throughout the excavation at GS1

Once the trends were understood it was time to make sense of this through researching the available literature. A trend towards increased activity at the site seems to correlate with a wider trend that occurred across northern Australia during the mid to late Holocene, where populations moved into more marginal areas exploiting food sources not previously used, such as the toxic seeds of cycads. These changes were believed to be responses to rapid climatic changes that required innovations in the way people lived off and used the land, and the technologies available to them. There are many more questions to be answered in relation to these responses to change. For example, there are reports that some sites show evidence of responses to change in the mid Holocene, whilst others show evidence later in the Holocene, sometimes a couple of thousands of years apart. The site specific nature of these responses is a complex question and GS1 still has many questions to be explored.

Perhaps this project taught me more about research than it did about GS1. Sometimes, when I thought I saw clear evidence of a pattern, there was a tendency to search for evidence that would support it. However, this had the effect of excluding information that might challenge my hypotheses. When I became aware of this behaviour I could adjust my approach to research and sure enough the result would often be quite different to what I believed I was observing.

This directed study has been a great journey and I have learned more from this topic than any other. Thanks to Lynley Wallis my Industry Partner who has assisted me throughout my project.

An analysis of the stone artefacts from Gledswood Shelter 1 – update 3

After sorting through, describing and categorising 936 artefacts I can definitely say that my skills in identifying and describing artefacts have improved. With more than 800 of the artefacts comprising flakes and broken flakes, each one had to be studied to identify the features that would enable me to determine how it had been made. Most of these flakes were made of quartz and, owing to the intrinsic properties of that raw material, determining the reduction process proved challenging at times.

After identifying the types, artefacts were then categorised by raw material type, counted and weighed.  The total numbers and weight of artefacts from each spit were volumetrically adjusted to account for differences in the amount of sediment removed from each spit. The results are shown in the graphs below. The graphs show total weight of artefacts in grams per kilogram and total count of artefacts per kilogram. Viewing both graphs shows clearly that, when a large artefact substantially affects the weight—such as in Spit 16 which includes a pestle—the artefact count is not affected and we are not misled by the results.

Artefact Numbers
Artefact Weight

The next phase of the project is to interpret the graphs and other recorded data, which will require consideration of several factors. Firstly, sediment deposition in the shelter is not consistent through time, so the spits do not represent equal periods of time. For example, Spits 20 to 16 represent almost 5000 years of time, meaning the bottom 20% of the excavation represents 50% of the time line. What appears in the graphs as a peaks in artefact counts and weights for the lowest two spits may actually be non-existent when the timeframe of deposition is considered relative to the other spits.

Even when volumetrically adjusted, artefact weights for each spit also need to be carefully considered, as it cannot be assumed that a high weight represents a greater level of activity in the shelter. For example, Spit 16 shows the greatest weight of artefacts for all spits; however, one of the artefacts it contains—a pestle—weighs more than 400g. In contrast, Spit 6 includes 130 flakes that only weigh 174g. The pestle may have only been used once, whilst the flakes may have been used multiple times. So in this case a lower weight could represent greater activity at the site on the basis of the artefact types found.

DSC_0011 A stone used for grinding found in Spit 16

Patterns that need to be explained also include changes in time through the raw materials present. In the lower spits (i.e Spits 20 to16) flakes are equally likely to be made of both quartz and quartzite. After this there is a gradual change, with an increase in quartz flakes and a reduction in the number of quartzite flakes. This change reaches a peak in Spit 6, with a ratio of 97:3 of quartz to quartzite flakes. Trying to determine what might have caused people to change their preferred raw material is one of the things I am exploring.

Selection of Quartz Flakes A selection of quartz flakes from Spit 6

Further afield there are different changes seen in the assemblages of other shelters in northwest Queensland that are not seen in Square B0 at GS1. For example, some shelters have shown changes in raw materials used at a specific time, and increases in the use and presence of grinding stones. These changes have not been seen in Square B0.

Once I’ve explored the patterns seen in  Square B0 I’ll then consider this in relation to the results from the excavation of the adjacent squares in GS1, other shelters on the Middle Park Station, and other shelters in the northwest Queensland region. This will help to understand whether the patterns observed are specific to the Square B0 assemblage, the GS1 shelter, the Middle Park Station area or whether they are part of a wider sequence of changes occurring in Queensland and beyond at the time.

An analysis of the stone artefacts from Gledswood Shelter 1 – Update

This is an update to my last posting for the analysis of artefacts from Gledswood shelter 1.

After receiving a large box of artefacts from excavation Square B0 in mid-April, I  set myself to the task of sorting through the material. This has involved working through each excavation unit (Spit) identifying the artefact types, including cores (complete or broken), hammer stones, grinding stones, and flakes (complete or broken).  For a broken flake I am identifying whether it is longitudinally or transversely broken and whether it is a distal, proximal, medial, and left or right fragment.

The artefact types are then categorised by raw material type. For example, quartz flakes are grouped together, transversely broken distal chert flakes are grouped together, and so on. The groupings from each spit are bagged and labelled in preparation for the next stage, which will include measuring, weighing and recording.

I am now about 45% of the way through this initial sorting phase before progressing to the measuring and recording stage. With each box of artefacts I open there is often something interesting and possibly unique to the spit. For example, Spit 16 contains a fragment of pestle which has been used for grinding materials which could have included ochre, clay, charcoal, seeds or other plant materials.

The spits towards the bottom of the excavation square (early Holocene in age) contain mostly quartzite artefacts. By around halfway up the sequence there is a sudden change and quartzite disappears from the assemblage and clear crystalline quartz becomes the dominant raw material. Further up the excavation this then changes to a mix of white, white grey and clear quartz. Why these changes have occurred will be considered as part of my final report.

OLYMPUS DIGITAL CAMERA A pebble used both as a hammerstone and also as a core for the removal of flakes

Throughout the Square B0 assemblage there is only a small percentage of chert and mudstone and thus far only two examples of chalcedony (both from the one spit).

OLYMPUS DIGITAL CAMERA A broken chalcedony flake with retouch

A small percentage of the flaked artefacts exhibit retouching along their margins. Towards the bottom of the sequence they are very rare and only seen on quartzite flakes. Towards the middle of the sequence retouching is also seen on chert, chalcedony and quartz flakes.

OLYMPUS DIGITAL CAMERA A broken chert flake with retouch

As more data become available through the detailed recording it will  become easier to determine when, and to what extent, these changes in material type have occurred through time. However, there are hundreds of artefacts and each one has to be analysed to determine how it was made. There is a high volume of quartz, which is the most difficult raw material for which determine the process of reduction. My only hope is that I can manage to stay sane through all of the analysis and recording.

An analysis of the stone artefacts from Gledswood Shelter 1

My directed study project is a part of a larger project that Lynley Wallis is conducting in conjunction with the Woolgar Valley Aboriginal Corporation at the Gledswood Shelter 1 in Northwest Queensland. A number of excavations were  carried out at this shelter in 2006 and 2008. The material from the excavation square, identified as square B0, is the basis for my research project. Excavation of square B0 went down to a depth of 100cm before being blocked by a slab of rock that had fallen from the roof of the shelter. Radiocarbon dating carried out at the site indicates that the material from this square starts at about 10,000 years ago at the deepest point and proceeds to the recent past. The excavation proceeded in twenty 5cm spits, with the material from each spit being sieved and bagged. The next stage of the project for this square is where I get involved.

The artefact material now needs to be cleaned, sorted into material types, weighed, measured and photographed and data needs to be recorded onto a spread sheet.

There needs to be a detailed analysis of the artefacts.  This includes a review of literature of lithic assemblages from the Holocene from other sites relevant to the study site. It also includes the production of a detailed report on the results of the study.

My directed study project is still in its early stages, with the current activity centred on the review of literature relevant to the area. I have just picked up my box of artefacts from the shelter, so now the exciting part starts. I have had a quick look through some of the artefacts from several of the spits and can already notice some significant changes with obvious differences in the presence of some artefacts.

My next update will be during the initial phase of sorting and categorising and I will provide some details on what I am finding.