As part of my directed study I was required to do some research into hearth detection projects that had been conducted in similar environments and/or with similar geophysical equipments. Upon researching this area it became evident that only a small percentage of archaeological work has been conducted with geophysical instruments in the past. This is possibly because of the perceived high cost of geophysical instruments, a lack of training available at university level and as a result of a lack of competent technicians with the ability and experience to detect subtle targets. By subtle targets I mean targets/anomalies that that may not be apparent straight away in data sets and that may require processing to extrude them from the rest of the unwanted data set. Ian Moffat and Lynley Wallis did a very similar geophysical study in inland North Queeensland using magnetic methods, whereby they attempted to locate hearths and middens in areas where they were known to be. Unfortunately their study was unsuccessful, as hearths were not easily located, although the study provided me with very useful information regarding which choice of magnetic instrument to use and the line spacings between survey lines and survey sizes. There have been plenty of successful studies of this type conducted throughout the U.S. using both magnetic geophysical instruments and ground penetrating radar, but I noticed very few successful studies in Australia. So I decided to employ both types of geophysical instrument for this study to increase my chances for success (both geophysical instruments pictured below). I found plenty of case studies done by Larry Conyers to find hearths of Native American peoples using ground penetrating radar. His methods of data interpretation and processing gave me a good idea of what to look for, the GPR profiles to be collected and the data processing that may be required to extrude these features if the profiles are full of noise.
Figure 3 Figure 4
Figure 3 (above left) – GSSI SIR 3000 radar system, a 400 MHz antenna is mounted under the centre of the survey cart. Distance travelled is measured with an encoder wheel attached to the rear wheel. Figure 4 (above right) – A Bartington Grad601 single sensor fluxgate gradiometer.
The background research phase of this study provided me with some helpful information about survey methodology that may be suited specifically to this type of survey. I decided that, rather than have large survey areas, I would have small 10 x10 m plots which would result in smaller more manageable data sets. Data was collected over each 10m x 10m grid with both ground penetrating radar and gradiometer. Line spacings were set at 1m, which admittedly could be a mistake, and which proved to be the case in Wallis and Moffat’s study. I’m hoping that a gradiometer, being a more sensitive instrument to local changes in the earth’s magnetic field, will have the ability to detect hearths at 1m spacing as opposed to something like a proton precession magnetometer (used in Moffat’s and Wallis study) which was not capable of doing this. Something I have learnt regarding my magnetic survey methodology is that, rather than tightening grid spacings, it can be just as effective—if not more so—to survey a grid in one orientation, for example east–west and then in an opposite orientation, for example north-south. This methodology has the potential to detect magnetic fields on one axis of the gridded area that may not be strong or apparent on the other. I anticipate that GPR will not be so greatly affected by line spacing due to the 400 MHz antenna’s footprint (the antenna focusing range) and the ability of the signal to effectively propagate through the soil type at this particular site. I predict that GPR will be more effective at this site than many would expect, as test scans easily detected targets from 0-2m deep. Hopefully the discussion about my results in the next blog backs this statement up!!
I have started my Graduate Diploma in Archaeology this year and as part of my study I am completing a Directed Study in Archaeology. I am very excited about this project, as I am able to research a project that has been of interest to me since I discovered a wonderful set of artefacts in Oatlands, Tasmania, in January 2012.
The artefacts are toys that were discovered under the floor boards in a Gaoler’s Residence in the Oatlands Gaol, Tasmania. There are many different toys, including handcrafted wooden animals, dolls’ clothing, doll’s house pieces, marbles and a wooden whistle.
I am working at the moment on finding out what each toy is and hopefully their ages. I then hope to connect the toys to the children who lived in the residence, starting from the Gaol’s construction in 1836 all the way to 1930.
After the research is complete I hope to travel back to Tasmania and conduct a community project at the Oatlands Gaol museum for the people of Oatlands. I want to bring the toys to the community and communicate with them the significance of the artefacts and how they connect to the history of Oatlands and the people who once lived there.
Camel – maybe from a Noah’s Ark toy set
One of the rooms where some of the artefacts were found under the floor boards.
The Oatlands Gaol where the artefacts were found
Figure One: Group photo in Port MacDonnell, SA. Photo taken by Nita von Stanke. 16/02/13.
By Daniel Petraccaro, Masters in Maritime Archaeology Student Flinders University.
Nothing can compare to the field school experience offered this year to the graduates enrolled in the Flinders University Maritime Archaeology Programme. The Maritime Archaeology field school was based at Port MacDonnell, in South Australia’s Southeast region, and was held from the 3rd to 16th of February. The rigorous two-week program offered students an introduction to techniques from underwater surveying, mapping, and photography to recording (figure 2).
Figure Two: Students Daniel Petraccaro and Hunter Brendel with Supervisor Gay Lascina start mapping the ketch Hawthorn. Photo by Chelsa Pasch. 06.02.13.
Posted in Posts from the field, Student Posts
Tagged Archaeology, australian built ship, carpenter rocks, centreboard, couta boat, daniel petraccaro, diving, Field School, Flinders University, hawthorn, Huon River, keelson, ketch, Maritime Archaeology, Port MacDonnell, Port MacDonnell South Australia, shipwreck, total station
A lone dumpy stands on site.
On the Monday of February 4th, a small group of novice archaeologists packed into a small bus and proceeded to the old lighthouse of Port MacDonnell to begin, for most, our first taste of field archaeology. The 11 archaeologists were divided into two groups of four, and a group of three. Of these, two groups were to commence a baseline/offset survey, and the other group was tasked with conducting a dumpy survey of the sight. I was a part of that dumpy team.
None of us knew what this consisted of.
The dumpy team quickly learnt the difficulty of conducting a dumpy survey on the edge of a cliff, along with a developing hatred of dense vegetation. Oh, and the local fly’s which bit and stung while resisting copious amounts of AeroGuard. The wind constantly barraged the 3 metre ranging pole, making readings difficult to get exact; but no amount of foul play from nature would stop us from producing that map. One particular issue, however, did not come from nature but the irritating lack of straight lines when recording the walls. Baffling us, it became clear after double checking our measurements that perhaps they just weren’t made straight and parallel.
In all, for our first field experience we could not have predicted a tougher way to learn; but this made us strong. At the end of the day, the dumpy team was working in perfect unison to create a rather nice, if a bit unfinished, map showing a cliff, dense vegetation and a series of small walls.
Eleven archaeology students left campus early on a Sunday morning, bound for the Hist. Arch. Field School at Port MacDonnell. Seven very long hours later, we arrived and settled in for our first night. Surprisingly, the whole class was ready and waiting to begin long before the agreed meeting time the next morning! Our first task was to survey and record the extensive glass and ceramic scatters across the cliff at the site of the old lighthouse.
Our group spent one and a half blissful days at Transect A (for ‘Awesome’) enjoying a spectacular view on the west side of the cliff. We set about recording each artefact in our sample, a task we embraced as we employed an ingenious labelling system that allowed us to give each artefact a numerical title, followed by a letter of the alphabet to separate it from the other countless sherds of non-diagnostic glass in the quadrat. Transect Awesome well and truly lived up to its name and we left it with fond memories (and many photos).
The spectacular view from Transect A.
Recording artefacts along Transect A.
We then set up Transect B (rather hopefully named ‘Brilliant’) and once again employed our ingenious labelling system. However, almost two hours later we had barely progressed a third of the way through our first quadrat. The problem was quickly identified – our fantastic labelling system, which worked so well at Transect Awesome, had failed us on the north side of the cliff where the artefact scatters were far denser. We learnt a very valuable lesson at Port MacDonnell, always re-evaluate your labelling system when you move to a different part of the site – unless, of course, you want to spend numerous hours working at a snail’s pace and thoroughly confusing yourself in the process!