Tag Archives: Midden analysis

Midden sample floatation process going swimmingly

By Adrian Fenech, Graduate Diploma in Archaeology Student

I have started the floatation procedure that I described in my earlier post and it is proceeding reasonably quickly. I am still thinking about the defloccation procedure but I am unsure if I will have enough time to accommodate it.

Despite the mess of sugar water I am making in the archaeology labs, the floatation is going well because it has managed to float quite a few materials that will be picked out in the sorting stage. So far, the dominant floated materials have been charcoal and vegetation, the former would have been difficult to locate in sorting. This is because of the many other dark-coloured materials in the samples. The photos below show the resulting fractions produced by the floatation work.

Light fraction: material which floated

Heavy fraction: material that sank

The photos show the contrast in materials that the floatation produced. The light fraction consists primarily of charcoal with some vegetation and a few shells. The heavy fraction is dominated by shell with a considerable amount of stones and some faunal material (from a glance). I’ve only just begun the slow process of sorting through the heavy fractions; hopefully I’ll find some non-molluscan fauna!

I am considering the defloccation procedure because the sugar water is often black after its second floatation. After the materials have been rinsed off, they are still encrusted with a considerable amount of sediment. A test will have to be performed; two samples of materials, one with defloccation performed and one without will be sorted and the ease of sorting will be compared. This will be subjective, though because it will be difficult to get two samples that are equal in quantities of material types.

Sugar is useful in archaeology

By Adrian Fenech, Graduate Diploma in Archaeology Student

The directed study I am working on involves reanalysing material excavated by Mick Morrison from Weipa in northern Queensland and uses sugar to aid the ‘floatation’ lab technique. I’m doing this because previous research projects on shell mound sites in northern Australia suggests that they contain very few faunal materials other than shellfish remains. The aim of this work is to find if the low recovery rate of faunal materials in samples is due to taphonomic or sampling technique biases. I am going to use chemical floatation to assist the sorting and faunal identification processes.

The chemical floatation process involves dry sieving the archaeological material and then immersing it in water that has been treated with some kind of chemical (Ross and Duffy 2000, p 33). This is designed to change the specific gravity of the water to separate materials that have different weights. For reasons of personal safety and economy, sugar will be used, hopefully the lab technicians, John and Chantal will not think that I am cooking in the lab.

A secondary process I am considering is defloccation which involves swirling archaeological materials around in a solution of water and some form of cleaning agent. I will be playing this by ear until I can see if the floatation cleans the material in any way.

Dry sieving

References

Ross, A. and R. Duffy 2000, Fine mesh screening of midden material and the recovery of fish bone: the development of floatation and deflocculation techniques for an efficient and effective procedure. Geoarchaeology 15(1): pp. 21-41.

Vale, D. and R.H. Gargett 2002 Size matters: 3mm sieves do not increase richness in a fishbone assemblage from Arrawarr 1, an Aboriginal Australian shell midden on the mid-north coast of New South Wales, Australia. Journal of Archeological Science. vol. 29: pp. 57-63.