Yes, I agree with you that one cannot generalise about recovering techniques. Totally agree with Eleni that extra dry environments can render organic material very brittle. From my own experience, for what it is worth, every sample needs to be assessed separately, whether ones needs to float or dry sieve. I have noted that in Greece where chaff exists, water flotation could destroy the evidence, in that it breaks in such small particles that it goes through the mesh and gets washed away. However, in no way though, should we reduce flotation!
From: The archaeobotany mailing list <[log in to unmask]> On Behalf Of amaia arranz
Sent: Saturday, March 24, 2018 9:55 PM
To: [log in to unmask]
Subject: Re: tuber exploitation and flotation
To avoid any misunderstanding I should state that at no point I've argued against the use of flotation (nothing further from the truth! I use flotation always in my sites!).
I simply noted that it may not be the best technique to recover certain types of plant macroremains (e.g. underground storage organs). And this issue is nothing new, it has previously been highlighted by other authors (e.g. Hather, Hillman etc).
In relation to the environments in which this phenomenon has been attested, as you say it does happen in hyper-arid environments and Shubayqa is a good example of it (see also Hillman 1989).
However, this phenomenon has also been noted by archaeobotanists working in arid (average annual rainfall 100-300 mm) and semi-arid environments (i.e. average annual rainfall 300-400 mm) such as southern Syria (Tell Qarassa), northern Syria (El Kowm), Iran (Ali Kosh ) and Jordan (Kharaysin) to mention a few.
I’d also like to add that the process of plant disintegration is a complex one. In the case of the charred tubers I analysed, they desintegrated completely or almost completely when they entered in contact in water. The wood charcoal remains survived comparatively much better, and most of them floated to the surface normally. However, there were some pieces that desintegrated or simply sunk (I’m currently analysing these latter wood charcoal pieces for comparison).
Unfortunately, these differences cannot be accounted for factors such as the type of environment or soil characteristics alone (i.e. the fact that a site is located in X area does not neccesarily mean that plant desintegration will occur). There are more issues that should be considered.
But I agree Eleni, it is important to evaluate each case individually.
Best wishes,
Amaia
On 24 Mar 2018, at 18:04, Asouti, Eleni <[log in to unmask]> wrote:
This is a very interesting video Amaia. What it shows so vividly applies only in certain types of sedimentary environments (SBK is a prime example); their common denominator is hyper-aridity. D Pearsall has already described this phenomenon and the conditions under which it may have a significant negative impact in her Paleoethnobotany volume (2nd edition, 2000, pp.82-84):
“dry sieving [should be used] instead of water flotation in soils that are habitually dry … Charcoal that is rarely wetted in the soil may “explode” on contact with water.” (and the she goes on to describe a range of methods and sieving apparatus that can help addressing such situations)
Were it the case that this is a “problem that researchers working in southwest Asia OFTEN face“ (my emphasis), then all of us would have had very little to go about re: adequately retrieved primary data sources. Any arguments against using flotation need to be fully qualified and tested on a site-by-site basis. I am sure that all archbots would agree that we really don’t need uncooperative field directors hiding behind excuses such as “flotation destroys everything therefore it is not necessary”.
All the best,
Eleni
___________________________________________
Dr. Eleni Asouti
Reader in Environmental Archaeology
Director of Postgraduate Research
Department of Archaeology, Classics and Egyptology,
University of Liverpool
12-14 Abercromby Square
Liverpool L69 7WZ, UK
Tel: (+44) 151 79 45284
From: The archaeobotany mailing list <[log in to unmask]> On Behalf Of amaia arranz
Sent: 24 March 2018 13:18
To: [log in to unmask]
Subject: tuber exploitation and flotation
Dear all,
For those that are interested in prehistoric underground storage organs (USO) here is a link to a recently published paper from a late Epipaleolithic site in Jordan (free download for 50 days):
I’m grateful to all the listmembers that contributed to this study in one way or the other.
In particular I'd like to draw your attention to the supplementary video S1. This video was recorded to visualise a problem that researchers working in southwest Asia often face: the desintegration of plant remains during flotation. The video shows how wood charcoal and underground storage organs completely desintegrate when they enter in contact with water. We would like to encourage people to pay attention to the flotation process, and in so doing limit the biases associated to sample processing.
Hope the results are useful for some of you,
With best wishes,
Amaia