New processes at Zagora in 2013: flotation of marine debris and seeds

Roza pouring a bag of soil from one of the excavation areas into the first phase of wet sieving
Maria-Roza Beshara pours a bag of sample soil debris from one of the excavated occupation levels into the flotation tank. © PHM; photo by Irma Havlicek
by Irma Havlicek
Powerhouse Museum Web Producer

For the first time at Zagora in 2013, soil samples were collected and processed through flotation in order to recover organic remains to find the charred, small, light material which floats to the surface of the water. This process had not been developed 40 years ago when the excavations of the 1960s and 70s took place at Zagora.

Organic plant material such as wood and plants decomposes over time, so such material from the period of the Zagora settlement no longer exists. If it has been burnt and transformed into charcoal, it can survive thousands of years which makes it extremely valuable in providing information about the kinds of plants which occurred at particular locations at different times.

The existence or absence of organic material such as tiny fish bones, shell fragments, seeds and charcoal in occupation deposits can provide evidence of ancient diet and domestic and industrial economy and activities at Zagora. We can also learn about the general environmental conditions in which the Zagoreans lived because organic material can inform us about plants that aren’t exploitable by humans but still throw light on the climatic and other environmental conditions there at that time. Fragments of heavier material such as obsidian, slag and pottery sherds can also be found through this process. If sampling for organic remains had not been undertaken, this information would be permanently lost.

Evidence of what they were cultivating, processing and consuming will provide valuable insights into the agricultural patterns, health and lifestyle of those living at Zagora three thousand years ago. The relative densities of the material across the site will also provide evidence about how different households and areas of the site of Zagora were organised and functioned.

Meg, Stavros and Lesley examining the recently installed flotation water drum.
ZAP Directors (from left), Meg Miller, Stavros Paspalas and Lesley Beaumont examine the flotation water drum. © PHM; photo by Irma Havlicek.
For example, does the distribution of organic material help us to distinguish domestic, social and industrial areas across the site? Were there focal points for social interaction? What is the relationship between what organic materials are found and the kind of built structures in or near which they were found? How might this help us to better understand what took place in and around the buildings?

Charcoal can provide a lot of information about the surrounding vegetation, the trees and other plants which were used for building and fuel at Zagora. Under the right preservation conditions, charcoal can even indicate the type of wood that was burned and whether it was slow- or quick-burning wood which provides evidence of what kind of purpose it would have served best – for example, slow-burning wood for food preparation, and fast-burning for industrial purposes, eg, metal work.

Rock crystal appears to be among the sample residues. It will be interesting to find out if the rock crystal is local to Andros or not. If not, it will have been imported, and the type of rock crystal may indicate where it was imported from, which would be an indication of a trade route. If the rock crystal is detritus then that would suggest the rock crystal was worked on site (for example to make jewellery or seals) which is an indication of industrial activity.

Evidence from organic remains can also help us to challenge any assumptions we may have. For example we can’t assume that because they were living next to the sea they were fishing and fish was part of their diet.

Before describing the flotation process, a little background will help to set the scene. The Zagora Archaeology Project (ZAP) Project Directors – Professor Meg Miller, Associate Professor Lesley Beaumont and Dr Stavros Paspalas – wanted in 2013 to expand the kinds of data sought from the project. They had contacted Dr Evi Margaritis, an archaeobotanist (archaeological plant specialist, with expertise in the analysis of plant remains) to determine how best to achieve flotation analysis for the Zagora project and how this could be practically possible in the field. Sampling strategies and the goals of the study were set between the directors of the excavation and Evi.

Beatrice McLoughlin and Dr Evi Margaritis
I wasn’t at Zagora on the day Evi was there, so I only managed to photograph her relaxing with other team members after a hard day’s work. Evi is in the centre; Beatrice McLoughlin is at left. © PHM; photo by Irma Havlicek
Evi was then an Assistant Professor at the Cyprus Institute. Shortly before the 2013 Zagora season, she was appointed as a Post-Doctoral Marie Curie Fellow at the McDonald Institute for Archaeological Research at Cambridge University. However before moving to England, Evi was able to spend some days at Batsi/Zagora during the season to organise and oversee the purchase, construction and set up of the gear required for the flotation.

I’ve come to realise that there are many undocumented challenges in an archaeological project. When the research is written up, we will learn what evidence was found from the flotation process, and what it indicates about life at Zagora.

What won’t be evident is that, after a hard day’s work on site, team members had to drive around the island to source and purchase a 44-gallon metal drum, tap, and all the other items needed for the flotation system. It then had to be constructed and tested at Batsi, and then loaded into a vehicle for transport to Stavropeda – from where team members had to carry all the flotation equipment down the sometimes steep and rocky path to Zagora.

Steve Vasilakis on the Zagora escarpment
Steve Vasilakis on the Zagora escarpment. I didn’t manage to get a shot of him getting the flotation system operational. There’s always a lot going on at Zagora so it’s not possible to capture everything photographically. Photo and © Kristen Mann.
After getting the gear to the site, the team, led by Steve Vasilakis, was keen to get the system up and working as quickly and efficiently as possible – not an easy task as the water source was several hundred metres away up the hill.

That meant getting a 450-metre long hose attached from the water source to the water drum. I don’t know about you – but I have enough trouble with a 12-metre long hose trying to avoid knots and kinks on those rare occasions I water plants in our garden. So the thought of how to successfully wrangle an almost half a kilometre long hose makes my head hurt.

I remember over a period of days, watching Steve’s efforts in hot and humid conditions to achieve free-flowing water at good pressure to the drum. It required many, many trips up the hill to the water source and back down the hill to the water drum, with a great deal of trial and error, moving the hose and water drum positions to gain the optimum result. Any slight kink in the hose compromised the water pressure. For a conscientious person like Steve, he was also suffering because the time it took to achieve running water for the flotation process was time he was not able to give to the excavation area team of which he was a member. I know if he could have split himself into two so he could work in both places at the same time, he would have done so. Steve’s stamina, tactics, hard physical work and perseverence paid off, and he got the flotation system up and running.

Evi had selected a student whom she had trained in other projects in flotation, Maria-Roza Beshara, to conduct the process at Zagora. Roza (as Maria-Roza asked to be called), a student in the Archaeology and History of Art Department of the National and Kapodistrian University of Athens, who was due to complete her degree in a few months, kindly demonstrated and explained the process to me.

Roza on the track to Zagora.
Roza on the track to Zagora. © PHM; photo by Irma Havlicek

Once excavation of the trenches had reached significant levels (ie, below topsoil and backfilling), samples of soil and other debris were placed into heavy duty plastic bags, labelled with the date and precise location of the sample (both lateral and depth), and carried down to Roza. The average volume of each sample was 12-15 litres.

She placed the material from each bag into the flotation drum the team had constructed. The drum contained water with wire mesh attached across it a few centimetres below the surface of the water.

Roza pouring a bag of soil from one of the excavation areas into the first phase of wet sieving
Roza pouring a bag of soil from one of the excavation areas into the first phase of wet sieving. © PHM; photo by Irma Havlicek

Roza washed the samples by hand in the water, gently loosening the earth away from the other material, and allowing the earth to sink down through the wire mesh into the lower section of the drum. You may like to see the post I published last year about a related process, dry sieving.

Roza washing the material in the water to remove soil from the stones, seeds, bones and other material
Roza washing the material in the water to remove soil from the stones, seeds, bones and other material. You can see a round metal sieve to the left of the drum, into which the lighter floating material flows. © PHM; photo by Irma Havlicek
A closer look at the washing of the debris
A closer look at the washing of the debris. © PHM; photo by Irma Havlicek

What remains on top of the wire mesh inside the drum is the washed heavier material – stones, sherds, rock crystal, etc. The lighter material – organic plant material, seeds, charcoal, etc., floats to the top of the water, and is swished off by Roza into the round tin at the side of the drum (see closer shot, below).

The lighter material which had floated to the top of the water, including seeds, small fish bones and other material which can provide evidence about the lifestyle at Zagora.
The lighter material which had floated to the top of the water, including seeds, small fish bones and other material which can provide evidence about the lifestyle at Zagora. © PHM; photo by Irma Havlicek

Roza separately collected the lighter and the heavier material, and took it to the courtyard area of the dig hut to be placed on top of square sheets of material so that it could be dried. Each sample is always labelled to identify its source, the date on which it was collected and the volume of the original sample.

Roza places the washed debris on sheets on the ground to dry, in preparation for sorting
Roza places the washed debris on sheets on the ground to dry, in preparation for sorting. Tessa Morgan looks on at right. © PHM; photo by Irma Havlicek
Roza spreads out the debris to enable efficient drying by air
Roza spreads out the debris to enable efficient drying by air. © PHM; photo by Irma Havlicek
Soil samples drying in the courtyard of the Zagora dig hut.
Soil samples drying in the courtyard of the Zagora dig hut. © PHM; photo by Irma Havlicek
Soil debris samples drying in the dig hut
Dried soil debris inside the dig hut, awaiting sorting. Note that there is an identification tag for each sample. © PHM; photo by Irma Havlicek

The photos above and below clearly show the difference between the heavier material (above) which was captured in the water tank in the wet sieving part of the process and the lighter material (below) which was scooped off the surface of the water in the flotation part of the process. Roza painstakingly goes through all this debris to look for material which will be taken to the Archaeological Museum at Chora for further analysis.

Roza about to tip the wet 'flotation' material onto paper towel for drying.
Roza about to tip the wet ‘flotation’ material onto paper towel for drying. © PHM; photo by Irma Havlicek
The tipped 'flotation' material on paper towel to dry in the Zagora dig hut courtyard.
The tipped ‘flotation’ material on paper towel to dry in the Zagora dig hut courtyard. © PHM; photo by Irma Havlicek
A close up of the wet 'flotation' material being placed onto paper towel for drying.
A close up of the wet ‘flotation’ material being placed onto paper towel for drying. © PHM; photo by Irma Havlicek
The 'flotation' material wrapped up in paper towel to dry.
The ‘flotation’ material wrapped up in paper towel to dry. © PHM; photo by Irma Havlicek
The 'flotation' material wrapped up in paper towel to dry
The ‘flotation’ material wrapped up in paper towel with its identification label visible. © PHM; photo by Irma Havlicek
'Flotation' samples, wrapped in paper towel and hung up to dry
‘Flotation’ samples, wrapped in paper towel and hung up to dry in the dig hut. © PHM; photo by Irma Havlicek
A longer view of Roza doing her sorting in the Zagora dig hut.
Roza doing her sorting in the Zagora dig hut. It’s probably nearing the end of the day because through the doorway we can see Rudy Alagich returning with tools from the day’s excavation. Rosa moved her work table around to get the best available light as it changed during the day. © PHM; photo by Irma Havlicek
Roza sorting the soil debris in the Zagora dig hut with her paintbrush and tweezers.
Roza sorting the soil debris in the Zagora dig hut. © PHM; photo by Irma Havlicek
Roza sorting through a tray of debris from one of the excavation areas using a paintbrush and tweezers.
Roza using a paintbrush and tweezers to sort through a tray of debris from one of the excavation areas. © PHM; photo by Irma Havlicek

The sorting has to be methodical to be sure not to miss anything of significance. Roza first spreads the material across the tray in a fine layer leaving a little space along the bottom closest to her. She then begins finely brushing the debris gently towards herself, keenly examining every item as she goes.

A close up shot of Roza sorting through the soil debris. Observing her keen focus and methodical and meticulous work, I understood why Evi had entrusted this work to Roza.
A close up shot of Roza working with her paintbrush and tweezers. I was amazed to see how Roza was able to discern specks of fishbone or charcoal as small as a pinhead. If there is a small number of a category in a sample, Roza counts how many there are. If there is a large number, she makes an estimate, for example, 100-130, and marks that on the label. © PHM; photo by Irma Havlicek

When Roza finds material of significance she picks it up with tweezers and places it in a pile of material of that category on the table (see the two images, below).

Roza sorting through one of the trays of debris using a paintbrush and tweezers.
You can see in front of her the small piles of significant material Roza has sorted out of the tray of soil debris. Seeds and charcoal can look alike and Evi’s expertise is required to make a definitive identification. © PHM; photo by Irma Havlicek
Some of the piles of sorted material, clockwise from left: pottery sherds, seeds, fish bones, rock crystal and charcoal.
Some of the piles of sorted significant material, clockwise from left: pottery sherds, animal bones, fish bones, rock crystal and charcoal. © PHM; photo by Irma Havlicek

Here is a more complete list of the categories of material Roza collected: seeds, charcoal, pottery, rock crystal, fish bones, obsidian, flint, beads, shell, animal bones, microfauna.

Once these were sorted and counted or estimated, and the bags labelled, they were delivered to the Archaeological Museum at Chora where Evi Margaritis will conduct research on the finds. Evi is responsible for detailed analysis on the seeds but some of the material, such as charcoal and rock crystal, may also be examined by others. Evi will synthesise the findings and write a report for the Zagora project directors about the results of the flotation findings from the Zagora 2013 field season. 

The flotation/wet sieving drum with the Aegean Sea visible beyond.
Hero shot of our flotation/wet sieving drum with the Aegean Sea visible beyond. © PHM; photo by Irma Havlicek

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