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Where Did You Come From and Where Did You Go?

At the Barnham excavation, there are two areas where digging has actively taken place in recent years; Area IV/VI, a cobbled palaeo-lakeshore, and Area III, roughly in the middle of the former lake. We know that the latter area used to be a lake, because of the fine sediments characteristic of fluvial deposits, but also because of the high number of fish bones, as described by Tess Bakker in a previous blog. From these fish species, we can determine whether the water was fresh or perhaps brackish, whether it was flowing or still standing and many more aspects. However, there are also features to the waterbody we can only study by looking at the objects that do not naturally belong in the water, but somehow ended up at the bottom of the lake. One of these features is the direction of the lake’s current. By measuring the direction in which elongated objects are oriented, we can reconstruct the axis and direction of the current. But how do we measure orientation and thereafter determine the direction of the current?

Excavations in Area III

First of all, elongated objects can be bones and artefacts, but also unworked flint, of which the longest axis, referred to as ‘a-axis’, is 1.5 times larger than the ‘b-axis’, which is perpendicular to the ‘a-axis’. Holding a compass with a rectangular outline parallel to the object’s most inclined axis, we can read the object’s orientation relative to the magnetic north off the compass’ dial.

Secondly, the orientation data will be plotted in a so-called ‘Rose-diagram’ after all measurements have been digitalized. The plotted data should show a concentration in a general direction (e.g. ‘north by northeast’ or ‘southwest’), which will be the direction from which the water was flowing. The measurements point to the source of the flowing water, since the highest end of objects will be forced to point downstream by the moving water, resulting in the object to dip in the direction of the water’s source. However, several processes can influence the precision of our measurements. These can be large animals drinking from the lake and by accident walking on the deposited objects, affecting their orientation and dip, a process called ‘trampling’, but it is also possible that some of the objects we find were not transported by water, but entered the lake’s sediments because an animal died in shallow areas of the lake, or early hominins discarding bones of butchered animals and/ or threw rocks in a lake for reasons we can only speculate about.

To differentiate objects deposited by flowing water from intrusions, we measure the dip of the objects with a clinometer. If items are positioned vertically, they are more likely to be unaffected by the current and hence not very informative for our main research question. This way we can make a general distinction and make our results more precise and reliable.

Although we presume that the objects in the lake did not leave behind broken marriages during their travels, but in order to learn more about our palaeo-lake we still ask them the same question Cotton Eye Joe was asked: “Where did you come from and where did you go?”

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Suds Versus Sods

Written by Simon O’Connor, a volunteer at the Barnham excavations.

In the wet sieving area at Barnham you will see rows and rows of buckets with thick chocolaty mud in them. This is the vital disaggregation stage that is needed to allow the sediments to wash away leaving stones, teeth and bones behind in the sieves. To achieve disaggregation there is a magic ingredient that we add to the sediment and water mix. The secret ingredient is a 1/3 of a cup of biological detergent powder.

Stirring sticky sediments

To understand what is happening here we needed to delve into a little soil science. The sediments in our case are a mixture of sands, silts and clays. Sand and silt grains will not stick together, but clay acts like cement gluing everything together. The property of clay particles that causes this is a negative charge to each particle. If we added clay particles to distilled water they would disperse easily as the like charges of the particles repel each other in the same way as like poles of a pair of magnets do. However ground water in this area contains positively charged ions of calcium and magnesium that attract the clay particles causing them to clump together in a process called flocculation. Flocculated clay particles are the glue that cements the sand and silt together.

Detergent powder contains a water softening ingredient called sodium polyphosphate. When this ingredient is added to water the polyphosphate disassociates from the sodium. The polyphosphate has lots of negative charges and wraps itself round calcium and magnesium ions neutralising their charge in a process known as sequestration. The sodium ions replace the calcium and magnesium ions. They differ from calcium and magnesium ions in that they have a single positive charge rather than a double charge of the hard water ions. They also attract an insulating layer of water molecules (know as a hydration shell). For these reasons sodium ions are much less effective at flocculating clay particles. So a bit of a stir in water is sufficient to disaggregate our sediments when we add the magic 1/3 of a cup of detergent powder. 

This proves that a few suds are more than a match for the rock hard sun baked sods at Barnham!

Smooth sieving
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How to Get a Workout While Wet-Sieving

Written by Carli Peters, a student volunteer at the Barnham excavations.

Excavated sediments drying after being brought up in bags

During the first week of this years excavation I discovered the best way to get in shape while working on an archaeological site: wet sieving. This may sound strange at first, since wet sieving itself is not that physically demanding. However, it is not the wet sieving itself that is a great workout, it are all the processes associated with wet sieving that are physically intense.. and that is where I come in.

At Barnham all the sediments that are going to be sieved are dried first after which they are soaked with washing powder (see tomorrow’ s blog by Simon O’Connor). This means that the sediments need to be moved around after they are excavated. I am in charge of all of these processes and thus mostly spend my days walking around with sediments bags and buckets filled with sediment. During the first week of the excavation I transported 2166 litres of sediment, which is the equivalent of 3465.6 kg (twice) and I walked approximately 15 km a day while doing so.

Buckets of soaking samples waiting to be sieved

So if you ever feel like you could use a good workout for the day, you are welcome to give me a hand -it will take some of the weight of my shoulders!

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Small Finds, Big Pictures

Written by Tess Baker, a student at the Barnham excavations.

Since 2013, an international group of researchers and archaeology students are searching for traces that extinct human species may have left at the archaeological site Barnham East Farm. Earlier research showed that early humans lived in the region around the site at approximately 420,000 years ago, in a warmer period between two glacial periods.

Mandible of a Vole with incisor and molar

When archaeology is mentioned in the media, often spectacular finds, such as fossils of Pleistocene megafauna, and tools used by humans are covered. At the excavation at Barnham East Farm, a large number of remains from small animals has been found. Although these finds may be seen as less spectacular on first sight, they can indicate valuable information on archaeological sites.

The remains of small animals can, among others, be used for climatic and environmental reconstructions and dating of the site. For example, over time the enamel thickness and the height of the crown of water vole molars has changed, and because certain characteristics only occurred in a specific time frame, water vole molars can indicate the age of a site. 

Molars of a Vole

Bones from the European pond terrapin are also found at Barnham. The European pond terrapin needs a relative warm summer temperature for the eggs to hatch. Therefore, the European pond terrapin remains found at Branham East Farm indicates that the summer temperature 420,000 years ago was warmer than the current summer temperature. Remains from several species of fish has also been found during the excavation from, i.e. tench and pike. Fish generally live in a specific environment and fish remains found at archaeological sites can therefore indicate, among others, salinity, seasonality, type of water body, such as open water or floodplain. 

The valuable information small animal remains can tell us about the environment, climate and dating of the site, shows that the remains of small animals are for archaeologist just as important as elephants and large cats. This is also why all the sediment from the pit with a good preservation for animal bones is sieved, as without the sieving station, a large percentage of the small animal remains would be lost.  

Vertebrates of Pike
Teeth of Tench