I excavated 5L of sediment – what now?

Excavations at Gruta da Companheira finished last week, but that doesn’t mean the work stops. Due to its location, all the excavated sediment from within the cave is placed in bags and taken to the laboratory to be processed. It is up to us, here at the ICArEHB laboratory, to sieve, sort and organize all the archaeological materials. Want to know more? Then pull up your sleeves and let’s get ready to work – I hope you brought your waterproof boots.

Washing the sediment and materials

Because the sediment is muddy and very dark, we wash the sediment before we sort it. We weigh the sediments and the limestone rocks, which are then washed in sieves with fine meshes. These meshes allow us to clean the sediment without losing small archaeological materials – goodbye fine dirt, hello little rabbit bones. After this, the sediment is left to dry.

The materials which are recovered at the site and have individual three-dimensional coordinates are placed in bags with their ID labels and are taken to the lab. Once in the lab, we wash the materials, make new laboratory labels and organize them for later studies.

Sorting the materials

After the sediment is dry, we begin to sort! Although sediments are very important, and can tell us a lot about site formation processes, for some areas of the site we don’t keep it or study it. Which means from all that sediment, we need to retrieve archaeological materials which will then be placed in individual bags with Bucket labels. These materials are small chips of rock – like quartz, chert or quartzite; bones, which can be as small as 1mm; charcoals; and other materials.

Sorting these materials is important because they are essential to understand the human groups that inhabited the Companheira cave. Processing the sediments and archaeological materials in the lab or in the field is a key task, which allows us to retrieve detailed information which may have been “invisible” while we excavate.

Our PhD students are sorting the Gruta da Companheira buckets – separating materials like bones or lithics. After being sorted, these materials will be organized and labeled and are ready to be studied by a specialist.

The takeaway message

Laboratory work is essential for archaeology. The excavation methodologies used in the field are essential for good results. But laboratory methodologies are also key– these methodologies may be different and adapted to the chronologies we are excavating, the type of site or sediment, or even the type of data we want to retrieve.

Plus, it’s a fun task. Who doesn’t want to hose sediments with fresh water on a hot summer afternoon. Washing, sorting and organizing needs a lot of collaboration between the team, and you can always count on a fun time while still doing science.

This said, our laboratory team for the Gruta da Companheira excavation was awesome! We’d like to thank Daniela Maio, Joana Belmiro, Jovan Galfi and Roxane Matias for the hard work and fun times! May more washing and sorting days follow!


Author: Joana Belmiro and Roxane Matias

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