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Publicado el 28 de November de 2013 por Marina Lozano

Digging in Atapuerca

I started digging in Atapuerca in July 1996. Since then, the methodology used to excavate has been changing, adapting to technological advances, although the recovery and the extraction of parts is still done manually and thoroughly. Every year, between June and July, an excavation campaign in the site of the Sierra de Atapuerca takes place for a month or a month and a half. We work every day except on Saturdays, which is our weekly day off. Fieldwork begins at nine o'clock when we arrive at the site. In this campaign in the Sierra de Atapuerca eight sites have been excavated simultaneously (Trinchera del Elefante, the Gallery, Gran Dolina, Portalón, Gallery of Statues, Sima de los Huesos, Cueva del Mirador and Fuente Mudarra). Each of them has a team of diggers and except for certain peculiarities, the methodology is the same in all. As an example, let's imagine we are digging at the site of Gran Dolina at the TD10-3 level. We'll see that the excavation surface is divided into square meters marked on the sediment with a grid made out of rubber cord. To identify each of the squares we use a system of letters and numbers, where the vertical axis is represented by numbers and the horizontal axis by letters. Today, we will work on square N19. Each square is dug by one or two excavators (who may be archaeologists, palaeontologists, geologists or paleoanthropologists). The basic toolkit for each excavator consists of a hammer and a screwdriver to remove sediment slowly, a brush and a dustpan to sweep and remove sediment, which is then poured into a bucket.

 

Furthermore, depending on the hardness of the sediment we may have to use a chisel, a hammer, a pick... As excavation progresses, dental and bone remains of a variety of animals and stone tools made of different raw materials appear. The remains that appear cannot be just collected and taken away, we must document the exact location at which they appeared. Removing the sediment that fills the caves and has buried and protected these archaeological remains for thousands of years involves the destruction of the site. For this reason it is very important to document exactly where and in what conditions each piece was found, i.e. collect their exact coordinates. The lower left corner of each square is represented by the coordinates 0,0, in which the horizontal axis is the X and the vertical axis is the Y. Let's say we have found a quartzite flake in our N19 square. We'll record how far it is from X and Y by measuring the distance from the axis. Another useful detail is the depth at which it is located with regards to a 0 point set at the original level of the surface when we began to excavate the site. Depth is represented by Z in the coordinate system. For Z, we measure the height with a laser level and a surveying rod. Until recently, this process was done manually and it was transcribed into record sheets assigned to each square.

 

However, technology has made this process faster and more convenient. Nowadays, paper record sheets have been replaced by PDAs (personal digital assistants) with specific software that allows us to enter all these data for all the retrieved records. Recording coordinates (X, Y, Z) is automated. We use a laser sight connected to a total station that detects the square and the exact coordinates when we place it next to the object we want to register and activate a command from our PDA. Once we have these data, we must introduce the orientation of the piece according to a theoretical North. At the site of the Gran Dolina, it's been established in the section which would correspond to the geographical East. Finally, we record the piece's measures: the length, width and thickness of the quartzite flake. Once all the data has been collected, it is sent to a central computer at the site. Only then can we pick up the quartzite flake and place it in a sealable bag on which we have stuck a label (printed at the site itself, after sending the data to the central computer). The label of this quartzite flake indicates that we have recovered it in the 2013 campaign, at the site of the Gran Dolina, level TD10-3, square N19. It was at a depth of 400 cm from level 0, and it is the 57th record retrieved this year in this square. The location and orientation data of the pieces will be useful to understand how the site was formed, but it will also help to establish the role each area of the cave had when it was inhabited by hominids. Hence the importance of documenting everything as accurately as possible. Once the piece is collected, we continue digging. As we remove sediment, we deposit it in the bucket we have been assigned. Once it's full, the sediment is not thrown away. The bucket is emptied into a bag in which we introduce a label with data of the site, the square and the depth interval at which we are digging. That bag with sediment, along with all the others, is washed and sieved in the Arlanzón River. Micromammal bones and teeth that are too small to be recovered in normal digging remain trapped in the sediment. Micromammals provide valuable information that helps both environmental reconstruction as well as the dating of archaeological levels. At the end of an excavation day, all material recovered that day is deposited into boxes that are taken to the laboratory. The work process in the laboratory, however, has its own methodology, which would make for another post.