SGS Berlin & Potsdam - University of Bucharest SEG Student Chapter Joint Field Camp 2009
The SEG Foundation Field Camp program made it possible that two students of the University of Bucharest SEG Student Chapter (UB) and seven students from the SEG Student Chapter of the Student Geoscientific Society Berlin & Potsdam at Freie Universitaet Berlin (SGS) were able to attend a joint field camp of both Student Chapter that was organized by the officers of the SGS. The two participants from the UB SEG Student Chapter as well as one participant of the SGS Berlin & Potsdam attended the previous Romanian-German Joint Field Camp in 2008. Their experiences and knowledge were of great profit for all participants of this project.
The focus of this joint field camp was the application of near surface geophysical methods in order to resolve archaeological targets at a site in the south of Berlin. Therefore the project organiser established contact to professionals from the Prehistoric and Protohistoric Archaeological department of the Freie Universitaet Berlin. They recommended an archaeological site in the South of Berlin which is for great interest to the archaeologists. Their investigations concentrate on the amount and structure of the production and treatment of iron as well as its integration in the settlement structure during the pre-Roman Iron Age. The target consists of slag as a waste product of iron-smelting on the one hand and on leftovers of smelting furnaces on the other hand. Even though the archaeological exploration of this region is pretty incomplete, the findings of slag and objects made of iron could be dated back to 450 years BC. These findings only proof the utilization of iron at that time but not the production. The production is dated back to 150/100 years BC by the finding of smelting furnaces. Nevertheless, in the south of Berlin findings of smelting furnaces proof that the production of iron in this particular region can be dated back to about 300 years BC. This leads to the assumption that the process of iron smelting is longer known in this region as expected. In order to resolve these targets two near surface geophysical methods have been used: Geomagnetics and Geoelectrics. In addition, the idea behind this project was to offer unexperienced students the possibility to train their skills in acquisition and processing techniques.
The landscape in the south of Berlin is called "Teltow Plateau" and was formed during the iceage 20.000 years ago. The altitude of this plateau ranges between 45 and 60 m above sealevel. The landscape is characterized by ground morains that were originated by the forward motion of the continental icesheet. Thus, the basement is composed of glacial loams that consits of gravel, sand, silt and clay. These sediments were directly deposited in front of the continental icesheet. The investigation site was on an area of arable land where six 30x30 meter grids were defined.
Geomagnetics - The main target at this field camp were near surface archaeological structures from metallurgical processes. For the magnetics measurements a single axis magnetic gradiometer was used. It has two fluxgate gradient sensors with a 1m separation between the sensing elements. These instruments measure the vector-component of the magnetic field parallel to the direction of their magnetic axes. They have a high temperature stability which ensures a minimal drift of the sensors during the survey resulting in a reduced need for adjustment. Due to the usage of two sensors the instrument measures two lines of data during each traverse. Before setting up any measurements it was ensured that the operator was free of magnetic materials. In order to obtain precise gradiometer measurements both sensors had to be calibrated. Therefore a very low gradiometer environment was selected to match the offset and gain as well as the exact alignment of both sensors.
Geoelectrics - After having a first look to our geomagnetic maps, it was possible to localize some significant anomalies, but only in plane view. In order to get real 3D locations of this anomalies it was necessary to get some information about the depth. Therefor the Direct Current Resistivity method (DCR) was used. In contrast to geomagnetical measurements, working with the natural potential field, DCR methods are active methods, measuring the potential difference of an artificial electrical field. This field is generated by inducing current into the underground via two electrodes. The underground can be interpreted as a resistor and its resistance depends upon geometry and material properties. Thus, the specific resistivity of the material in the underground is what is interesting to know, because it directly reflects if there is a good (low resistivity) or a bad (high resistivity) conductor. The geoelectrical target is not homogenous, since it was searched for archaeological heterogeneities. Whereas the measured resistivity is independent to the geometry in a homogenous earth, it becomes dependent in a heterogenous one. Furthermore, the resistivity is a function of the material properties of the different heterogeneities. That is why the measuring personnel had to deal with an apparent resistivity. For processing the software “RES2DINV” has been used.
The investigations on the archaeological target were accomplished by geomagnetic and geoelectric measurements on six 30x30 meter grids. The geomagnetic data delivered strong anomalies on grid 1 and 2 and smaller anomalies on grid 5 and grid 6 as well. The measurments on grid 3 and grid 4 delivered no considerable anomalies. It is supposable that the big anomalies on grid 1 and grid 2 may be some leftovers of smelting furnaces or big accumulations of slag. The smaller anomalies could be indicators for several smaller slag pieces. The results of the geoelectrical measurements confirmed the big anomalies on grid 1 and grid 2. These anomalies could be located to depth of about 1 to 2 meters. The geoelectric anomalies on grid 2 were not that good developed as the ones on grid 1 but still clearly observeable. The project was a great opportunity to train geophysical field work. Every participant was able to skill the knowledge in data acquisition and processing.
- Gutjahr, S., Hummel, N., Stuermer, K. (2009): Freie Universitaet Berlin and University of Bucharest Summer Field Camp 2009 Report.
- University of Bucharest SEG Student Chapter - SGS Berlin & Potsdam Joint Field Camp 2008
- SGS Berlin & Potsdam High School Field Camp 2011
- SGS Berlin & Potsdam - University of Indonesia Geophysical Society Joint Field Camp 2012
- Institute of Applied Physics Nizhny Novgorod - SGS Berlin & Potsdam Joint Field Camp 2014
Personal experience written by a Field Camp participant