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1. Case studies and archaeological feedback

Archaeological Feedback on Geophysical Research in the Netherlands Through Case Studies Using Excavation Data

Gerbrand Beenen et Joep Orbons
p. 23-26

Résumé

– Revisiting geophysical results post-excavation can lead to additional information.

– Giving geophysicists feedback on their interpretations can lead to valuable insights.

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Texte intégral

1Currently in the Netherlands, archaeological data about a surveyed site is used fairly linearly in practice. The process usually starts with a desktop study, followed by augering or geophysics and finally trial trenches or excavation. Using ARCHIS (a nation-wide archaeological information system in the Netherlands), the excavator checks for any prior archaeological investigations in this area and will use this information to choose where to excavate within the research area. Trenches are likely to be dug in places where the geophysical report shows a possible archaeological feature. However, feedback on data interpretation seldom reaches the geophysicists after the excavation is completed. This is a serious drawback because without information evaluating the interpretation of geophysical data in specific cases, the geophysicist cannot learn to identify the flaws in his interpretation and this will affect the accuracy of his predictions in the future. Secondly, earlier research is not revisited post-excavation. While excavations lead to more information than geophysics, it is relatively common that sites are not fully explored archaeologically even of prospection has covered the entire known area. Interpreting prospection data can be quite a challenge and potential archaeological features can easily be missed on primary inspection of the data. Using excavation results to help interpret archaeological features in the prospection data can lead to more archaeological information in certain cases but this ‘extra step’ is rarely taken.

2The presented research focuses on investigating these two drawbacks using case studies. First, the accuracy of the prospector’s interpretation is tested by comparing it to the excavation data. With many case studies combined, this research hopes to find patterns in incorrect interpretations, so researchers in the geophysical field can learn from these and perform more accurate predictions in the future. Second, this study attempts to acquire new archaeological information by combining the data of both the geophysical survey and the excavation. This is done by plotting them in a GIS and analyzing which archaeological features from the excavation data continue in the geophysical data. Although newly acquired archaeological information is a great bonus, the goal of this part of the study is to show that revisiting prospection data post-excavation can contribute added archaeological value.

3A case study of a site close to the city of Brielle is used as an example in this presentation. Desktop queries suggested walls and a ditch on the north side of the field, which were expected to be parts of a monastery (Exaltus & Orbons, 2018, p. 6). An EMI and magnetometer survey was followed with augering the detected anomalies. The results and interpretation of this research is given in Figure 1.

Figure 1. The left and middle picture show the original magnetic and EMI 100 cm results and the right picture shows the combined interpretations of the EMI and magnetometer surveys on top of the EMI 100 cm results. Some interpretations are not shown for image clarity (using data from the ArcheoPro database and Exaltus & Orbons, 2018, pp. 16 & 19, Figs 7 & 9).

Figure 1. The left and middle picture show the original magnetic and EMI 100 cm results and the right picture shows the combined interpretations of the EMI and magnetometer surveys on top of the EMI 100 cm results. Some interpretations are not shown for image clarity (using data from the ArcheoPro database and Exaltus & Orbons, 2018, pp. 16 & 19, Figs 7 & 9).

4About a year later, an excavation was carried out by a different archaeological company that excavated three small trenches, one of which cut directly across archaeological features found in the geophysical survey. After the excavation was completed, they reported their interpretation of the research which can be seen in Figure 2 (Cornelisse, 2019: 29, 37-38). The area with ‘potential archaeology’ in this figure is based on the excavated trenches, with no further regard for the geophysical results (Cornelisse, 2019: 29, 38). The information flow stops at this point.

Figure 2. Interpretation of the excavation report: the blue dotted line is the maximum southward extension of the monastery ditch, the pink area reveals no archaeology, and the red area signifies potential archaeological features (Cornelisse, 2019, p. 38, Fig. 8.1).

Figure 2. Interpretation of the excavation report: the blue dotted line is the maximum southward extension of the monastery ditch, the pink area reveals no archaeology, and the red area signifies potential archaeological features (Cornelisse, 2019, p. 38, Fig. 8.1).

5In my research, this is where I start to look at the archaeological feedback first by comparing geophysical interpretations with the excavated results. In the presented case study, the walls interpreted in the EM results lines up with the excavated features and most of the magnetometer walls are just outside of the excavated trench, so they cannot be tested. Secondly, the geophysical results are re-evaluated using the primary data from the geophysical report and the excavated archaeological features. With this data, the wall and ditch features from the monastery can be extended, as shown in Figure 3. After some additional analysis, the walls interpreted from the magnetometer results seem to line up with the ditch extension, suggesting that the fill of this ditch contained a magnetic component and leading to the hypothesis that the ditch was misinterpreted as a wall. This could be useful information to keep in mind for future geophysical research dealing with potential ditches.

Figure 3. Reevaluation of the combined geophysical data and excavated results (using data from Exaltus & Orbons, 2018, p. 16, fig. 7 and Cornelisse, 2019, p. 21, fig. 4.2).

Figure 3. Reevaluation of the combined geophysical data and excavated results (using data from Exaltus & Orbons, 2018, p. 16, fig. 7 and Cornelisse, 2019, p. 21, fig. 4.2).

6The case-study demonstrates direct use of geophysical results to place archaeological trenches, but no revisiting post-excavation. A reevaluation could have led to a more realistic interpretation, being based on abundant complementary geophysical data rather than the absence of archaeological remains in the other two trenches.

7In conclusion, post-excavation reevaluation of geophysical data can provide useful information that can be useful to the geophysical surveyors interpreting the data, leading to more and better insights and more accurate interpretations. This particular case study illustrates well what this feedback is about. The other case-studies provided relatively poorer results, with testing and reevaluation leading to no new insights or a better archaeological understanding.

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Bibliographie

ArcheoPro Database. Not publicly available. Eijsden: ArcheoPro.

Cornelisse, H. 2019. Het Regulierenklooster bij Brielle: Een inventariserend veldonderzoek door middel van proefsleuven (IVO-p). Archol Rapport 440.

Exaltus, R. & Orbons, P.J. 2018. Twee Getuigen, Brielle, Gemeente Brielle: Inventariserend Veldonderzoek (IVO-O); Geofysisch onderzoek met controleboringen. Eijsden: ArcheoPro. ArcheoPro Rapport 17083.

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Table des illustrations

Titre Figure 1. The left and middle picture show the original magnetic and EMI 100 cm results and the right picture shows the combined interpretations of the EMI and magnetometer surveys on top of the EMI 100 cm results. Some interpretations are not shown for image clarity (using data from the ArcheoPro database and Exaltus & Orbons, 2018, pp. 16 & 19, Figs 7 & 9).
URL http://journals.openedition.org/archeosciences/docannexe/image/8149/img-1.jpg
Fichier image/jpeg, 4,8M
Titre Figure 2. Interpretation of the excavation report: the blue dotted line is the maximum southward extension of the monastery ditch, the pink area reveals no archaeology, and the red area signifies potential archaeological features (Cornelisse, 2019, p. 38, Fig. 8.1).
URL http://journals.openedition.org/archeosciences/docannexe/image/8149/img-2.jpg
Fichier image/jpeg, 6,5M
Titre Figure 3. Reevaluation of the combined geophysical data and excavated results (using data from Exaltus & Orbons, 2018, p. 16, fig. 7 and Cornelisse, 2019, p. 21, fig. 4.2).
URL http://journals.openedition.org/archeosciences/docannexe/image/8149/img-3.jpg
Fichier image/jpeg, 2,3M
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Pour citer cet article

Référence papier

Gerbrand Beenen et Joep Orbons, « Archaeological Feedback on Geophysical Research in the Netherlands Through Case Studies Using Excavation Data »ArcheoSciences, 45-1 | 2021, 23-26.

Référence électronique

Gerbrand Beenen et Joep Orbons, « Archaeological Feedback on Geophysical Research in the Netherlands Through Case Studies Using Excavation Data »ArcheoSciences [En ligne], 45-1 | 2021, mis en ligne le 16 août 2021, consulté le 29 janvier 2023. URL : http://journals.openedition.org/archeosciences/8149 ; DOI : https://doi.org/10.4000/archeosciences.8149

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Auteurs

Gerbrand Beenen

Corresponding author, student MA Archaeology at the University of Groningen, The Netherlands, Schoolstraat 13, 8441 AV Heerenveen, The NetherlandsSupervisor, senior specialist in geophysical research and senior archaeologist at ArcheoPro. St Jozefstraat 45, 6245 LL Eijsden, The Netherlands

Joep Orbons

Supervisor, senior specialist in geophysical research and senior archaeologist at ArcheoPro. St Jozefstraat 45, 6245 LL Eijsden, The Netherlands

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