Fig 1.
Map of Southern Germany with the included archaeological sites, outcrops of Jurassic and Tertiary chert.
Basemap: © European Union, Copernicus Land Monitoring Service 2020, European Environment Agency (EEA)", f.ex. in 2018: “© European Union, Copernicus Land Monitoring Service 2018, European Environment Agency (EEA)”, with funding by the European Union.
Fig 2.
Chert from the three outcrops considered in this study.
1. Blaubeuren Blauberg, 2. Abensberg Arnhofen, 3. Randecker Maar. Photos taken by B. Schürch.
Table 1.
Geological samples analysed.
Fig 3.
1, 2 Jurassic cherts from Vogelherd, 3, 4 Tertiary cherts from Vogelherd, 5, 6 Tertiary cherts from Randecker Maar. Classifications based on macroscopic criteria. Photos by B. Schürch.
Fig 4.
Example spectra of the three raw material outcrops tested.
Fig 5.
PCA scatter plot (covariance matrix) resulting from the first derivative data of these spectra (left) and the loading plot showing the direction different variables (in our case different wave numbers) plot in the PCA biplot and first two principal components (top right); and the eigenvalue (right bottom).
All archaeological samples from the Randecker Maar were macroscopically predicted to be Tertiary chert, these are shown as orange triangles. The samples from Vogelherd predicted to be Tertiary chert by macroscopical analysis are shown as black triangles. The samples predicted to be Jurassic chert from Vogelherd are shown as black diamonds.
Fig 6.
The three groups are coloured in green, blue and red. Archaeological samples are black and orange and were not predefined to a group. The black ellipses encompass 50% of the samples of each group.
Table 2.
LDA predictions (discriminant-scores) of the geological samples.
Table 3.
Summary of the predictions of the macroscopic analysis and the predictions of the LDA.
Table 4.
Summary of the LDA accuracy tests.