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Geoarchaeology of the early medieval stronghold surroundings in grzybowo near Września, Greater Poland

Michał Marcinkowski
Michał Marcinkowski
 and 
Małgorzata Szczepaniak
Małgorzata Szczepaniak
   | Sep 10, 2019
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Published Online: Sep 10, 2019
Page range: 95 - 108
Received: Mar 14, 2019
DOI: https://doi.org/10.2478/quageo-2019-0032
© 2019 Michał Marcinkowski, Małgorzata Szczepaniak published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

Fig. 1

Location of the study area with marked location of boreholes, cross-section lines of the stronghold area, and archaeological excavation (profile 47).
Location of the study area with marked location of boreholes, cross-section lines of the stronghold area, and archaeological excavation (profile 47).

Fig. 2

Amount of precipitation and temperature anomalies in the Middle Ages after Büntgen et al. (2011) – simplified.
Amount of precipitation and temperature anomalies in the Middle Ages after Büntgen et al. (2011) – simplified.

Fig. 3

Fragment of the geomorphological map of Greater Poland after Karczewski et al. (2007), changed.
Fragment of the geomorphological map of Greater Poland after Karczewski et al. (2007), changed.

Fig. 4

View of the stronghold. a) lowering in the embankments, b) view to the west of the stronghold with marked cross-section line A-A` exceeding the boundary of the embankments.
View of the stronghold. a) lowering in the embankments, b) view to the west of the stronghold with marked cross-section line A-A` exceeding the boundary of the embankments.

Fig. 5

Geological cross sections around the stronghold. a) fragment of the profile A-A`, b) fragment of the profile B-B`, c) profile C-C`, d) profile D-D`.
Geological cross sections around the stronghold. a) fragment of the profile A-A`, b) fragment of the profile B-B`, c) profile C-C`, d) profile D-D`.

Fig. 6

Calibration of radiocarbon data set in graphical form.
Calibration of radiocarbon data set in graphical form.

Fig. 7

Profile of archaeological section 47 according to Petri and Bakiewicz (2002, simplified), with a visible outline of a river bed filled with dark-brown sediments.1 – clay with humic admixtures, 2 – sandy clay, 3 – sand with artefacts, 4 – sand with humus, 5 – dark brown sand, 6 – humic sand (described by archaeologist as an arable layer).
Profile of archaeological section 47 according to Petri and Bakiewicz (2002, simplified), with a visible outline of a river bed filled with dark-brown sediments.1 – clay with humic admixtures, 2 – sandy clay, 3 – sand with artefacts, 4 – sand with humus, 5 – dark brown sand, 6 – humic sand (described by archaeologist as an arable layer).

Fig. 8

Proposal of the reconstruction of subsequent stages of the change in the location of the Struga River channel based on geological research, stages of development of the stronghold according to archaeological research results (Petri 2006, Petri, Bakiewicz 2002).a) and b) the older phase of the ring fort, c) younger phase with visible marked older phase, d) the younger phase of the ring fort; archaeological excavation no. 47 marked by a red colour.
Proposal of the reconstruction of subsequent stages of the change in the location of the Struga River channel based on geological research, stages of development of the stronghold according to archaeological research results (Petri 2006, Petri, Bakiewicz 2002).a) and b) the older phase of the ring fort, c) younger phase with visible marked older phase, d) the younger phase of the ring fort; archaeological excavation no. 47 marked by a red colour.

Loss on ignition analysis of different samples with visible organic matter.

Borehole No.Depth [cm]Ignition loss [%]Sediment
140–607.91Fine-grained sand
4120–1504.95Sandy clay
4245–26011.04Fine-grained sand
4293–30019.11Sandy silt
4300–31047.27Peat
4330–35021.35Gyttja
8150–1801.64Clayey sand
1050–703.50Clay
1220–402.91Fine-grained sand
1925–409.69Gravel mix
19130–15010.85Medium-grained sand
25205–2202.56Clay
25220–26031.09Find-grained sand with organic

Content of CaCO 3 in particular samples.

Borehole No.Depth of the sample [cm]Content of CaCO3 [%]Sediments
4330–35022Gyttja
24075–10014Clay
2950–8514Clayey sand
31110–1306Clayey sand
3350–7010Sandy clay
3435–559Sandy clay
3855–7011Sandy silt
39085–1009Sandy silt
39185–200<5Sandy silt
40075–1009Sandy silt

Calibration of radiocarbon data set; made with OxCal v4.2.4 (Bronk Ramsey 2013) and IntCal13 atmospheric curve (Reimer et al. 2013).

Sample no./ borehole no./ depthLab. codeLab. commentsMaterial14C age BPAge after calibration 68% [BC]Age after calibration 95% [BC]
Grzybowo 1/ otw4/ 310 cmPoz-56565Date out of range – 50,000±3,000 BPwood50,000±3,000 BP52,769 BC (68.2%) 45,099 BC61,269 BC (95.4%) 43,298 BC
Grzybowo otw25/ 2/ 220–260 cmPoz-56607Date out of range – 51,000 BPorganic fragments from sand>51,000 BP(68.249,052 %) 49,051 BC BC(95.449,052 %) 49,051 BC BC

Results of the sieve and aerometric analysis for 144 samples from boreholes Nos. 1 to 40.

SedimentsNumber of the samples
1Fine-grained sand62 samples
2Medium-grained sand25 samples
3Coarse-grained sand2 samples
4Clayey sand5 samples
5Sandy clay14 samples
6Compact clay5 samples
7Clay3 samples
8Sandy silt3 samples
9Gravel mix14 samples
10Clayey gravel11 samples
eISSN:
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Language:
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