Arjan Louwen, Cristian van der Linde, Marieke Doorenbosch & Hans Huisman
5.5 Palynological research (Marieke Doorenbosch)
5.5.1 Palynological analysis of the
Wieselseweg barrows
Pollen analysis is a tried and tested method for creating vegetation reconstructions of the surroundings of barrows (Casparie/Groenman-van Waateringe 1980; Doorenbosch 2013a; Van Zeist 1967; Waterbolk 1954). Palynological research can shed light on the question of how a landscape appeared prior to the erection of a barrow or the creation of a new mound phase. Based on these questions the Wieselseweg barrows were sampled for palynological analysis. As part of the Ancestral Mounds project, two barrows at Echoput, some 2 kilometres southwest of the Wieselseweg mounds, were excavated earlier (Fontijn
et al. 2011). These two Middle Iron Age barrows were
palynologically investigated and the results show that these mounds lay in an already old heath, which was probably maintained through grazing. Palynological analysis of other barrows on the Veluwe showed similar results regarding the barrow landscape (Doorenbosch 2011; 2013ab). Most analysed barrows in this area, however, date to the Late Neolithic (not including the Echoput Middle Iron Age mounds). As information regarding the Veluwe barrow landscape during the Bronze Age is currently lacking, researching the Wieselseweg barrows, which date to the Middle Bronze Age A, was expected to provide new insights.
5.5.2 Material and methods
Pollen samples were taken at various locations in and under the mounds. To gain an impression of the vegetation in the period before and at the time of the construction of the barrows, a vertical series of ten sequential samples was taken from the soil profiles of all mounds, where by the fifth sample most likely was taken from the old surface. To this
Sample location Sample name
Mound 1 Profile West Soil profile series 1-10: 5
S 14, cremation MP S14 S 15, brown fill MP S15 Level 11 S 54 VNR 601 VNR 626 Level 11, Profile 2 S 56 VNR 743 Level 11, Profile 2 S 72 VNR 770
Mound 2 Profile Soil profile series 1-10: 5
Level 51 S 14 VNR 689
S 21 VNR 690
Level 52 S 26 VNR 789
Mound 3 Profile west Soil profile series 1-10: 5
Level 5-6 S 6 MP S6 Level 6 S 15 VNR 619 S 17 VNR 683 Level 8 S 25 VNR 684 VNR 687 VNR 688 Tab. 5.3: Overview of the pollen samples taken. The
not completely unsusceptible to degradation. Pollen preserves best in waterlogged, so anaerobe, conditions. Under aerobe conditions the pollen grains are subject to oxidation, which can cause the wall of the pollen grain to become thinner (Havinga 1964). Biological activity, such as bacterial degradation, likely plays a role in these circumstances (Havinga 1967; 1984). Pollen can also be mechanically affected during transport (Holloway 1989). When pollen rains down on the surface of a mineral soil, it will be subject to corrosion and partially wash out. Most of the time there will be a balance between the supply of pollen and its disappearance, and pollen present in the top layer of the soil will be representative of the vegetation in the surroundings.
Pollen is frequently present in the soil in and under barrows. As the barrow was built on the old surface upon which the pollen rained down, the soil is closed off from the air. This causes less oxygen to reach it and the biological activity to decrease, making the pollen grains less accessible to corrosion. The odds of pollen being washed out also decrease. That pollen is not always present in the soil under a barrow, was demonstrated by the palynological research conducted at the Wieselseweg.
The reason why pollen was not preserved remains unclear. As was noted in the introduction, the Echoput mounds did contain pollen, in contrast to those of the Wieselseweg. Yet circumstances were not all that different from those at the Wieselseweg.
The texture of the soil might offer a possible explanation. Even though the soils under both mounds were classified as Holtpodzols (gY30, see the soil map of the Netherlands), pedologist J. Boerma classified the soils used to construct the Echoput mounds as loamier than that used to create the Wieselseweg mounds. Moreover, the podzol underneath the Wieselseweg mounds, in contrast to the podzol under the Echoput barrows, was hardly recognizable. It is possible that the soil used to erect the Wieselseweg mounds was a slightly coarser sediment than that of the Echoput mounds, causing a better aeration of the soil and the pollen grains of the former to have been exposed to oxidation more quickly. In addition, the pollen grains could have been washed out easier due to the higher permeability of the soil. In order to test this hypothesis, eight samples were selected at each location for grain size analysis. In addition to the already mentioned location, an additional four samples with well-preserved pollen from a barrow from an entirely different location, Mound 7 of the Oss-Zevenbergen barrow group (Bakels/Achterkamp 2013; Doorenbosch 2013a, tab. 12.1), were also subjected to grain size analysis (see Tab. 5.4 for a complete overview). The analysis was conducted in the laboratory for sediment analysis of the VU University Amsterdam with a Laser Particle Sizer Helos KR Sympatec.
Figure 5.17 shows a summary of the results. In this figure the density distribution of all samples is shown plotted against grain size. In order to compare the results in detail, the percentages per classification of the three locations were compared. The results of this are shown in Table 5.5a/b.
As can be seen in Figure 5.17 and Table 5.5a, the differences between Wieselseweg and Echoput in particular are very low. This can also be seen in Table 5.5b, which shows that there were no significant differences between the two locations, with exception of the medium coarse sand fraction. There are significant differences between Oss-Zevenbergen and the other two sites in almost all fractions. The sediment of which the Oss-Zevenbergen barrow consists is primarily fine sand, while the sediments from the other two sites mainly consist of medium coarse and coarse sand. The finer composition of the sediment of the Oss-Zevenbergen barrow could have contributed to the good pollen conservation. However, this cannot explain the differences in conservation between the Wieselseweg and Echoput, and other avenues have to be explored for an explanation. One possibility is that the
No. Location Mound Sample
location Sample name
1 Echoput Mound 1 Sod 1 MT 266
2 Sod 2 MT 267
3 Old surface 1 MT 268
4 Old surface 2 MT 269
5 Mound 2 Sod 1 VNR 99
6 Sod 2 VNR 100
7 Old surface 1 A2.1 old surface 2
8 Old surface 2 A2.1 old surface 1
9 Wieselseweg Mound 1 (T 101) Profile west Sample 1
10 Sample 5
11 Mound 2 (T 201) Profile west Sample 1
12 Sample 5
13 Mound 3 (T 301) MT 801
14 MT 802
15 MT 803
16 MT 804
17 Oss-Zevenbergen Mound 7 Sod 1 VNR 275
18 Sod 2 VNR 276
19 Sod 3 VNR 277
20 Sod 4 VNR 279
Tab. 5.4: Overview of the samples analysed on grain size
soil of the Wieselseweg is reasonably dry in comparison with that of the Echoput, where the environment is more humid (Fontijn 2011, 30). The subsoil in which the Echoput mounds are situated contains loam, which is not the case for the Wieselseweg subsoil. This difference, however, does not come to the fore in the grain size analysis. It is possible that the loam by the Echoput is located deeper in the subsoil and that this causes it to retain moisture. These more humid, more anaerobe conditions could contribute to the better preservation of the pollen in the Echoput subsoil, while the Wieselseweg subsoil plays host to a stronger disintegration of organic material, including pollen. The Oss-Zevenbergen subsoil is also dry, but at the
same time poorer in nutrients, causing a lower degree of microbiological activity.
5.5.5 Conclusion
Unfortunately, the absence of pollen in the samples from the Wieselseweg barrows made it impossible to make a vegetation reconstruction of the surroundings. This in contrast to the nearby Echoput location, where previous research had established that the soil under these barrows did contain pollen. The additional research conducted to determine whether the absence or presence of pollen could be explained by any difference in sediment texture unfortunately offered no conclusive results.
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.55 0.60 0.65 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 1.15 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 1.95 2.00 2.05 2.10 2.15 Density distribution q3 * 0.1 0.2 0.4 0.6 0.81.0 2 4 6 8 10 20 40 60 80100 200 400 6008001000 2000 4000 Particle size / µm
Echoput Mound 1 Sod 1 MT 266
Echoput Mound 1 Old surface 1 MT 268
Echoput Mound 1 Sod 2 MT 267
Echoput Mound 1 Old surface 2 MT 269
Echoput Mound 2 Sod 1 VNR 99
Echoput Mound 2 Sod 2 VNR 100
Echoput Mound 2 Old surface 1
Echoput Mound 2 Old surface 2
WW Mound 1 Profile section west Sample 1
WW Mound 1 Profile section west Sample 5
WW Mound 2 Profile section west Sample 1
WW Mound 2 Profile section west Sample 5
WW Mound 3 MT 801
WW Mound 3 MT 802
WW Mound 3 MT 803
WW Mound 3 MT 804
Oss-Z Mound 7 VNR 275
Oss-Z Mound 7 Sod 2 VNR 276
Oss-Z Mound 7 Sod 3 VNR 277
Oss-Z Mound 7 Sod 4 VNR 279
Location Barrow Sample location Sample name
Fig. 5.17: Results of the grain size analysis. The density distribution q3 is plotted against the particle size (µm) (after
% Clay (<8 µm) % Very fine silt (8‑16 µm) % Fine silt (<16-32 µm) % Coarse Silt (32-63 µm)
AWW Echoput Oss-Z AWW Echoput Oss-Z AWW Echoput Oss-Z AWW Echoput Oss-Z
7.82 6.69 2.56 2.60 2.67 1.23 4.07 4.40 1.48 8.82 8.37 1.90 6.71 5.10 2.67 2.28 1.82 1.33 3.50 2.81 1.84 7.65 5.73 2.52 5.59 6.72 1.75 1.96 2.71 0.81 3.06 4.26 1.02 6.16 7.32 1.33 2.08 6.45 6.83 1.72 2.18 2.69 1.36 3.28 4.14 2.06 6.65 8.01 8.12 5.11 2.55 1.93 3.36 2.88 6.48 5.58 7.93 4.79 2.47 1.84 3.20 2.73 6.57 5.11 6.57 5.98 2.15 2.42 3.08 3.65 6.48 6.81 1.94 4.05 0.78 1.59 1.03 2.38 1.37 4.43
% Very fine sand (63‑125µm) % Fine sand (125-250µm) % Medium coarse sand (250-500µm) % Course sand (500-1000µm)
AWW Echoput Oss-Z AWW Echoput Oss-Z AWW Echoput Oss-Z AWW Echoput Oss-Z
10.76 8.59 6.73 13.35 8.90 43.40 28.93 23.16 38.86 22.89 33.11 3.83 9.05 6.50 6.95 9.90 8.31 35.67 24.18 25.85 38.35 30.56 36.44 10.56 7.56 7.61 6.05 11.45 10.67 46.32 30.61 28.51 39.00 31.85 30.32 3.71 8.21 9.22 5.82 12.61 12.77 42.44 30.63 25.13 40.86 28.97 27.73 3.67 8.23 6.22 18.38 7.43 34.18 19.13 18.23 34.74 8.16 5.77 13.86 7.63 33.51 20.40 23.59 36.18 8.42 7.62 14.06 8.79 32.66 20.94 24.57 34.49 1.81 4.84 4.95 5.24 19.05 15.14 51.14 38.17
% Very coarse sand (1000-2000µm)
AWW Echoput Oss-Z
0.75 4.12 0 6.16 7.45 0.11 1.77 1.88 0 1.02 3.49 0 0.48 16.97 0.72 15.55 2.03 9.31 17.93 24.16
Tab. 5.5a: Results of the grain size
analysis in percentages per grain size (after Doorenbosch 2013a, tab. 5.4a).
C Echoput Oss VFSi Echoput Oss FSi Echoput Oss
AWW x *** AWW x *** AWW x *
Echoput *** Echo *** Echo **
CSi Echoput Oss VFSa Echoput Oss FSa Echoput Oss
AWW x *** AWW x x AWW x ***
Echoput *** Echo x Echo ***
MCSa Echoput Oss CSa Echo Oss VCSa Echoput Oss
AWW * *** AWW x ** AWW x x
Echoput **** Echoput **** Echoput **
Tab. 5.5b: Results of the statistical
analysis (tested with an unpaired t-test) of the results of the grain size. X: ‘not significantly different’; *: significantly different (p<0.05); ** significantly different (p<0.01); *** significantly different (p<0.001); ****: significantly different (p<0.0001). Table after Doorenbosch 2013a, tab. 5.4b.