Pollen analysis of samples from the defensive ditch (vollgrav) at Site FO4 Klypen-Øst, Follobanen, Oslo

RAPPORT nr. 2017-001

Pollen analysis of samples from the defensive ditch (vollgrav) at Site FO4

Klypen-Øst, Follobanen, Oslo

Philip Buckland and Jan-Erik Wallin

INSTITUTIONEN FÖR IDÈ- OCH SAMHÄLLSSTUDIER

MILJÖARKEOLOGISKA LABORATORIET

Pollen analysis of samples from the defensive ditch (vollgrav) at Site FO4 Klypen-Øst, Follobanen, Oslo

Philip Buckland¹ and Jan-Erik Wallin²

1The Environmental Archaeology Lab, Umeå University, Sweden

2Pollenlaboratoriet i Umeå AB, Sweden

Background

Nine samples were submitted for pollen analyses from three profiles from the "Vollgrav"

defensive ditch feature, at the Follobanen FO4 Klypen-Øst excavation in Oslo. These samples were investigated with respect to their pollen contents and, in a separate investigation, soil micromorphology. The micromorphological methods and results are described in detail in a separate report from Richard Macphail (2016). Where relevant, these findings are commented on with respect to the other analysis results below.

Methods

Sampling

Sampling was undertaken by archaeological staff in connection with the excavation process.

Pollen analyses

Samples were treated according the standard methodology for pollen preparation as described by Moore et al. 1991. The concentrated pollen was placed on a slide and coloured with saffron-dyed glycerine. Pollen taxa were identified under microscope using the keys of Beug (1961) and Moore et al. (1991), counted, and summarised as standard pollen percentage diagrams for this report. Carbon particles (>25 µm) were also counted and included in two of the pollen diagrams.

When analysing pollen from soil samples, there is a risk of the overrepresentation of taxa producing thick-walled pollen grains (e.g. flowers of the Compositae family); the thicker walls reducing their susceptibility to decay with respect to other taxa. A number of thick- walled taxa were found at relatively high abundance in this project (e.g. flowers in the Compositae, Chenopodioideae and Vicia families). However, due to the high abundance of pollen of other species, the results are considered reliable.

Pollen interpretation

Percentage pollen diagrams are used to illustrate the relative proportion of different pollen taxa in each sample. Pollen taxa are not always equivalent to a specific species or family of plants. They may sometimes represent a group of plants with indistinguishable fossil pollen, and thus a lower taxonomic resolution than may often be obtained from plant macrofossil analyses. The taxonomic resolution used in this report allows for the identification of groups representing different landscape communities of archaeological interest (see Table 2).

Results

The pollen diagrams presented here (Figure 3-4) show the depth of the sample and sample number on the y-axis, and relative proportion of each pollen taxa on the x-axis. It is praxis in palynology to use a filled curve to join the percentage values for each sample, the black area showing actual percentages and the lighter shaded area showing values x10. Whilst the filled curve is useful for providing an impression of changes over time, it can be misleading where samples do not come from a profile representing continuous deposition. The deposits

described in this report appear to be a mixture of short continuous deposition and sporadic depositional events.

Three series of three samples were submitted for pollen screening and subsequent pollen analysis (

Table 1). These samples were interpreted by archaeologists as representing primary and secondary fills in three composite cut depressions, in addition to natural sediments into which these features were cut (Figure 1).

Figure 1. Profile drawing of the defensive ditch (vollgrav) profile showing the location of pollen samples (circled dots, see

Table 1) and micromorphology samples (squares, see separate report from Richard Macphail and notes below). The pollen profiles, from left to right, are referred as profiles öst, mitt and väst in this report.

Depths given in the pollen diagrams are taken from this figure.

Table 1. Pollen sample series' from the defensive ditch.

Pollen profile öst Pollen profile mitt Pollen profile väst

14755 13886 (secondary fill) 13448

14754 13885 (primary fill) 13447

14753 13883 (underlying sediment) 13446

Table 2. Pollen taxa found in this investigation and their general environmental/cultural indications.

English name Deciduous woodland (Lövskog)

Coniferous woodland (Barrskog)

Meadowland /grassland (Ängsmark)

Cultivated /arable land (Åkermark)

Swedish (Norwegian) &

Scientific name

Alder X Al (Or) Alnus Birch X Björk Betula

Pine X Tall (Furu) Pinus Spruce X Gran Picea

Lime X Lind Tilia

Elm X Alm Ulmus

Oak X Ek (Eik) Quercus Hazel/Bog myrtle

type

X Hassel/Pors Corylus type

Heather X Ljung (Lyng) Calluna Goat Willow/

Willow

Sälg/vide (Vier) Salix

Juniper X En (Einer) Juniperus Grass X Gräs (Gras) Poaceae

Asters X Korgblommiga växter (rörf.), (Turf) Asteraceae undiff.

Cichoriaceae X Korgblommiga växter (Tungf.) (Tistel, Lövetann) Cichoriaceae Buttercups X Smörblommor (Soleie)

Ranunculus type

Rose family Rosväxter (Mure) Rosaceae undiff.

Mugwort X Gråbo (Burot) Artemisia vulgaris type

Chenopodioideae (goosefoots)

X Målla (Meldestokk) Chenopodiaceae

Pink family X X Nejlikväxter (Smelle, tjärnblom) Caryophyllaceae

Spurrey X Spärgel (Bendel) Spergula Nettles X Nässla (Nesle) Urtica Bedstraw Måra (Maure) Galium Hops/cannabis

type

X Humle/Hampa Cannabis type

Sorrels X Syror (Syre) Rumex Willowherb X Mjölkört (Geitrams) Epilobium Rattle X Skallra (Engkall) Rhinanthus

type

Tufted vetch type X Vicker (Vikke) Vicia cracca type Barley X Korn (Bygg-typ) Hordeum type Wheat/oats X Vete/Havre – typ (Hvete-typ)

Triticum

Rye X Råg (Rug) Secale Sedges X Starr (Storr) Cyperaceae Meadowsweet Älgört (Mjödurt) Filipendula Cow wheat X Kovall (Marimjelle)

Melampyrum

Cow parsley X Käx (Kjeks) Apiaceae

Spores Sporer

Lycopodium Lummer (Kråkefot) Lycopodium Ferns Ormbunkar (Telg)

Polypodiaceae

Lesser clubmoss Dvärglummer (Dvergjamne) Selaginella

Interpretation

Carbon particles

Carbon particles are present at low concentrations in the basal samples of profiles mitt and öst. The proportion increases up the profile and shows a dramatic increase in the upper sample of profile mitt (13886), suggesting an increase in human activity close to the ditch at the time of deposition.

Woodland vegetation

All three profiles display a similar picture of woodland vegetation. The proportions of coniferous woodland (pine) represented by the pollen are larger in the basal samples, decreasing and being replaced by alder and birch in the upper samples of each profile.

Profile väst (13448, 13447 and 13446) Figure 2

Profile väst lacks spruce pollen in its basal sample (13446), suggesting a date for its accumulation of earlier than ca. AD 1000. The upper samples contain only one grain of spruce pollen each, which could quite possibly be derived from long-distance transportation.

It is therefore also possible that these samples also date to before ca. AD 1000. On the basis of the pollen evidence, it is therefore possible that the entire feature of profile väst is older than the other profiles and older than AD 1000. On this basis it is also possible that sample 13446 predates the basal sediments represented in samples 14753 and 13883, which contain small amounts of spruce pollen. However, posthole construction/formation processes are complex, and these sediments could quite easily represent the use of older deposits to fill around a post dug into natural sediments. These results should therefore be interpreted with care and reference to a stratigraphic analysis of the deposits.

The proportion of pollen indicating cultivated land is low throughout this profile, with only a few grains from barley and rye present. Meadow/grassland plants, or indicators of

disturbance, are more frequent. The pollen assemblage suggests that meadowland was present at the site and that it became more prominent up the profile, although the reduction in pine in the upper sample is less significant than in the other profiles.

Profile mitt (13886, 13885 and 13883) Figure 3

The basal sample (13883) shows only a very weak indication of cultivated crops (one barley pollen grain), and thus a weak signal from arable lands. The micromorphology results also suggest that the sediment may not be entirely of natural origin, and that human activity may have been present on the site even if the farming activities only appear as a background in the pollen record. This could perhaps suggest construction of the ditch prior to the establishment of a settlement on the site. The indications of cultivated land in the rest of the profile are, however clearly stronger than in profile väst. The relative amount of pollen indicating a cultivated landscape increases with time, and both wheat and rye were most likely cultivated near to the site from sample 13885 onwards.

Pine trees dominate the initial arboreal signal, followed by alder and birch. Later layers show a decreasing proportion of coniferous woodland and increasing proportion of deciduous trees, especially birch. The proportion of carbon particles increases significantly up the profile, and may indicate extensive clearance burning in sample 13886. This activity is most likely after

the "short break in activities/waterlaid sedimentation" indicated in the soil micromorphology for the upper part of micromorphology sample 13901.

Profile öst (14755, 14754 and 14753) Figure 4

This profile demonstrates the highest proportion of cultivated/arable lands, with barley and wheat/oats present at high percentages. Barley and wheat/oats pollen is present in the basal sample (14753), indicating an anthropogenic landscape around this sediment. The proportion of cereal pollen increases considerably in the upper sample and cultivated land was most likely present at the site throughout the profile.

Soil micromorphology notes

Micromorphology samples 13900 and 13901 overlap the pollen analysis above and suggest that the cut for layer 14779 was made through the water table, and the latter sediments, containing pollen sample 13885, were deposited in standing water. The possible presence of tree buds in the 'natural' sediment (SA11) suggests that trees indicated in the pollen evidence (sample 13883) are either growing close to the ditch, or that there is periodic flooding leading to the deposition of these macrofossil traces against a background of more distant trees. The presence of woody fragments and leaves in finer layers above (14779) suggest that either the woody vegetation remains growing close-by on site, or that material from construction is finding its way into these sediments.

The layer 14780 appears also to have been deposited into standing water after a period of erosion (of layer 14779) which followed a period of stability and initial soil formation.

According to the micromorphology the depositional environment later becomes dryer, but no pollen samples were taken in these layers.

References

Beug, H.J. (1961) Leifaden der Pollenbestimmung fur Mitteleuropa und angrenzende Gebiete.

Lief. 1. 63 pp. Stuttgart.

Macphail (2016) Follobaneprosjektet: Follobanen FO4 Klypen-Øst soil micromorphology (including SEM/EDS). Report for NiKU, Norsk institutt for kulturminneforskning.

nstitute of Archaeology, University College London (UCL)

Moore, P.D., Webb, J.A. & Collinson, M.E. (1991) Pollen analysis. Oxford.

Appendices

Figure 2. Pollen percentage diagram from profile väst samples 13446, 13447 and 13448. Note that the samples do not represent continuous sedimentation within the profile, but three distinct depositional phases. (Sample depths have been read from photographs provided on submission of samples).

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 DEP

TH ( cm

) ₂₀

4060

O K LPA TI R AR KL >

m 25 ro ik et m

er 20

N AL S U

2040

E B TUL A

C PI A E

2040

NUS PI G FA

S URC UE Q

US S U IAM IL TUL CORY

LUS YP T E

SA

X LILL A C

UNA PO

C A AE E

AR TE IS M VU IA A LG IS R TY PE

ST A ER AC EAE UNDI . FF

CA N N AB IS T YP E

CA YO R PH LA YL EAE C

CHE NO PO AC DI AE E

CICHO AC RI EA E

EP O IL U BI T M YP E

AL G IUM YPE T

UM R EX C A O ET SA/

AC O ET SE A LL

SP ER U G T LA PE Y

URT A IC TYP E

ICIV A C AC R A C YPE T

SU M M ST A R Ö NG NI S INDI KE RA NDE ÄX V R TE

HO DE R UM YPE T

R T IC IT

UM SU

MMA OD D LA E VÄ ER XT

CY ERA P CE AE

AP C IA EA E

IL F E IP NDUL A

ME MP LA YR M U

RA UNCU N S TY LU E P

RO SA EAE C UNDI . FF

C LY OP OD M A IU N N TI O NUM

PO P LY D O IAC EA E T P Y E

PR V O R N

13886 13885 13883

FOLLOBANEN F04, KLYPEN ÖST VALLGRAV, POLLENPROFIL MITT Analys Jan-Erik Wallin Pollenlaboratoriet i Umeå AB jan. 2017

Figure 3. Pollen percentage diagram from profile mitt samples 13883, 13885 & 13886. Note that the samples do not represent continuous sedimentation within the profile, but three distinct depositional phases. (Sample depths have been read from photographs provided on submission of samples).

0 10 20 30 40 50 60 70 80 90 100 110 120 DE

TH P m (c

) 2040

KO LP RT A LA IK > R m 25 rom ik er et

20

N AL S U

204060

BE TUL A

C PI A E

2040

NUS PI FR AX U IN S

U Q ER U C S

LI TI

A M UL

S U CO

RY LU T S YP E

NI JU PER US YPE T

SA

LIX CA

UNA LL PO

AC

EAE AR

M TE IA IS VU LG R A T IS PE Y

AS RA TE CE E UNDI A . FF

CA PA M U N LA T YPE

CA N N AB TY IS PE

CA YOP R Y H AC LL EA E

CHE O N PO IA D EA C E

IC C O H AC RI EA E

AN PL G TA M O ED / IA MA JOR

U R EX M C A ET SA/ O AC O ET EL S LA

SP ER U G TY LA PE

CE TA N R U EA T YPE

R U C TI A T YPE

VIC C IA ACC R TY A E P

SU M M A ST RN Ö G IN S IN IK D RA E DE N ÄX V R TE

HO RDE M U YP T E

TRI

CUM M TI M SU

A OD DE LA VÄ XT ER

CY ERA P CE AE

AP C IA EA E

LI FI PE ND UL A

ME MP LA YR M U

RA U N CUL N S TY U PE

RO SA EA C E U DI N . FF

LY O C PO UM DI N A O N N TI UM

PO P LY D O IAC EA E T PE Y

PR V O NR

14755 14754 14753

FOLLOBANEN F04, KLYPEN ÖST VALLGRAV. POLLENPROFIL ÖST Analys Jan-Erik Wallin Pollenlaboratoriet i Umeå AB jan. 2017

Figure 4. Pollen percentage diagram from profile öst samples 14753, 14754 and 14755. Note that the samples do not represent continuous sedimentation within the profile, but three distinct depositional phases. (Sample depths have been read from photographs provided on submission of samples).

MAL

Miljöarkeologiska laboratoriet Umeå Universitet

901 87 UMEÅ 090-786 50 00 www.umu.se/envarchlab

mal@umu.se

Jan-Erik Wallin Pollenlaboratoriet i Umeå AB Sågställarvägen 2A 907 42 Umeå

070-66 15 101 pollenlaboratoriet@ume.se