Wood Studies -  Anne Crone

Introduction.

Selected samples of charcoal were analysed to examine wood usage on the site.

Some twenty-five samples were examined, two of which have been radiocarbon-dated (Table 1).  Three of these samples, S. Nos 16, 680 and 680/r25 are from the same context but show such variation that they are treated separately here.  The only criterion for selection was the presence of identifiable fragments, that is, fragments over 4 mm on at least one axis, and thus the samples are unevenly distributed throughout the stratigraphy of the site.

Heather (Calluna vulgaris) can be identified macroscopically by the twisted and pitted nature of its stems and it is therefore possible to know, at a glance, whether a sample is composed entirely of heather or whether other species are present.  Conifers can also be rapidly identified as to order (ie Coniferae) by simply looking at their transverse or cross-section but can only be identified as to genus or species if the fragments are large enough for other sections to be prepared.  Hence in Table 1, heather and conifers are quantified as proportions of the whole sample or their presence is noted.  Fragments identified as to genus and/or species are quantified in terms of numbers of identified fragments.
 

Results.

Heather is by far the dominant species in the assemblage; it is present in twenty-three samples and accounts for over 90% of the total in sixteen samples.

Coniferae are present in twelve samples.  While it has been possible in some cases to identify the conifer as to genus, the small size of the fragments has, in most cases, prevented identification as to species.  Thus larch (Larix sp.) is present in ten samples but in only one case has it been positively identified as European larch (Larix decidua).  Pine (Pinus sp.) has been found in three samples but only in one has it been identified as Scots pine (Pinus sylvestris).  A single fragment of spruce (Picea sp.) has been tentatively identified.

A handful of fragments of deciduous species are present in the assemblage.  One fragment each of ash (Fraxinus excelsior), rowan (cf. Sorbus aucuparia) and oak (Quercus sp.) have been identified.  Two samples contain several fragments each of willow (Salix sp.).
 

Discussion.

Heather forms a large proportion of the surface vegetation cover of the Shetland Isles (Berry & Johnston 1980) and would have found it way onto a domestic site rooted in peat turves used for fuel and as roofing and building material.

In the most recently published account of palynological work in Shetland (Bennett et al 1992) willow and rowan are present on the islands during the period under question, although in small quantities and this is reflected in the assemblage at Scalloway.  The evidence from the palynological record is inconclusive as to whether oak and ash grew on the island (op cit 261); these fragments may, therefore, have been driftwood.

All the Coniferae present in the assemblage must have been brought onto the island either arriving as driftwood or by direct importation.  They do not occur in such quantities as to suggest the latter although, in the absence of species identification and without the presence of marine molluscan boreholes (cf. Crone unpubl), it is impossible to state categorically the wood burnt was driftwood.  However, their scarcity and variety suggest the gleaning of the seashore.

Dickson has recently argued that finds of spruce and larch in the Northern Isles are unlikely to have come as driftwood from Europe for two reasons; firstly, spruce and larch are only found well inland of any north European coastline and secondly, the major currents flow northeast from North America into the Barents Sea and not westwards from Europe (Dickson 1992).  It therefore seems most likely that North America was the source of much of the driftwood with the exception, of course, of the worked fragment of European larch.  Pine could, of course, have found its way from the Scottish mainland to the Shetland Isles on those northeasterly currents.

As samples from only Phases 2, 3 and Block 12 (Phase ?) have been examined it is difficult to comment on wood usage over time. All that can be said is that a mixture of heather, driftwood and local woods were exploited in Phases 2 and 3.  Only heather is present in Block 12.
 

Radiocarbon dating

S. No. 707 has been requested for radiocarbon dating.  It contains 23 gr of pure Calluna charcoal.  Caution needs to be exercised when using Calluna for radiocarbon dating because of the possible presence of `old' Calluna in peat turves.  However, at Scalloway, two samples of Calluna have already been dated, the results of which accord well with the site stratigraphy, suggesting that the source was upper turves rather than deep-cut peat. I would therefore recommend this sample for dating.
 

References

Bennett K D, Boreham S, Sharp M J & Switsur VR  1992  `Holocene history of  environment, vegetation and human settlement on Catta Ness, Lunnasting,  Shetland', Journal of Ecology, 80, 241-273.

Berry R J & Johnston J L  1980  The Natural History of Shetland. London: Collins

Crone B A (unpubl)  `Tuquoy; the waterlogged wood'.

Dickson J H  1992  `North American driftwood, especially Picea (spruce), from  archaeological sites in the Hebrides and Northern Isles of Scotland'  Review  of Palaeobotany and Palynology, 73 (1992), 49-56.
 
 


Table 1 Catalogue of wood species present

Context

Block

Species

Quantity

Comments

620

6.2

Calluna vul.

100%

 

707

6.4

Calluna vul.

100%

 

673

6.6

Calluna vul.

50%

 

673

6.6

Coniferae

50%

Fragments too small to id

35

7.1

Calluna vul.

100%

 

539

7.2

Calluna vul

50%

 

539

7.2

Larix

present

Fragments too small to id

549

7.2

Larix sp.

2

 

578

7.2

Calluna vul.

100%

 

608

7.2

Calluna vul.

100%

 

732

7.2

Calluna vul.

5

Fragments too small to id but

   

Larix sp.

4

majority are coniferous

28

7.3

Calluna vul.

100%

 

616

7.3

Pinus syl.

5

 

616

7.3

Frax. ex.

1

 

616

7.3

Pom. cf Sorbus

1

 

616

7.3

Calluna vul.

present

C14 dated

616

7.3

Larix decidua

artefact

 

16

7.5

Larix sp.

3

1 frag 3.2 x 2.4 x 1.0 cm

16

7.5

Salix sp.

3

 

16

7.5

Calluna vul.

0

 

680/r25

7.5

Calluna vul.

99%

C14 dated

680/r25

7.5

Pinus sp

present

 

680

7.5

cf. Larix sp.

7

 

680

7.5

Salix sp.

2

1 frag 2.75 x 2.0 x 1.0 cm

680

7.5

cf. Picea

1

 

738

7.5

Calluna vul.

90%

 

738

7.5

Larix sp.

2

Majority of small frag are coniferous

749

7.5

Calluna vul.

50%

 

749

7.5

Larix sp.

2

Majority of small frag are coniferous

760

7.5

Larix sp.

3

Fragments too small to id

760

7.5

Calluna vul.

3

 

773

7.5

Calluna vul.

99%

 

773

7.5

Quercus sp.

1

 

773

7.5

Larix sp.

1

 

773

7.5

Pinus sp.

1

 

432

9.2

Calluna vul.

100%

 

59

12.3

Calluna vul.

100%

 

64

12.3

Calluna vul.

100%

 

76

12.4

Calluna vul.

100%

 

77

12.4

Calluna vul.

100%

 

78

12.4

Calluna vul.

100%

 

150

12.4

Calluna vul.

100%