Assessment of a Peat Core from Clogwynygarreg

ASSESSMENT OF A PEAT CORE FROM CLOGWYNYGARREG,

NORTH WALES

F.R.GRANT

ASSESSMENT OF A PEAT CORE FROM CLOGWYNYGARREG,

NORTH WALES

F.R.GRANT REPORT NO: 02/12

PRODUCED FOR ROYAL COMMISSION ON THE ANCIENT AND HISTORICAL MONUMENTS OF WALES

CONTENTS

1. NON TECHNICAL SUMMARY 1

2. INTRODUCTION 1

3. SITE SELECTION 1

4. LOCATION, GEOLOGY, TOPOGRAPHY AND VEGETATION 5

5. ARCHAEOLOGICAL AND METAL MINING BACKGROUND 7

6. PALAEOENVIRONMENTAL BACKGROUND 8

7. METHODS 9

8. RESULTS 11

9. INTERPRETATION AND DISCUSSION OF RESULTS 18

10 CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER WORK 24

11. ACKNOWLEDGEMENTS 24

12. REFERENCES 25

APPENDIX I: C14 data APPENDIX II: Geochemical Analysis Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

1. NON-TECHNICAL SUMMARY A 2m core was extracted from the mire adjacent to Clowynygarreg, North Wales, and subjected to radiocarbon dating, pollen, microscopic charcoal, and geochemical analysis. The results showed that the core contained a palaeoenvironmental record from the early Mesolithic (8525 +/- 27 C14 years BP), until present day. Pollen and microscopic charcoal evidence suggested that the area was predominantly wooded during the Mesolithic, with initially a mixed birch-pine-oak in the upland region and oak-elm-hazel cover on the deeper soils. Throughout the Mesolithic the area remained generally wooded, but with variations in the composition, and some indications of disturbance by burning. An alder carr began to develop on the valley bottom during the Mesolithic. The Neolithic is marked by the disappearance of elm from the record, and an increase in open, grassland species, and slight evidence for cultivation in the form of a cereal-type pollen grain. Open areas increase into the Bronze Age with increased evidence for pastoralism, burning activity and cultivation. However, heath conditions do not seem to form here until the later Bronze Age at the earliest, and no direct evidence for prehistoric mining could be identified from this assessment. Evidence for increased lead deposition during the Roman period is tentatively suggested by the geochemical record, but this appears to be of low-level or regional origin. Increased industrial activity in the area during the Medieval period is suggested by increased levels of heavy metal deposition. Similarly, the pattern of lead deposition for the post-Medieval period follows that for other industrialised areas, and increases in copper demonstrate the known period of exploitation of the copper resources at Drws y Coed mine.

2. INTRODUCTION

In January 2012 the author was invited by the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW) to undertake a palaeoenvironmental and geochemical study of a peat core from an area of Snowdonia, North Wales, formerly affected by metal mining. The resulting information would contribute to both the RCAHMW Uplands Initiative, and the Metal Links Project.

A programme of desktop work was initiated during January 2012, with follow-up field visits to identify a suitable site. Coring took place in May 2012. The results of the subsequent palaeoenvironmental, geochemical and radiocarbon analysis form the basis of this report.

3. SITE SELECTION

Metal Mining in Snowdonia The exploitation of metalliferous ores has a long heritage in North Wales in general. Relatively large-scale Bronze Age mining of the copper deposits has been identified at Mynydd Parys and Pant y Gaseg in Anglesey, the Great Orme near Llandudno, Corbet Dovey and Pant Eidel mines in southern Gwynedd, and Trecastell in Aberconwy (Gwyn 1998). Further afield, the copper mines in Cwmystwyth in Ceredigion, and Nantyreira in Powys, are also known to have prehistoric origins (Timberlake 2003; Timberlake 2009). Whether less intensive exploitation of smaller deposits of ore in the uplands of Snowdonia formed part of a mixed agricultural and industrial economy during this period is not known, but is undoubtedly possible. Certainly the intensification of settlement and exploitation of the

1 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

upland area during the Bronze Age is well attested to by the wealth of archaeological monuments dating to this period.

Roman exploitation of the copper ores at Mynydd Parys is also suggested by the finds of copper cakes bearing Latin inscriptions. The locations of Roman forts close to the sources of known lead and copper ores, such as that near Sygun at Beddgelert, and in the Gwydir area of Snowdonia, imply further exploitation during this period, (Kelly 1976). Evidence for Medieval exploitation is based mainly upon historical references rather than archaeological evidence. However, during the post-Medieval and Industrial periods exploitation increased dramatically. The Gwynedd Metal Mines Survey (Gwyn 1998) identified over 300 sites exploiting lead, and over 160 exploiting copper during this period in Gwynedd as a whole.

Owing to the abundance of known metal mining sites within the study area, the broad remit of the original specification was therefore narrowed somewhat, in order to facilitate identifying a suitable site for analysis. To maximize the potential of the deposits to retain a record of mining activity, only those within a 5km radius of known former mining sites were considered. Other considerations included the type of mire, other archaeological sites in the immediate area, the proximity and nature of previous palaeoenvironmental studies, accessibility, and any special status to either the mire or the archaeology which could prove problematical for sampling.

The primary sources of information for the desk-top study were the Gwynedd Metal Mines Survey (Gwyn 1998), Gwynedd Archaeological Trust’s Historic Environment Record (HER), COFLEIN, and the Welsh Lowland Peatland Survey (Ratcliffe and Hattey 1982). Cartographic material and aerial photography were also utilised. Consultation with the Snowdonia National Park’s archaeologist, and the RCAHMW provided an additional list of potential mire sites.

Figure 1 details those sites considered for assessment.

2 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

SITE NAME GRID MIRE CLOSEST METAL OTHER REF TYPE & MINING EVIDENCE ARCHAEOLOGICAL DEPTH (WITHIN 5KM) EVIDENCE Cwm Ciprwth SH5223 Blanket and C19th copper mine PRN Prehistoric, medieval and 4803 basin: 20515 post-medieval settlement c.1.5m 250m adjacent to mire NW of mine workings Coed Mawr – SH7830 Lake & fen: C17th-C19th lead mine, ?pre AD1697 mining activity Llyn Pencraig 5840 2m+ PRN 21678 Roman fort of Bryn y adjacent to Gefeiliau. mine Clogwynygarreg SH560539 Basin: 2m+ Drws y Coed C19th copper Prehistoric settlement and mine. Historical evidence funerary/ritual evidence. for possible medieval Medieval settlement. Post exploitation. PRN 20535 medieval settlement (abandoned) Mire West of SH538 535 Valley: 2m+ Drws y Coed C19th copper Prehistoric settlement and Drws y Coed mine. Historical evidence funerary/ritual evidence. (Mire 2) for possible medieval Medieval settlement. Post exploitation. PRN 20535 medieval settlement (abandoned) Mire on valley SH547 536 Blanket: Drws y Coed C19th copper Prehistoric settlement and side above Drws c0.75m mine. Historical evidence funerary/ritual evidence. y Coed mine for possible medieval Post medieval settlement (Mire 3) exploitation. PRN 20535 (abandoned) Muriau’r Dre SH65 54 Blanket: None – Cu and Fe Late prehistoric settlement. <1m bog on smelting slags recovered Medieval settlement site from area. Coed Cilcennus Fen: 0.75m Small C18th-C19th lead Roman palstave find site. on site mine. PRN 21116 Clogwyn Coch SH60292 Blanket: Clogwyn Coch C19th Medieval settlement 55900 0.70m max copper mine PRN 20798 Basin: 0.90m max Penygyrd SH66590 Blanket: None Bronze Age funerary and 55035 0.75m (Fyfe ritual forthcoming) Gwaun Gynfi SH6064 Not tested Ceunant Mine PRN 20807 Very limited copper and arsenic mining Llyn Arenig Fach SH8241 Not tested PRN 21852 Moel Bronze Age funerary and Llechowgryn Manganese ritual mine Mochowgryn, SH8040 Not tested PRN 21852 Moel Bronze Age funerary and Arenig Fach Llechowgryn Manganese ritual mine Llyn SH6556 Blanket: PRN 20789 Britannia Cu Cwmffynnon 1m+ Mine Llyn Gwythwrch SH570579 Basin: 1m+ PRN21587 Llanberis Cu Prehistoric funerary and mine settlement Llyn Ffynnon-y- SH5955 Blanket: Clogwyn Coch C19th gwas <1m copper mine PRN 20798 Basin: c.1m Figure 1: Potential Assessment Sites

3 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

A range of sites were assessed, all of which fulfilled some of the criteria required. After consultation with RCAHMW it was decided to take a sample from the basin mire at Clogwynygarreg. The reasons for this decision are discussed below.

The mire is located close to an area of extensive 18th and 19th-century copper mining and processing at Drws y Coed, and should potentially have been in receipt of airborne pollutants related to the exploitation there. Historical records refer to mining there in the Medieval period, and potential prehistoric mining activity has also been suggested (Gwyn 1998, 55). Archaeological field survey has identified probable Bronze Age activity around the mire, with Medieval and post-Medieval settlement also recorded (Oxford Archaeology North 2006). Previous palaeoenvironmental analyses (Ince 1996) have identified the suitability of the deposits as an important archive of palaeoenvironmental information. The work would complement the earlier analysis by Ince, adding further to the record of vegetation development, and exploring the human activity in the area as implied by the archaeological record. The impact of the post-Medieval metal mining upon the landscape may be recorded in the deposits, and any potential earlier phases identified. It would test the usefulness of the deposits to retain a record of later changes, particularly in light of the landscape alteration of the basin (see below). Additionally, the study would form a basis for any potential future work as part of the Metal Links project which may focus upon the Drws y Coed area.

Other mires in the area include the valley mire (Mire 2) west of Drws y Coed, and a small area of blanket and spring-fed soligenous mire (Mire 3) close to the prehistoric settlement above the mine workings (SAM number CN209). The valley mire, although containing deep deposits of organic material, was considered to be more likely to be negatively affected by flooding, and potential in-washing of older material, for the purposes of this study. The deposits around the prehistoric settlement were also discounted at this stage owing to their shallow nature which may limit the time span of the palaeoenvironmental record.

4 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

4. LOCATION, GEOLOGY, TOPOGRAPHY AND VEGETATION

The site lies on the western edge of the Snowdonia uplands, in Gwynedd, North Wales, (centred on NGR 2561 3539). The village of Rhyd Du lies c.1.5km to the south-east, and Nantlle c.5km to the west.

Fig 2: Location of Clogwynygarreg Contains Ordnance Survey data @ Crown copyright and database right 2011 (www.ordnancesurvey.co.uk/oswebsite/opendata)

5 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Mynydd Mawr 698m

Llyn Cwellyn

Mire at Clogwynygarreg

Afon Drws y Coed

Mire 3 Drws-y-Coed Clogwynygarreg 336m Mire 2 Llyn–y-forwyn

Main area of 18th-19th century

mining activity Rhyd-Ddu Areas of mire B4418

Approx. location of sampling site 1km

Fig 3: Sites mentioned in the text

The underlying geology is of mudstones and shales of Ordovician age belonging to the Arenig-Llandeilo Series. To the south and north-west are outcrops of slates and grits of Upper Cambrian age, and to the east there are Ordovician slates. Acidic rhyolites and rhyolitic tuffs outcrop further east and north-east towards the Snowdon massif (British Geological Survey 1994).

The mire at Clogwynygarreg has developed within a former lake basin, occupying one of a series of glacial meltwater channels in the area. It stands just to the north of the small lake Lly-y-Dywarchen, which forms the watershed between the Nantlle Valley to the west and Llyn-y-Gader and the Gwyrfai valley to the south-east and east. Clogwynygarreg is actually the name of the rock crag, rising to 336m, lying immediately to the west of the mire, which partially separates it from the more open Nantlle Valley further to the west. The mire curves around the eastern and northern sides of this crag. Earlier palaeoenvironmental analysis by Ince (1996) demonstrated organic deposits within the mire basin to a depth of 7.4m. These provided key information on the vegetational and climatic changes within the area during the Late- Glacial and early Holocene. The results of this work led to the mire being designated a Site of Special Scientific Interest (S.S.S.I.).

The mire surface is dominated by grasses, mainly Agrostis tenuis (bent), Nardus stricta (matt grass), and Festuca spp (fescues). Agrostis-Festuca grasslands occupy the surrounding slopes. Also noted were Erica tetralix (cross-leaved heath), Eriophorum angustifolium (cottongrass), Sphagnum spp. (bog mosses), Narthecium ossifragum (bog asphodel), Carex spp. (sedges), and Potentilla erecta (tormentil). The margins of the mire are flanked by Juncus spp. (rushes), and raised drier areas support Calluna vulgaris, (heather), Vaccinium myrtillis (bilberry) and occasional Sorbus aucuparia (rowan). Alnus glutinosa (alder) occupy wetter areas in the northern part of the mire.

6 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

5. ARCHAEOLOGICAL AND METAL MINING BACKGROUND

The area is included in the RCAHMW inventories (1960, 1964), and was later surveyed under the RCAHMW Uplands Initiative in 2006 (Oxford Archaeology North 2006). The National Monuments Record of Wales identifies 76 sites within a c.1km radius of the mire, with many of these relating to the agricultural and industrial exploitation of the area during the post-Medieval and Industrial periods.

The area is relatively rich in evidence for prehistoric settlement and funerary activity. Bronze Age cairns top many of the summits in the area (e.g. NPRN 302602), and further small cairns and possible cairnfields have also been identified. Adjacent to the mire is a possible burnt mound (NPRN 287114), a characteristic indicator of Bronze Age activity. Prehistoric field systems and associated roundhouses, such as those on the western flanks of Mynydd Mawr (NPRN 24298, 287090, 287092, 287079, 287078, 287297, 287290, 287298), demonstrate relatively extensive settlement activity, and are of sufficient importance to merit Scheduled Ancient Monument status (SAM number CN179). Smaller settlements also exist such as Drws y Coed Prehistoric Settlement (NPRN 93678, SAM number CN209), and individual roundhouses.

Longhouse structures and platform houses are found throughout the general area, and are believed to relate to Medieval settlement. These include the longhouse at Bwlchgylfin (NPRN 287192) and those overlooking Llyn-y-Gader (NPRN 287199 and 287203).

Sheep farming has left many structural remains upon the area in the form of sheepfolds (e.g. NPRN 287110, 287134, 287135), and shelters (e.g. NPRN 287133, 287148), and the former farmhouses and associated out-buildings (e.g. NPRN 287138, 287160). On and around the slopes of Clogwynygarreg and around Llyn y Dywarchen are numerous such buildings (e.g. NPRN 287163), with associated field systems, and evidence of peat cutting from the mire (e.g. NPRN 287132, 287136, 287141).

The area has a rich history of copper working. The mine workings at Drws y Coed, extend to less than 0.5km to the west of the mire, and are described by Gwyn (1998, 55) as “one of the outstanding mining landscapes of Gwynedd”. Prehistoric workings have not been identified, although they have been suggested by several authors. Edward I is reputed to have visited the mines in 1284, and the site was extensively developed by 1760. Operations continued into the 1920s. (idem). Further details of the structural remains of the copper workings of the area are contained within the report by Oxford Archaeology North (2006).

As part of the copper workings at Drws y Coed, a dam was constructed in the mid 19th- century at the northern end of the mire to restrict the flow of water, flood the area and create a reservoir. The resulting Llyn Bwlch-y-moch, stood until sometime after 1960, when it was breached and the lake drained, returning the mire as we see it today.

7 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

6. PALAEOENVIRONMENTAL BACKGROUND

Work by Ince (1996) identified over 8m of organic and non-organic deposits in the basin at Clogwynygarreg. The earliest pollen identified was at 7.92m, but concentrations were very low. Detailed analysis took place between 6.30m and 7.45m, and provided evidence of the late-glacial and earliest Holocene vegetation of the area. Herbaceous taxa dominated in the earliest phases investigated, with Rumex spp. being particularly dominant. Juniperus subsequently expanded into these pioneer grasslands, but then diminished in the latter half of the late-glacial Interstadial, with a revival of the Rumex-dominated grasslands. A brief resurgence of Juniperus is followed by indicators of disturbed ground conditions and colder conditions, related to the Loch Lomond Stadial. A marked rise in Juniperus followed by the establishment of Betula woodland indicates the onset of an improvement in climatic conditions in the early Holocene.

Four radiocarbon dates were obtained from the deposits analysed by Ince. Unfortunately anomalies within the sequence suggest some contamination by older/younger material within the basal samples, and within that related to the Loch Lomond Stadial/Holocene transition. These are thought to be related to the unstable conditions related to periglacial processes, causing reworking and erosion of material.

Snowdonia in general has one of the most thoroughly investigated pollen records in Britain (see Rhind and Jones 2003). Much of this interest is due to the presence of numerous glacially formed lakes which can provide information on the vegetation and landscape development from the Late-glacial period c.12,000 years ago. One such site, closest to Clogwynygarreg, is Llyn Dwythwch, (c.4km north-east). Here, tundra-like conditions in which Betula nana flourished, existed during the Late-glacial. Whilst Juniperus subsequently expanded, tree birches failed to establish during this period, owing to the elevation of the site. Again the Loch Lomond Stadial is reflected in the evidence for unstable ground conditions and an increase in montane herbs, mosses and ferns (Seddon 1962).

Investigations at sites such as Llyn Cororion (Watkins 1990), Nant Ffrancon (Seddon 1962), Llyn Llydaw (Ince 1983), Cwm Idwal (Godwin 1955; Tipping 1993) have provided information on the subsequent Holocene development of the region, identifying the transitions from juniper scrub to birch forest, then mixed hazel and oak woodlands. Human impacts are identified throughout Snowdonia, from the earliest small-scale woodland disturbances of the Mesolithic (e.g. Chambers and Price 1985). A generalised picture shows over time that as the upland woodland diminished through clearance, fire and grazing, open grassland areas increased, and areas of blanket bog began to develop. In some lowland areas woodland remained relatively extensive until the Medieval period. However, at Dinas Emrys, c.6.5km south-east of Clogwynygarreg, analysis of the deposits depicts a relatively open grassland environment by c.AD500, in which much of the forest in the area had been cleared (Seddon 1960).

8 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

7. METHODS

Sample Extraction Sample extraction at the selected site took place on 13.05.12. Probing was used to identify peat of a maximum depth, and areas where peat cutting was evident were avoided. A site towards the northern end of the mire was selected, to maximise inputs of airborne pollutants from the mining areas to the west. The core was extracted using a Russian corer. The cores were immediately wrapped in plastic film, labelled, and covered in black polythene before being transported to cold storage in the laboratory. A photographic record of the area and the process involved was maintained.

The samples were cleaned and a visual stratigraphic description was compiled which allowed description of the botanical composition of the peat, as well as an estimation of the degree of humification.

Pollen Preparation and Analysis Eight initial sub-samples were extracted from the core. This number of sub-samples maximised the efficiency of the pollen preparation (in which 8 samples can be processed at a time), and allowed a useful data set to be achieved which could be utilised for any possible future research. After cleaning of the profile surface, 1 cm sub-sampling was carried out, Owing to the possibly disturbed nature of the upper 0.5m of core, (see below), sub-sampling was carried out below this zone only. Sub-samples were therefore taken from the following horizons: 0.64-65m, 0.90-91m, 1.10-1.11m, 1.30-1.31m, 1.50-1.51m, 1.70-1.71m, 1.90- 1.91m and 2.10-2.11m. The samples were subjected to standard potassium hydroxide digestion and acetolysis as described in Moore et al (1991). After dehydration in ethanol, then tetra-butyl alcohol, the samples were mounted in silicone oil.

Counting and identification was carried out using an Zeiss Axiolab at x400 magnification, and with the aid of the reference collection type slides of the Palaeoecological Research Unit at the University of Manchester, online pollen image databases, and the pollen and spore key in Moore et al. (1991). Linear traverses of the slide were carried out at 1mm intervals from one edge to the other, and in one direction only.

A minimum total pollen sum of 400 land pollen grains plus spores and aquatics was attained from each sample. This count value would allow meaningful results to be incorporated within any possible further research without additional counting being required. The nomenclature used is principally that of Bennett (1984), with additional notes from Moore et al. (1991).

Microscopic charcoal particles were counted as they were encountered during the general pollen count. These were then represented as a percentage of the TLP sum.

Geochemistry The multi-element geochemistry of the core was carried out by Dr Henry Lamb at the Institute of Geography and Earth Sciences in the University of Aberystwyth using the XRF scanner. Scan resolution was set at 800µm intervals, with a dwell time of 200ms per increment. X-radiography and digital RGB optical imagery provided information on density and colour of the material scanned. The core was scanned in two parts, with an overlap between them, thus forming two records; 0.1m–1.6m and 1.1m–2.1m. Results were supplied in Excell spreadsheet format, and plotted graphically using dedicated software.

9 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Radiocarbon Dating Two samples for radiocarbon dating were extracted from the profile, as specified in the brief. A peat sample was extracted from 0.52m and a wood (twig) sample from 2.06m. The comparison of the two dates should allow a broad estimation of sediment deposition rates (peat accumulation) to be attained, allowing correlation with other investigated sites and providing a guide time-scale for any changes noted in the pollen data.

Samples for radiocarbon dating were first air-dried then wrapped in labelled aluminium foil packages before being bagged in polythene sample bags. Owing to the small weight of the samples they were submitted for Accelerator Mass Spectrometry (AMS) at SUERC, University of Glasgow, Scotland. Calibration of the dates was determined using the University of Oxford Radiocarbon Accelerator Unit calibration programme (OxCal3). A crude sediment deposition curve was created for the profile using the conventional radiocarbon date. A trend line was added to allow inter and extrapolation of the data in order to estimate a date for other levels of the core (Dark 2000, 12). It should be noted that the deposition curve is based on the central age estimate and should not be taken as a precise date. In addition problems in attempting to create a constant deposition curve based on only two dates are discussed below.

Methodological Considerations Pollen analysis has a long pedigree in the history of palaeoenvironmental studies, and has proved an invaluable tool provided certain considerations are taken into account. These include methods of dispersion and survival of pollen grains, a recognition of sampling distortion and the concerns of representativity of a single sample from a site, issues of contamination, and statistical problems both in the manipulation and the interpretation of the resulting data. Despite the elements of uncertainty brought in by all of the above considerations, in general terms the value and versatility of pollen analysis as a palaeoenvironmental tool is undisputed. The remarkable degree of consistency from the many studies undertaken underlines the value of pollen analysis.

Similar considerations need to be applied when discussing the results of radiocarbon dating and peat accumulation rates. Radiocarbon dating provides only an age estimate rather than a true date for an object or an event. As such a direct chronological relationship between events suggested in the pollen record and historical events should only be implied, particularly when only one or two radiocarbon dates are acquired, and when dates are achieved by interpolation of individual dates which implies a constant deposition rate for the sediment. For a truly meaningful sediment deposition rate to be ascertained several radiocarbon dates should be acquired in order to mitigate for changes in the accumulation rate over time.

10 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

8. RESULTS

A 2m core was extracted from NGR255913 3532977. At this depth a dense layer of wood was encountered which could not be cored through manually with the Russian corer. Probing revealed that this layer extended into much of the surrounding area. However, it was considered that 2m of material should provide sufficient information pertinent to the project requirements.

Profile Stratigraphy The lower part of the core from 0.78m consisted of well humified moss peat with occasional fragments and thin layers of wood. Above this the stratigraphy was more complex, with bands of mineral–rich material alternating with organic material. A distinctly organic-rich mineral soil deposit was noted at 0.35-0.48m.

Depth m. Description 0-0.35 Dark blackish-brown. Humified Sphagnum peat Occasional monocot leaves, and rootlets. 0.35-0.48 Dark greyish-black. Organic rich soil 0.48-0.50 Olive Silty-clay 0.50-0.54 Dark brown Humified Sphagnum peat 0.54-0.56 Olive Silty-clay 0.56-0.78 Mid brown Detritus mud Occasional monocot leaves 0.78-2.10 Dark blackish brown Well-humified Sphagnum peat Occasional fragments of wood, increasing with depth Fig 4: Profile Stratigraphy

Radiocarbon Dating The radiocarbon dating information is presented in the table below.

Sample Laboratory Radiocarbon Calibrated date Historical Number Age BP 95.4% probability Period 0.52m SUERC 2146+-24 95 -296calBC Iron Age 41892 (GU 28003) 2.06m SUERC 8525+-27 7592 – 7537calBC Early 41893 (GU Mesolithic 28004)

Fig 5: Radiocarbon dating information

11 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

The application of a trendline in order to interpolate dates for such a long timespan using only two radiocarbon dates is problematical and provides only a crude tool for age estimation of the sediment throughout the core. However, with these provisos in mind, such a technique may still provide a useful tool to broadly estimate the chronology of changes within the pollen diagram.

9000

8000

7000

e 6000

o b

r 5000

o i

a R

4000

al al

n o

i nt

e 3000

n o

C 2000

1000

0 0 0.5 1 1.5 2 2.5 Depth (m)

Fig 6: Estimation of peat accumulation

Pollen Analysis Pollen was present throughout the core, and preservation and concentration was generally good. The exception to this was the sample from 2.10m in which concentrations were lower. In addition the sample was dominated by the spores of Osmunda regalis (royal fern). Elsewhere, a full count of 400 TLP (total land pollen) was achieved for each sample.

General trends in vegetation change may be implied from the pollen diagram. However, because of the large timescale represented between the samples, it is not considered appropriate to zone the diagram, and each sample is considered individually.

8 2

52 14

5 6

± ±

2 2

7 6

Depth (cm)

2 2 1 1 1 1 1 1 1 1 1 1

9 8 7 6 5 4 3 2 1

1 0 9 8 7 6 5 4 3 2 1 0

0 0 0 0 0 0 0 0 0

0 0 0 0 0 0 0 0 0 0 0 0 0

0 0

igu

log

rr 0

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and

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Diag

0 0

)

0 0

Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

2.10-2.11m c.8700 14C yrs BP (extrapolated) - Mesolithic (Earlier) This sample is dominated by the pollen of shrub and arboreal species, implying a predominantly wooded landscape with few open areas. Betula (birch) dominates the arboreal taxa at c.29% TLP, although Pinus is also an important component forming c.14%. Quercus (oak) and Ulmus (elm) each constitute c.7%, with Alnus (alder) and Sorbus (rowan) also present. Corylus (hazel) is important, forming c.31% TLP, with lower values of less than 5% of Salix (willow).

Values for Poaceae (grass) and Cyperaceae (sedges) are low, constituting less than 5% TLP together. Herbs such as Filipendula (meadowsweet) and Achillea-type (yarrow) are represented by single grains only.

Spores of ferns, in particular Osmunda regalis dominate this sample, although Polypodiaceae and Pteridium aquilinum (bracken) are also represented.

1.90m – 1.91m c.7850 14C yrs BP (interpolated) - Mesolithic Values for arboreal species decline in this sample to less than 40% TLP, as Cyperaceae increases, suggesting an increase in damp, open areas. Betula dominates the arboreal spectrum, accompanied by Quercus. Pinus and Ulmus have decreased in importance, although Corylus has increased to almost 40% TLP. Salix, however, has declined to less than 1% and remains low throughout the profile.

The increase in Cyperaceae is accompanied by the appearance of other herbaceous species such as Ranunculus (buttercups), Filipendula, Solidago-vigaurea-type (e.g. golden rod, daisy etc.), Achillea and Succisia pratensis (devil’s bit scabious).

Equisetum (horsetails) are recorded, and spores of Sphagnum spp. demonstrate a small peak.

1.70m – 1.71m c.7000 14C yrs BP (interpolated) - Mesolithic Arboreal values increase to c.70% TLP in this sample. This is predominantly owing to a substantial increase in Alnus to c.25% as an alder carr develops on the site. Betula, however remains important, and Pinus has also increased. Corylus has declined to c.20%.

A small peak in dwarf shrubs, notably Calluna vulgaris (heather) is recorded in this sample, accompanied by a peak in microscopic charcoal deposition. Values for herbaceous species have declined again to less than 10% TLP, and include Ranunculaceae, Succisia, Filipendula and a single grain of Chamaenerion angustifolium (willowherb).

1.50m - 1.51m c.6200 14C yrs BP (interpolated) - Mesolithic (later) Arboreal pollen values dominate this sample, owing to the swamping of the sample by Alnus pollen. However, Quercus pollen has also increased to almost 20% TLP, accompanied by a slight rise in Ulmus. Pinus, Betula and Corylus have all decreased significantly.

14 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Values for herbaceous species are correspondingly low. Dwarf shrubs are not represented, and values remain low throughout the remainder of the samples analysed.

1.30m-1.31m c.5400 14C yrs BP (interpolated) – Mesolithic–Neolithic Transition A similar picture is reflected in this sample, as the alder carr remains the dominant feature of the local environment. However, Corylus has now expanded at the expense of other tree species, and Ulmus and Pinus are represented by single grains only.

Values for herbaceous species remain very low, and a slight peak for aquatic species such as Myriophyllum is recorded.

1.10m-1.11m c.4500 14C yrs BP (interpolated) - Neolithic Arboreal pollen values remain high at c.83% TLP, with Betula demonstrating a recovery, and Alnus correspondingly declining. Values for other tree species such as Quercus and Ulmus remain low, although Tilia cordata (small-leaved lime) was recorded, as well as Sorbus. Corylus has suffered a decline to c.6%.

Values for open area species such as Poaceae and Cyperaceae have increased somewhat, accompanied by other herbs such as Plantago lanceolata (ribwort plantain), Filipendula, and Ranunculaceae. Cereal-type pollen is recorded for the first time, albeit by a single grain only.

0.90m-0.91m c.3700 14C yrs BP (interpolated) – Later Neolithic-Early Bronze Age The relatively high values for Alnus continue to reflect the local presence of an alder carr at the site. Generally however, values for arboreal species are beginning to fall. Betula remains relatively significant, although it has declined to less than 15% TLP, and Quercus, Ulmus and Corylus have both increased very slightly.

Species indicative of open areas continue to increase, with Poaceae and Cyperaceae forming together almost 20%, and again a single cereal-type grain is recorded. Floristic diversity however, remains low, although a single grain of Chamaenerion angustifolium is noted.

A peak in the spores of Pteropsida (ferns) accompanies a rise in microscopic charcoal deposition.

0.64m-0.65m c.2600 14C yrs BP (interpolated) – Later Bronze Age Arboreal pollen values continue to fall, representing c.60% TLP in this sample. All tree species including Alnus are declining. However, variety has increased with both Fraxinus (ash) and Ilex (holly) being recorded, albeit by single grains only. Corylus demonstrates a slight increase to almost 15%.

Herbaceous species have increased to c.25% TLP, indicating an expansion of open areas. Increases in both Poaceae and Cyperaceae are recorded, as well as a range of herbs such as

15 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Rumex (docks and sorrels), Plantago lanceolata, Ranunculaceae, Filipendula and Potentilla (tormentil).

Values for microscopic charcoal deposition remain relatively high.

Geochemical Analysis The full results of the geochemical analysis are contained within the appendix. Note should be taken that the base of the core extracted and represented in the diagrams, is not the base of the peat deposit. Additionally end-of-core anomalies occur in the data based upon the 0.5m extracted lengths of core. Peat is not the ideal medium for XRF analysis owing to the high water and organic contents, which are expressed as inc (incoherent scatter). Presenting the results as ratios against the incoherent scatter can assist in normalising the results to correct for the variation in water and organic content. However, in this case, little meaningful variation was noted in the normalised results, and the discussion is based upon the original data. Some discrepancy was noted in the overlap regions of the analysis. Further work is required on the geochemical results in order to explain this difference.

Based upon the radiocarbon dates, for the purposes of this project those areas of most interest within the geochemistry profiles are from c.4000BP (c.1m-top). The results for key elements for this part of the core are shown in Figure 7. Between 0.40m (c.1600 BP interpolated) and 0.1m the elemental profiles remain relatively constant (disregarding the end of core anomalies either side of 0.60m), although a very slight increase in values for Pb is noted around 0.41-0.42m (c.1750BP interpolated). Between 0.40m and 0.27m values for lead (Pb) begin to increase slightly, accompanied by increases in silicon (Si), sulphur (S) and bromine (Br).

From c.0.27m, (C.1200 BP interpolated) values for the selected elements begin to rise more dramatically. Copper (Cu) is identified only sporadically throughout the core and at very low levels. Whilst individual spikes in the values for Cu are probably not especially relevant, there is a consistent increase in the frequency of these spikes within the upper 0.20m of the core. There is a particular rise in values for Pb, Si, Ca and Fe around 0.20m (c.800BP interpolated). Values for lead deposition peak around 0.13m before declining to the surface. This decline is replicated by Si, S, Ca, Br and Fe. Titanium (Ti) however, forms a peak in this upper portion of the core.

16 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

8 II I

IIill 1 1 , '''" I '" i ,j ,,

Depth 0_1 0_16 0_22 0_27 0_33 0_39 0_4-5 0_5 0_56 0_62 0_68 0_73 0_79 0_85 0_91 0_96 (m)

17 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

9. INTERPRETATION AND DISCUSSION OF RESULTS

Sampling Interval and Chronology The restrictions of the assessment process mean that the sampling interval is wide. From the inferred chronology this may represent between eight hundred and over one thousand years. In addition this chronology itself is still rather crude, based as it is upon interpolated dates from only two radiocarbon dates. These factors have to be taken into account when attempting to apply a calendar date to events noted in the assessment, and as such dates may only be broadly inferred from this data.

Stratigraphic Change in Upper c.0.5m The upper c.0.5m of the core demonstrates a layering of organic-rich, and more mineral-rich material. The reasons for these changes are undoubtedly complex and relate to changes in land-use and human activity, as well as possible natural change.

From historical records it is known that the basin was flooded in the mid-nineteenth century to provide a reservoir to power the copper mining and processing industries at Drws y Coed. The basin remained flooded until sometime after 1960, when the dam was breached and the area returned to bog. It is also known that peat cutting has taken place in various areas across the mire. Increased clearance of the slopes around the mire would also have led to increased soil run-off.

These events will undoubtedly have had an influence on the physical and chemical attributes of the mire. The presence of a lake would have lead to the accumulation of lacustrine deposits, as well as affecting the hydrology of the underlying deposits. In addition any turbulence in the waters may have led to removal and reworking of previously deposited material. Increased run-off from surrounding slopes may introduce older, mineral-rich material to the mire, distorting the chronology.

Within the limits of the assessment it was therefore decided not to sub-sample within the upper 0.5m. However, the assessment has shown that it is only through further analysis of material from this part of the core, and the application of additional radiocarbon dating, that these potential issues can be tested. It is indeed possible that much of this upper zone does in fact contain useful information, pertinent to the project aims. The dates acquired so far, although limited in number, do suggest that evidence for vegetation change prior to 2146+- 24BP is successfully retained within the deposit. In addition the relevance of the geochemical evidence in this upper portion of the core is compelling when compared with analyses from elsewhere.

Geochemistry, Mire Type and Metal Mining Metal mining and ore processing may release quantities of heavy metals into the atmosphere which are then deposited within the local or regional environment. Metal ores such as chalcopyrite (copper) and galena (lead) are commonly found in association, and may be exploited simultaneously or selectively, resulting in multiple pollutants being released. In addition, quantities of microscopic charcoal deposition may be expected to increase, resulting from the burning of wood for fire-setting and smelting. Vegetation changes such as clearance, which may be selective in nature as specific wood types are selected for fuel, (e.g. see Heiss and Oegg 2008) and increased disturbance, may be identified from the pollen record.

18 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Investigations at early copper working sites such as Copa Hill have identified high levels of copper within the surrounding peat deposits, associated with the known periods of activity there (Mighall et al. 2002). The sources of lead contamination are varied. It may have lithogenic (soil dust) origins, but its presence is commonly used as a marker in geochemical studies of peat and other materials such as ice cores to identify atmospheric pollution from, for example, Roman period lead mining and smelting (Hong et al. 1994; Le Roux et al.2004; Martinez Cortizas et al. 2002), coal burning, and the changes in the lead content of gasoline (Le Roux et al. 2005; Novak et al. 2008; Weiss et al. 1999).

Ombrotrophic (rain-fed) peat is widely recognised as containing the most reliable archive of heavy metal deposition (Shotyk 1996). This is owing to the fact that it receives only atmospheric metal pollutants. Additionally, as the mire is raised above the mineralised water table, the risk of contamination from the bedrock, and the potential movement of metals after deposition via the movement of water through the sediment, is reduced. Many studies appear to confirm that elements such as copper and lead remain immobile within such ombrotrophic peats (e.g. Kempter and Frenzel 2000; Mighall et al. 2002).

However, other types of soligenous (having a ground-water or slope run-off component as well as rain-fed) mire systems and sediments, such as spring and valley mires have also been shown to have the potential to retain a record of metal pollution, as well as providing information on vegetation change and human activity using techniques such as pollen analysis. In particular, lead appears to not be susceptible to post-depositional mobility, even in non-ombrotrophic peatland (Shotyk 2002). Although care has to be taken to identify potential problems such as mobilisation of metals, and inputs of older material as in-wash, such analyses can be successful. Soligenous bogs have been shown to successfully record changes in, for example, atmospheric pollution related to the steel industry at Tinsley Park, Sheffield (Gilbertson et al. 1997). At Crift Down in Cornwall a record of the environmental effects of prehistoric and historic tin mining and smelting appears to have been retained by the small, soligenous mire. Here the heavy metals are thought to have been supplied to the bog mainly via stream waters as opposed to atmospherically (West et al. 1997). Similarly alluvial sediments from the River Ouse at York in England provided information on lead exploitation from the area from the Roman to the Medieval period (Hudson-Edwards and Macklin 1999). Vegetation change is also successfully recorded at the soligenous mires at Windmill Rough and Middle North Combe in Devon (Ffye et al. 2004), and at Long Breach and Gourte, Devon (Fyfe et al. 2003).

Chronological Discussion The Mesolithic During the earlier Mesolithic, the area around the sampling site was dominated by forest. Corylus may have been growing as a canopy tree as well as forming dense scrub, and Ulmus and Quercus, would dominate the denser lower-lying woodland. An open woodland of Betula and Pinus may have existed on the thinner, higher altitude soils, with some suggestion of a ground cover of ericaceous plants, and the occasional Sorbus. However, Quercus petraea (sessile oak) is also able to colonise higher altitudes and a Betula-Quercus-Pinus woodland may also have developed on the upland and hillslope areas (Walker 1982). Salix may have formed a component of wet woodland in the valley bottom, or as Salix herbaceae (dwarf willow) formed a ground cover in the more open upland areas.

19 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Few open areas exist, although some grass may have fringed the water-course. In general terms the lack of herbs reflect the closed nature of the wooded landscape. However, locally in the upland area, the Betula-Pinus woodland provides a more open habitat, and those herbs present such as Achillea (yarrow) reflect the immaturity and disturbed nature of the young, mineral soils.

The presence of a dense layer of wood beneath this sample implies the existence of a fallen tree. That a clearing may have been created by such an event is further emphasised by the super-abundance of Osmunda regalis spores. Osmunda is a deciduous herbaceous fern common to the banks of streams, woodland bogs, and acidic wetlands. Experiments have shown that light promotes the fertility of the fern, with the production of fertile, sporangia- bearing fronds increasing under increased light conditions (Landi and Angiolini 2010). A fallen tree within an otherwise relatively densely wooded area would therefore create ideal conditions to promote the fertility of the fern, and thus the super-abundance of spores as noted in the analysis.

Later in the Mesolithic the landscape is still predominantly wooded. The increase in Corylus and Quercus may reflect their expansion onto those areas formerly occupied by Pinus and Betula, as soil fertility and climatic conditions improve. However, locally an increase in sedge-rich open areas is demonstrated, with associated herbs such as Filipendula, Succisia and Ranunuculus. Achillea and Solidago may form part of the general grass-sedge-land community, but they often prefer disturbed, fresh soils and may indicate local disturbance or erosion of the well-drained skeletal mineral soils on the surrounding hillslopes. The increase in Cyperaceae, accompanied by the occurrence of Equisteum and increased Sphagnum spp. spore deposition, suggests a period of increased wetness. This may indicate the transition to the wetter conditions of the Atlantic period, although equally, local changes in the mire development and hydrology may be responsible for these changes.

Later still in the Mesolithic we see the earliest evidence for the development of an alder carr on the site, although its origins are undoubtedly somewhat earlier. The carr persists in the area throughout the later Mesolithic and subsequent Neolithic periods. A peak in microscopic charcoal deposition suggests increased burning in the area, which may be natural or anthropogenic in origin. Burning of the vegetation during the Mesolithic period has been much discussed, and examples from Wales and elsewhere in the British Isles are well- documented (Innes, Blackford and Simmons 2010; Ryan and Blackford 2010; Walker et al. 2006). A more intensive use of the uplands of northern England c.6800 C14 years BP by Mesolithic populations has been suggested (Spikins 1999), and it is possible that a certain degree of resource stress from a growing human population was enforcing a more proactive and intensive management of the landscape in other regions, including Wales.

There is a considerable body of evidence to suggest that human-induced burning by hunter- gatherers was probably used to control the movement of herds of large grazing mammals. Fire could be utilised to physically direct herds, but also to create clearings and open ground which would encourage grazing and facilitate hunting, as well as increasing the range and variety of edible plant foods for humans. It is thought that such burning could also promote the expansion of Corylus. Regrowth after burning could rejuvenate Corylus shrubs and encourage increased flowering and thus hazelnut production. Hazelnut shells are a consistent presence on Welsh Mesolithic sites, and the nuts appeared to have formed an important resource during this period. Additionally Corylus is an opportunistic species which would rapidly colonise and expand over any open ground recently cleared, (Bell and Walker 2005;

20 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Ingrouille 1995, 173-175; Mighall and Chambers 1995, 313; Walker et al. 2006). At Clogwynygarreg however, Corylus appears to decline during the episode of implied burning, although the limits of the sampling in the assessment prevent detailed examination of this phenomenon. Possibly the burning of Corylus growing on the thinner soils of the hillslopes and upland area, may have led to deterioration of soil fertility, and encouraged the recolonisation of these areas by Pinus and Betula, and indeed ericaceous species. The presence of Chamaenerion angustifolium (rosebay willowherb), further indicates that burning may have taken place close to the sampling site. Although a native of rocky places and damp woods, it thrives in cleared ground, especially where burning has taken place (Mabey 1996). Burning activity may also be responsible for the noted increase in ericaceous pollen. Certain ericaceous species such as Calluna vulgaris flourish after burning, taking particular advantage on thinner, acidic soils.

The transitional period between the later Mesolithic and the Neolithic witnesses the final maximum of tree and shrub cover in the area of the sampling site, in no small part due to the dominance of the alder carr on the pollen record. However, Corylus has also now expanded at the expense of other tree species. Although some of these changes may be explained by the relative nature of the analysis, the suggestion is that much of the local Quercus and Ulmus woodland is diminishing and being replaced with Corylus scrub. Pinus too seems affected. Hydrological changes associated with the expansion of the alder carr may account for some of the variation. Cyperaceae too shows a small increase, indicating the possible expansion of wetter areas across the basin. Microscopic charcoal deposition values are low, implying burning is not taking place at this time. However, with the wide sampling interval, it is possible that an earlier burning event, not noted in this sample, has encouraged the expansion of hazel scrub into formerly cleared areas.

Neolithic and Bronze Age The Neolithic period in Britain is noted generally for an increased human impact upon the landscape, involving clearance of woodland and scrub, evidence for cultivation and pastoralism, and increased archaeological evidence for settlement and ritual activity. As may then be expected, the area around Clogwynygarreg is becoming increasingly open during the Neolithic, with evidence for increased clearance of the dryland woodland, and the expansion of open, grassy areas. The development of open grassland is indicated by increasing values for Cyperaceae and Poaceae. The presence of Plantago lanceolata (ribwort plantain) and Potentilla strongly imply grazing activity in the area. It is thought that grazing may be particularly beneficial to the flowering of Potentilla erecta (tormentil), (Moore et al. 1986), and P.lanceolata is recognised as a key indicator of pastoralism. Additionally, the presence of cereal-type pollen, albeit in trace amounts, suggests cultivation was also taking place within the local area. Cereal pollen grains are poorly dispersed and are not though to travel far from their source (Hall 1989).

Some drying of the mire is implied by the pollen evidence in this sample. The alder carr has contracted and Betula has expanded into the drier areas. This is generally consistent with the transition from the wetter conditions of the Atlantic period to the more continental conditions of the Sub-Boreal. Aside from the expansion in Betula, wooded areas have now declined, although diversity in the tree species has increased. The disappearance of Ulmus from the profile at this point is consistent with the elm decline, a widespread phenomenon dated throughout Wales to c.5000BP. The elm decline has been widely discussed, and is thought to

21 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

have been caused by a combination of anthopogenic and natural factors including clearance, grazing and foddering of stock, and disease.

The appearance of Tilia (lime), albeit represented by a single pollen grain only, is interesting. Tilia is a thermophilous species, requiring mean August temperatures of 20oC in order to produce fertile seed, and preferring richer mor soils (Piggott and Huntley 1978; 180). It is also insect-pollinated, and is thus thought to be somewhat underrepresented in pollen diagrams as it produces less pollen per tree than wind-pollinated species. Tilia is thought to have become established in Wales by c.6000 BP, but was only abundant in eastern lowland sites, with a much more restricted occurrence elsewhere (Caseldine 1990, 34). Its presence in the Clogwynygarreg sample suggests it was growing close to the sampling site at this time, and conditions in terms of mean temperatures and fertility of the soil, were thus favourable for its establishment. Tilia is a useful fodder crop, and also provides important fibres for cordage from the bast from the inner bark (Godwin 1984, 160-164; Mabey 1996, 116-119).

In the two samples relating to the Neolithic–Bronze Age transitional period, and the later Bronze Age, burning activity has increased, as demonstrated by increases in microscopic charcoal deposition. Generally the local dryland wooded areas are declining, as open grassland increases. In the earlier phase the reappearance of Chamaenerion angustifolium again reflects the presence of open areas cleared by burning. The later Bronze Age sees a mosaic of scrub and open grassland on the valley sides. Although burning may still be implicated as a clearance mechanism, increased pastoral activity, as indicated by the presence of grassland containing Plantago, Rumex and Potentilla, would also assist in impeding regeneration of woody species. Despite the general decline in woodland, both Corylus and Fraxinus exploit the increase in newly cleared areas, and flourish in the lighter conditions, creating areas of scrubby woodland. The presence of Ilex pollen may indicate an increase in soil erosion, as may be expected from increased clearance and grazing. Ilex pollen is poorly dispersed and is more abundant in more minerogenic deposits where forest clearance has resulted in soil erosion (Moore et al. 1986). Levels of lithogenic elements associated with soil dust, such as iron, silicon and titanium do not however record an increase during this period, suggesting that erosion if present, is slight.

The increasing impacts during the Bronze Age, as evidenced in the pollen and charcoal record, are consistent with the increase in archaeological evidence for human activity in the area. The proximity of the recently identified burnt mound close to the sampling site is particularly relevant as it implies settlement close to the bog. Burnt mounds are a common site type of Ireland and many parts of Britain, and generally date to the Bronze Age, although slightly earlier and later examples are known. They are thought to have been created from the use of hot stone technology to heat water for a variety of purposes, including cooking, bathing, laundering or industrial use. At Parc Bryn Cegin, Llandegai near Bangor in North Wales, charcoal from several burnt mounds identified hazel as the prime fuel wood used in the mounds, along with some oak. Wood was also used structurally in the mounds as troughs to hold the water, and in stake walls, possibly acting as supports for a shelter or wind-break (Fluke and Kenney 2008, 51-67).

Exploitation of the copper resources of the area during the Bronze Age is not directly identifiable in this assessment, although that does not preclude its occurrence. Although the geochemical evidence is inconclusive for this period, further pollen and charcoal analysis would enable a more precise examination of the changes and activity taking place here. Certainly increases in microscopic charcoal deposition, and declines in those woody species

22 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

which may be most desired as fuel sources can be identified, but as we have seen, a range of activities may account for the changes noted in the record.

Interestingly the expansion of heather moorland, commonly identified from the Bronze Age from sites throughout Wales, is not recorded in this assessment. Associated factors, such as increased burning activity, clearance and grazing are however identified. It is therefore suggested that the development of heath conditions did not occur at Clogwynygarreg until some time after c.2600BP.

The Historic Period - The Geochemical Record The geochemical record has been described for the upper 1m of the core, and it has been noted that in general terms the elemental curves remain relatively constant below 0.40m. Changes noted in the geochemical curves reflect changes in the later periods, which, owing to the limits of the assessment, and the rather surprising early dates for the core, have not been analysed for pollen and microscopic charcoal deposition. This is unfortunate but could be addressed through further work on the upper areas of the core.

It has already been noted that changes in the geochemical record attributable to mining and metallurgical activities were not identified during the prehistoric period. An increase in lead deposition during the Roman period is only subtly identified, suggesting that industrial and other activities were not intense in this area during this period, and that these changes may have a more regional origin. During the Medieval period however, the increase in deposition of lead and other heavy metals is more pronounced. This corroborates the historical evidence documenting metallurgical activities in the local area around Drws y Coed. In addition increased clearance of woodland for fuel as well as agricultural activities would increase soil dust deposition through erosion. It is during the Industrial Period that the first convincing increases in copper deposition occur, presumably reflecting the intensification of the copper mining and processing activities at Drws y Coed. Lead deposition also peaks during this period, before declining to present day, reflecting changes in fossil fuel composition (e.g. unleaded petrol).

23 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

10. CONCLUSIONS AND RECOMMENDATIONS FOR FURTHER WORK

The assessment of the core from the mire at Clogwynygarreg provided a broad picture of vegetation and landscape change within the area from the Mesolithic period to the present day. The pollen and microscopic charcoal record appears consistent for the periods assessed, and the geochemical evidence suggests a reliable record of heavy metal deposition for at least the last two millennia.

During the Mesolithic the area was predominantly forested. A burning event during the Mesolithic is suggested by an increase in microscopic charcoal deposition, indicating probable human activity in the area, and contributing to the increasing body of evidence for relatively widespread manipulation of the environment by Mesolithic people. From the Neolithic onwards there is evidence for increasing impacts upon the local environment by humans, as woodland cover reduces and changes in composition, and open grassland areas increase. The geochemical record hints at increased industrial activity producing higher pollutant inputs from the Roman period on, although this may be of a regional nature. Certainly, there is clearer evidence for Medieval industrial activity within the area, increasing th th through time to the known exploitation of the Drws y Coed mines in the 18 and 19 centuries.

Although this assessment was not refined enough to demonstrate in detail changes over time, it has provided a foundation upon which to base further work. Additional dating is essential to refine the chronology and elucidate in particular the upper 1m horizons. These areas are key to examining the later prehistoric, medieval and post-Medieval landscapes, and attempting to more fully describe potential impacts from mining and metallurgical practices.

In addition to further examining this core, it would be useful to assess the other mires identified in the Drws y Coed area in order to provide a comparable record with the core from Clogwynygarreg. The valley mire (Mire 2) to the west is situated downstream from the main mining areas and as such would receive pollutants in stream water. As discussed, although potentially problematic, it is possible that a record of these inputs may be retained by the mire and thus provide a complimentary record to that already acquired. The mire adjacent to the prehistoric settlement immediately upslope to the north of the mining area (Mire 3) would similarly allow comparison of the record from another mire type, and contribute to the body of evidence for landscape change and human activity in the area.

10. ACKNOWLEDGEMENTS

The author would like to thank the following individuals for their assistance in the completion of this project: Mr Alwyn Hughes, Mr Owen Geraint Ellis, S. Williams and D. Leighton, (RCAHMW); Raymond Roberts (CCW), Astrid Caseldine, Dr. Ralph Fyfe, Dr. John Ince, John Roberts (Snowdonia National Park), Dr. D W Shimwell; Ian Grant; John Moores and Dr. Peter Ryan, (University of Manchester).

24 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

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29 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

APPENDIX I: Radiocarbon Dating Reports

Scottish Universities Environmental Research Centre Director: Professor R M Ellam Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride, Glasgow G75 0QF, Scotland, UK Tel: +44 (0)1355 223332 Fax: +44 (0)1355 229898 www.glasgow.ac.uk/suerc RADIOCARBON DATING CERTIFICATE 13 September 2012

Laboratory Code SUERC-41892 (GU28003)

Submitter Fiona Grant Ardea Palaeoenvironmental and Archaeological Services 8 Coed y Glyn Glyn Ceiriog Llangollen, LL20 7NR

Site Reference Clogwynygarreg

Sample Reference CLOG2052

Material Peat : Humic Acid dated

δ13C relative to VPDB -31.2 ‰

Radiocarbon Age BP 2146 ± 24

N.B. The above 14C age is quoted in conventional years BP (before 1950 AD). The error, which is expressed at the one sigma level of confidence, includes components from the counting statistics on the sample, modern reference standards, background standards and the random machine error.

The calibrated age ranges are determined using the University of Oxford Radiocarbon Accelerator Unit calibration program OxCal 4.1 (Bronk Ramsey 2009). Terrestrial samples are calibrated using the IntCal09 curve while marine samples are calibrated using the Marine09 curve.

Samples with a SUERC coding are measured at the Scottish Universities Environmental Research Centre AMS Facility and should be quoted as such in any reports within the scientific literature. Any questions directed to the Radiocarbon Laboratory should also quote the GU coding given in parentheses after the SUERC code. The contact details for the laboratory are email [email protected] or Telephone 01355 270136 direct line. Conventional age and calibration age ranges calculated by :- Date :-

Checked and signed off by :- Date :-

The University of Glasgow, charity number SC004401 The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336

1 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Calibration Plot

2400 SUERC-41892 (2146,24) 68.2% probability 346 (16.2%) 321caiBC 206 (45.3%) 162caiBC 2300 CL' 131 (6.6%) 119caiBC @. 95.4% probability c 0 2200 353 (24.5%) 296caiBC c 230 (1.5%) 220caiBC

....E 211 (69.4%) 95caiBC Q) a; '0 2100 c 0 -e <11u 0 2000 :0 <11 a:: 1900

1800

Calibrated date (caiBC/caiAD)

2 Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales Scottish Universities Environmental Research Centre Director: Professor R M Ellam Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride, Glasgow G75 0QF, Scotland, UK Tel: +44 (0)1355 223332 Fax: +44 (0)1355 229898 www.glasgow.ac.uk/suerc

RADIOCARBON DATING CERTIFICATE 13 September 2012

Laboratory Code SUERC-41893 (GU28004)

Submitter Fiona Grant Ardea Palaeoenvironmental and Archaeological Services 8 Coed y Glyn Glyn Ceiriog Llangollen, LL20 7NR

Site Reference Clogwynygarreg

Sample Reference CLOG2206

Material Waterlogged Wood : -

δ13C relative to VPDB -31.9 ‰

Radiocarbon Age BP 8525 ± 27

Conventional age and calibration age ranges calculated by :- Date :-

Checked and signed off by :- Date :-

The University of Glasgow, charity number SC004401 The University of Edinburgh is a charitable body, registered in Scotland, with registration number SC005336 1

Assessment of a Peat Core from Clogwynygarreg, Snowdonia, North Wales

Calibration Plot

RC-41893 (8525,27) 8700 68.2% probability

7586 (47.5%) 7568caiBC 7562 (20.7%) 7551caiBC CL' 95.4% probability @. 8600 7592 (95.4%) 7537caiBC c 0

c E ... Q) 8500 a; "c 0 -e

0 :0 8400

8300

Calibrated date (caiBC)

Z CLOG2 0.10-1.60 AI int. Si int. Pint. S int. Clint. K int. Tiint. Mn int. Feint. ilo coh/Mo in• (mm) 100

150

200

250

300

350

400

450

500

550

600 :g t r:l 650 z

700 t:l

750 ><:

800 - - 850 g 900 ffi 950 s. 1000 0

1050

1100

1150 l[i!l.

1200 1Jl

1250

1300

1350

1400

1450

1500

1550

Core: CLOG20.10·1.60 Section:CLOG2 0.10-1.60 User:hfl Date: 08/06/2012 X-Ray tube:Mo target Line camera signal148654 at 25 ms Filename:CLOG 2 0. 10-1.60 Data produced by the AIGES ltrax XRF Conditions 30 kV 30 rnA S tep Size: 800 mci rons Count·time: 30 seconds/increment X-r adio ra h Conditions 45 kV 50 rnA S te Size: 800 microns Dwell time: 200 ms/increment

Z CLOG2 0.10-1.60 Se int. Br int. Rb int. Sr int. Zr int. Pb int. Th int. Mo inc Mo coh ilo coh/Mo in•

150

200

250 ;J> lfl 300 lfl 350

(1)a 400 ...... 450 = 0 ...... 500 ""d 550 (1) Ia 600 n ....,0 650 (1)

700 ::p 0 750 3

800 n

850

900

950

1000

1050 l til 1100 = 1150 g. 1200 _=F* 1250

1300 ....,&

1350 g.

1400 E. 1450 (1) lfl

1500

1550

Core: CLOG2 0.10-1.60 Section: CLO G2 0.10-1.60 User:hfl Date: 08/06/2012 X-Ray tube:Mo target Line earnera sgi nal148654 at 25 ms Fi ename:CLOG 2 0.10-1.60 Data pr oduced by theAIGES ltrax XRF Conditions 30 kV 30mA Step Size: 800 mci rons Count-time: 30 seconds/increment X·radioora h Conditions 45 kV 50mA Ste Si ze: 800 microns Dwell time: 200 ms/increment

z CLOG2 1.10 - 2.10 AI int. Siint. Pint. S int. Clint. K int. Ti int. Mn int. Feint. Mo inc ()

1150

1200 ;J> lfl 1250 lfl

(1)a 1300 .....= 0 1350 ......

'"d 1400 Ia(1) n 1460 ...,0 (1) 1500 ::p 0 3 1550 n

1600 N 1650

1700 l 1750 til = 1800 g.

1850 _=F*

1900 ...,& g. 1950 E. 2000 (1) lfl

2050

Core: CLOG2 1.10 ·2.10 Section: CLO G 2 1.10 ·2.10 User:hfl Date: 11/06/2012 X-Ray tube:Mo target Line camera signal NaN at 25 ms Fi ename:CLOG 2 1.10 ·2. Data pr oduced by theAIGES ltrax XRF Conditions 30 kV 30mA 10 Count-time: 30 seconds/increment X·radioora h Conditions 45 kV 39mA Step Size: 800 mci rons Dwell time: 200 ms/increment Ste Si ze: 800 microns

Z CLOG2 1.10- 2.1 0 Se int. Br int. Rb int. Sr int. Zr int. Pb int. Th int. Mo inc Mo coh o coh/Mo in ( )

1150

1200 ;J> Vl 1250 Vl

(1)a 1300 .....= 0 1350 ......

'"d 1400 Ia(1) n 1450 ...,0 (1) 1500 ::p 0 3 1550 n

1600 w 1650

1700 l 1750 til = 1800 g.

1850 _=F*

1900 ...,& g. 1950 E. 2000 (1) Vl

2050

Core: CLOG2 1.10 · Section: CLOG2 1.10 ·2.10 User: hfl Date:11/06/2012 2.10 Line camera signal NaN at 25 ms Filename: CLO G2 1.10 ·2.10 Data produced by the AIGES ltrax

X-Ray tube:Mo target 30 kV 30mA Step Size: 800 microns Count4time: 30 seconds / ncr XRF Condit ons 45 kV 39 mA S te Size: 800 microns ement D well t me:200 X·radio ra h Conditions ms/increment