Sourcing the Clay: Iron Age Pottery Production Around Poole Harbour and the Isle of Purbeck, Dorset, UK Volume 1 of 2 Grace Perp
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Sourcing the clay: Iron Age pottery production around Poole Harbour and the Isle of Purbeck, Dorset, UK Volume 1 of 2 Grace Perpetua Jones A thesis submitted in partial fulfilment of the requirements of Bournemouth University for the degree of Doctor of Philosophy May 2017 Bournemouth University in collaboration with The Poole Harbour Heritage Project Copyright statement This copy of the thesis has been supplied on condition that anyone who consults it is understood to recognise that its copyright rests with its author and due acknowledgement must always be made of the use of any material contained in, or derived from, this thesis. ii Sourcing the Clay: Iron Age Pottery Production around Poole Harbour and the Isle of Purbeck, Dorset, UK Grace Perpetua Jones Abstract One of the most ubiquitous types of Romano-British coarseware pottery, Black- burnished ware 1 (BB1), was produced around the shores of Poole Harbour, in South East Dorset. Previous researchers have shown that this industry was already well- established by the 1st century BC, while reports documenting excavations at earlier Iron Age sites in Dorset indicate that its roots can be traced back to around 700 BC. However, little is known about the production and circulation of wares during these formative phases of the industry, a topic that is addressed by the research presented here with a specific focus on the clays selected by potters working between 700 BC and 100 BC. A typology of Iron Age Poole Harbour wares has been compiled, drawing together the range of forms found on sites across Dorset. A programme of fieldwork revealed that the landscape of Poole Harbour and the Isle of Purbeck offered a range of clays and sands to the potters. Petrological analysis of 255 sherds of pottery illustrated that the Poole Harbour ware fabrics are characterised by the presence of elongated argillaceous inclusions and a low incidence of silt-sized quartz, with variability in the range of larger quartz grains. Thin sections of 105 clay samples revealed the silt content of the clays is greater than that of the pottery, suggesting potters levigated the raw clay rather than simply utilising a naturally sandy clay. Examination of the elongated argillaceous inclusions in the pottery, using petrology and a scanning electron microscope with energy dispersive X-ray spectroscopy, indicated they are a component of the clay rather than shale fragments added as temper. Compositional analysis of 100 samples of pottery and clay, using inductively coupled plasma spectrometry, demonstrated the potters selected the iron-rich, red- firing clays, rather than the malleable white-firing clays. It also revealed that during the earlier Iron Age the potters utilised the Wealden Clay deposits from the southern side of the Purbeck Ridge, but exploited the Poole Formation clays to the north during the later Iron Age. The wider cultural context of this change is considered and it is suggested that shifting settlement patterns may have influenced the location of the expanding production sites and their ties to communication networks. iii Table of contents Volume 1 Chapter 1. Introduction 1 1.1 The Iron Age and Romano-British pottery of Dorset 2 1.2 Aim and objectives of the research 4 1.3 Chronological scope of the project 5 1.4 Structure of the thesis 6 Chapter 2. Background: geoloy, previous work and considerations of ceramic provenancing 7 2.1 The geology and topography of the Poole Harbour region 7 2.1.1 Sea-level change 8 2.1.2 Geology 9 Jurassic Period 10 Cretaceous Period 10 Palaeogene Period 11 Quaternary deposits 16 Economic geology 17 2.2 Archaeological Investigation of Pottery Production in south-east Dorset 17 2.3 Mineral and chemical analysis 19 2.3.1 Heavy mineral analysis 20 2.3.2 Petrology and Neutron Activation Analysis 23 Jennifer Grant 23 Belinda Coulston 24 Lisa Brown 28 Other researchers 29 2.4 Ceramic provenancing 29 2.4.1 Choice of instrumentation 31 2.4.2 Dilution effect 32 2.4.3 Data analysis 33 2.5 Conclusion 34 Chapter 3. Pottery and brick production around Poole Harbour and Wareham 37 3.1 Prehistoric and Romano-British pottery production 37 3.1.1 Bronze Age pottery production at Bestwall Quarry, Wareham 37 iv 3.1.2 Early to Middle Iron Age pottery production 38 3.1.3 Late Iron Age and Romano-British pottery production 42 Late Iron Age to early Romano-British production 42 Pottery production during the 2nd to 5th centuries AD: firing structures 47 Other features associated with pottery production during the 2nd to 5th centuries AD 56 3.2 Interpreting the archaeological evidence 60 3.2.1 Location 60 3.2.2 Fabric 61 3.2.3 Vessel formation 61 3.2.4 Firing technology 62 3.2.5 Firing temperature 64 3.2.6 Wasters 64 3.2.7 Fuel 64 3.2.8 The colour conundrum 65 3.2.9 Potters’ equipment 69 3.3 Medieval pottery production 69 3.4 Clay Exploitation in the 17th to 21st Centuries 70 3.5 Production of pottery and architectural ceramics during the 19th to 21st centuries 71 3.5.1 Exploitation of the different clay members of the Poole Formation 71 3.6 Conclusion 73 Chapter 4. The ceramic assemblages sampled for analysis 77 4.1 Sites located around Poole Harbour and its hinterland 79 4.1.1 Wytch Farm Oilfield 79 4.1.2 Green Island 83 4.1.3 Redcliff Farm 85 4.1.4 Bestwall Quarry, Wareham 86 4.1.5 East Holme 87 4.2 Sites to the south of the Purbeck Ridge 88 4.2.1 Eldon’s Seat, Encombe 88 4.2.2 Rope Lake Hole 90 4.2.3 Quarry Field / Football Field, Worth Matravers 93 4.3 Sites in west Dorset 95 4.3.1 Maiden Castle 95 v 4.3.2 Southdown Ridge, Weymouth 99 4.4 Sites in east Dorset 102 4.4.1 Hengistbury Head 102 4.5 Sites in north Dorset 104 4.5.1 Gussage All Saints 104 4.5.2 Barton Field, Tarrant Hinton 110 4.5.3 Bradford Down, Pamphill 111 4.5.4 Oakley Down, Wimborne St. Giles, Dorset 112 4.6 Sites in north-east Dorset and Somerset 114 4.6.1 Allard’s Quarry, Marnhull 114 4.6.2 Sigwells, South Cabury Environs 118 4.7 Conclusion 119 Chapter 5. Fieldwork 125 5.1 Methodology 126 5.2 Results 129 5.2.1 Creekmoor Clay 129 Upton Country Park 129 5.2.2 Oakdale Clay 130 Sandford 130 East Holme 131 Longfleet Lodge 131 Upton, Poole Road 132 5.2.3 Broadstone Clay 133 South of Bramble Bush Bay 133 Ower Bay 135 Newton Bay 136 Arne Peninsula 137 Arne, South of Bank Gate Cottages 138 Arne Beach 138 Godlingston Heath 139 Redcliff Farm, Ridge 141 Foxground Plantation 141 Rempstone Heath 142 Sandford 143 Wytch Heath 143 5.2.4 Parkstone Clay 144 vi Brownsea Island 144 Creech Heath 147 Alderney, Newtown and Foxholes 148 Bourne Bottom Local Nature Reserve and Alder Hills Nature Reserve 151 5.2.5 Poole Formation 153 Furzey Island 154 Green Island 154 Round Island 155 5.2.6 Wealden Clay 156 Belle View Farm 156 Lower Lynch House 157 South-east Purbeck 159 5.2.7 Kimmeridge Clay 160 5.2.8 Barton Clay 160 5.3 Summaries of the sampled clay types 161 5.3.1 Creekmoor Clay 161 5.3.2 Oakdale Clay 161 5.3.3 Broadstone Clay 161 5.3.4 Parkstone Clay 163 5.3.5 Poole Formation 164 5.3.6 Wealden Clays 164 5.3.7 Kimmeridge Clay 165 5.3.8 Barton Clay 165 5.4 Conclusion 165 Chapter 6. Petrological analysis of pottery samples 167 6.1 Harbour sites and hinterland 167 6.1.1 Green Island, Poole Harbour 168 6.1.2 Wytch Farm Oilfield sites 170 6.1.3 Redcliff, Ridge 172 6.1.4 Bestwall Quarry, Wareham 173 6.1.5 East Holme 174 6.2 South of the Purbeck Ridge 175 6.2.1 Eldon’s Seat, Encombe 175 6.2.2 Rope Lake Hole, Kimmeridge 176 6.2.3 Football Field, Worth Matravers 180 vii 6.3 West Dorset 182 6.3.1 Maiden Castle, Dorchester 182 6.3.2 Southdown Ridge, Weymouth 187 6.4 East Dorset 190 6.4.1 Hengistbury Head, Bournemouth 190 6.5 North Dorset 191 6.5.1 Gussage All Saints 191 6.5.2 Barton Field, Tarrant Hinton 196 6.5.3 Bradford Down, Pamphill 197 6.5.4 Oakley Down, Wimborne St. Giles 197 6.6 North-east Dorset and Somerset 199 6.6.1 Allard’s Quarry, Marnhull 199 6.6.2 Sigwells (South Cadbury Environs) 203 6.7 Conclusion 205 Chapter 7. Petrological analysis of the clay samples, and comparison of the pottery and clays 209 7.1 Petrological analysis of the clay samples 209 7.1.1 Poole Formation 210 Round Island 210 Furzey Island 210 Green Island 210 7.1.2 Broadstone Clay 211 Arne Peninsula 212 Ower Bay 212 South of Bramble Bush Bay 213 Redcliffe Farm 213 Foxground Plantation 213 Wytch Heath and Rempstone Heath 214 Godlingston Heath 214 Sandford 215 7.1.3 Creekmoor Clay 215 7.1.4 Oakdale Clay 215 Upton Poole Road 215 Sandford 216 East Holme 216 Longfleet Lodge 216 viii 7.1.5 Parkstone Clay 216 Brownsea Island 217 Bourne Bottom Nature Reserve and Alder Hills Nature Reserve 219 Creech Heath 220 Alderney, Newtown and Foxholes 220 7.1.6 Wealden Clay 220 Belle Vue Farm 220 Lower Lynch Farm 221 SE Purbeck 221 7.1.7 Barton Clay 222 Hengistbury Head 222 7.1.8 Sand 222 7.2 Comparing Clay and Pottery Samples 223 7.3 Conclusion 228 Chapter 8.