The Archaeological Context of Sea Level Change in Prehistoric South Wales
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Changing Tides: The Archaeological Context of Sea Level Change in Prehistoric South Wales Volume 1 Thesis submitted for the degree of PhD Cardiff University Department of Archaeology and Conservation School of History Archaeology and Religion September 2018 Rhiannon Philp DECLARATION This work has not been submitted in substance for any other degree or award at this or any other university or place of learning, nor is being submitted concurrently in candidature for any degree or other award. Signed (candidate) Date: 28/09/18 STATEMENT 1 This thesis is being submitted in partial fulfilment of the requirements for the degree of PhD. Signed (candidate) Date: 28/09/18 STATEMENT 2 This thesis is the result of my own independent work/investigation, except where otherwise stated, and the thesis has not been edited by a third party beyond what is permitted by Cardiff University’s Policy on the Use of Third Party Editors by Research Degree Students. Other sources are acknowledged by explicit references. The views expressed are my own. Signed (candidate) Date: 28/09/18 STATEMENT 3 I hereby give consent for my thesis, if accepted, to be available online in the University’s Open Access repository and for inter-library loan, and for the title and summary to be made available to outside organisations. Signed (candidate) Date: 28/09/18 Summary Evidence for the effects of past sea level change can be found in the submerged landscapes within the intertidal zone of Britain. Such evidence is particularly prevalent in Wales, but understanding the rate at which these changes occurred during prehistory is limited, due to a dearth of palaeoenvironmental, archaeological and temporal data. Wide-scale sea level models cannot provide a high enough chronological resolution to understand sea level change at a human focussed level, causing difficulties when it comes to placing archaeological evidence within its contemporary environmental context. This thesis focuses on the human experience of sea level change and the environmental changes that occur alongside to provide new archaeological, palaeoenvironmental and chronological data from two previously unstudied sites on the Gower Peninsula in South Wales: Broughton Bay and Port Eynon. Focussing on the remains of submerged forests and landscapes in the intertidal zone, this thesis aims to identify localised effects of sea level change on the landscape and the people who inhabited it during prehistory. In doing so it links palaeoenvironmental pollen data from localised environmental sequences with archaeological data from both the immediate vicinity and wider landscape, aided by new radiocarbon dates from the intertidal deposits. The archaeological evidence used includes the human and animal footprints at Port Eynon and securely dated archaeological deposits from the Mesolithic and Neolithic funerary depositions in the wider Gower area. The research also reviews the approach taken to interdisciplinary research within the intertidal zone and proposes solutions to common issues faced in investigating these environments. By combining multiple evidence sources at a localised level, in depth narratives can be drawn about human experience of sea level change in the past, that have the potential to be applied to human experience of current and future sea level driven changes in our own landscapes. Keywords: Mesolithic; Neolithic; footprints; submerged forest; Broughton Bay; Port Eynon; Gower; archaeology, palaeoenvironment; sea level change; pollen. Table of Contents Summary ........................................................................................................................................ v List of Figures ................................................................................................................................ ix List of Tables ............................................................................................................................... xiv Acknowledgements .................................................................................................................... xvii 1 Introduction ............................................................................................................................... 1 Project Overview: .................................................................................................... 3 Specific Research Aims ............................................................................................ 6 Introduction to the study area ................................................................................ 7 South Wales ...................................................................................................... 7 Evidence Base ................................................................................................... 7 Known Deposits ................................................................................................ 8 Study Area ....................................................................................................... 10 Chapter Synopsis ................................................................................................... 13 Chapter 2: Sea Level Change .......................................................................... 13 Chapter 3: A History of Intertidal Archaeology .............................................. 13 Chapter 4: Initial Surveys ................................................................................ 13 Chapter 5: Methodologies .............................................................................. 13 Chapter 6: Results ........................................................................................... 14 Chapter 7: Discussions .................................................................................... 14 Chapter 8: Conclusion ..................................................................................... 14 2 Sea Level Change ...................................................................................................................... 15 Drivers of Sea Level Change .................................................................................. 17 British Holocene Sea Level Change ................................................................. 17 Direct Effects of Sea Level Change ........................................................................ 19 i Land Loss ......................................................................................................... 19 Land Gain ........................................................................................................ 19 Groundwater Levels ........................................................................................ 20 Vegetation Change ......................................................................................... 20 Effects of sea level change in Britain .............................................................. 22 Broad Effects of Sea Level Change in Wales ................................................... 22 Human Response to Sea Level Change in Prehistory ..................................... 23 Archaeological Evidence of Sea Level Change ...................................................... 26 Types of Evidence ........................................................................................... 26 Threats to Intertidal Archaeology ................................................................... 29 Palaeoenvironmental Evidence of Sea Level Change ............................................ 30 Palaeoenvironmental Proxies ......................................................................... 30 Potential Vegetation Communities ....................................................................... 35 Drivers of Vegetation Change ......................................................................... 41 Modelling Sea Levels ............................................................................................. 47 Sea Level Index Points (SLIPs): ........................................................................ 47 Glacial Isostatic Adjustment (GIA) .................................................................. 49 2.6.3 National Sea Level models ........................................................................ 49 Regional Sea Level Curves .............................................................................. 50 A localised approach ....................................................................................... 53 Towards an archaeological context ................................................................ 53 A note on deeper chronologies ...................................................................... 54 Summary................................................................................................................ 55 3 A History of Intertidal Curiosity ................................................................................................ 57 Earliest acknowledgements: ................................................................................. 59 Myth and Legend: .................................................................................................. 60 ii The Atlantis effect ........................................................................................... 60 Welsh examples .............................................................................................. 61 Scientific developments .......................................................................................