University of Plymouth PEARL https://pearl.plymouth.ac.uk 04 University of Plymouth Research Theses 01 Research Theses Main Collection 2013 A Palaeoecological approach to understanding the impact of coastal changes in Late Holocene societies using the Isles of Scilly as a case study Perez, Marta http://hdl.handle.net/10026.1/1957 University of Plymouth All content in PEARL is protected by copyright law. Author manuscripts are made available in accordance with publisher policies. Please cite only the published version using the details provided on the item record or document. In the absence of an open licence (e.g. Creative Commons), permissions for further reuse of content should be sought from the publisher or author. A Palaeoecological approach to understanding the impact of coastal changes in Late Holocene societies using the Isles of Scilly as a case study. By Marta Pérez-Fernández A thesis submitted to the Plymouth University in partial fulfilment for the degree of DOCTOR OF PHILOSOPHY School of Geography, Earth and Environmental Sciences Faculty of Science and Technology August 2013 Marta Pérez-Fernández A Palaeoecological approach to understanding the impact of coastal changes in Late Holocene societies using the Isles of Scilly as a case study. 1 ABSTRACT The overall aim of this thesis was to explore the impact of environmental changes (relative sea level increase and climate) on coastal communities and to investigate how these environmental factors controlled subsistence economies through the Holocene. The hypothesis tested was that relative sea level rise is a key factor influencing location and subsistence strategies of coastal communities throughout the Holocene and that, due to environmental conditions, these changes will be more evident in islands. The Isles of Scilly, located 27 miles off the south west coast of England, provide a good case study for the response of communities to marine inundations and environmental changes. This project aimed also to obtain a high resolution record of vegetation and storminess during the last 3000 years in Scilly, with a robust chronological setting, and also to offer an accurate shape of the coastline of Scilly since the early Holocene. Three terrestrial pollen stratigraphic sequences from the Isles of Scilly were obtained, covering the past 3000 years, from the two main wetland areas of Scilly (one in Higher Moors and two in Lower Moors) with the potential to reveal changing patterns of vegetation reflecting intensity and type of land use. Detailed palaeoenvironmental interpretation has been provided by high resolution pollen analysis. These pollen diagrams suggest that the landscape of Scilly has been an open landscape, heavily managed for both pastoral and arable agriculture since the Bronze Age. There is evidence that the climate during the Holocene period was highly varied. The occurrence of blown sand in the sample cores has been used as an indicator of past storm intensity, by high resolution particle size analysis and Loss-On-Ignition. The three cores show dissimilarities in the storminess indicator during the same periods. It is argued i that this reflects that sand deposition and transport is highly site specific and controlled by topography, sediment availability, wind directions and vegetation cover. An important part of this thesis was to determine the impact of relative sea level rise in Scilly and the extent of the islands over time. A new sea level curve for Scilly has been generated through GIA (Glacial Isostatic Adjustments) using the Bradley et al (2011) method. Palaeogeography maps were produced applying the sea level curve to a new combined bathymetric and topographic model for Scilly. Scilly separated from the mainland around 11500 cal BP, and the islands obtained their modern configuration around 4000 cal BP. The palaeogeography, palaeoecological and the archaeological records of Scilly show that changes in the coastal configuration and storminess had little apparent influence on society from the 1st millennium AD into medieval times. Both, the archaeological and palaeoenvironmental record, have demonstrated that Scillonian societies had a strong resilience and were able to adapt to environmental changes by diversifying their economic strategies and taking advantage of the new conditions, such as new coastal margins. This adaptability was strong until the development of more complex societies and major land reduction conditions that probably led to a tipping point in resilience. There is no apparent discontinuity in land-use on Scilly during the last 3,000 years, although there have been important social and environmental changes. ii 2 Table of Contents 1 ABSTRACT ................................................................................................................ i 2 Table of Contents ....................................................................................................iii 3 ACKNOWLEDGMENTS ...........................................................................................xii 4 AUTHOR’S DECLARATION ................................................................................... xiv 1 INTRODUCTION ....................................................................................................... 1 1.1 AIMS AND OBJECTIVES ................................................................................... 1 1.2 THEORETICAL BACKGROUND ........................................................................ 3 1.3 ISLAND STUDIES .............................................................................................. 6 1.4 USE OF DATES ................................................................................................. 8 1.5 THESIS OUTLINE .............................................................................................. 8 2 LITERATURE REVIEW ............................................................................................10 2.1 PHYSICAL GEOGRAPHY AND GEOLOGY OF THE ISLES OF SCILLY ..........10 2.2 ARCHAEOLOGY IN SCILLY .............................................................................14 2.2.1 Mesolithic (10,000-4000BC) .......................................................................16 2.2.2 Neolithic (4000-2500BC) ............................................................................18 2.2.3 Bronze Age (2500BC-800BC) .....................................................................21 2.2.4 Iron Age (800BC – AD42) ...........................................................................26 2.2.5 Romano-British (AD43-409) ........................................................................30 2.2.6 Medieval (AD410-17th century) and Post-Medieval period ..........................33 2.2.7 Summary ....................................................................................................35 2.3 ENVIRONMENT OF THE ISLES OF SCILLY ....................................................36 2.3.1 Previous palaeoenvironmental work in Scilly ..............................................36 2.3.2 The Early Environment in Scilly ..................................................................38 2.3.3 Mesolithic environment ...............................................................................39 iii 2.3.4 Neolithic environment ................................................................................. 40 2.3.5 Bronze Age environment ............................................................................ 41 2.3.6 Iron Age ..................................................................................................... 42 2.3.7 Historical period ......................................................................................... 42 2.3.8 Summary .................................................................................................... 43 2.4 SEA-LEVEL STUDIES ...................................................................................... 43 2.4.1 Introduction ................................................................................................ 43 2.4.2 Sea-level studies in Southwest England ..................................................... 44 2.4.3 Relative sea-level in the Isles of Scilly ........................................................ 46 2.5 STORMS AND STORMINESS .......................................................................... 49 2.6 SYNOPSIS ........................................................................................................ 52 3 METHODOLOGY ..................................................................................................... 54 3.1 DEVELOPMENT OF A GIS FOR THE ISLES OF SCILLY ................................ 54 3.2 PALAEOECOLOGICAL ANALYSIS .................................................................. 58 3.2.1 Field survey ................................................................................................ 58 3.2.2 Dating methods .......................................................................................... 59 3.2.3 Particle size and Loss-on-ignition ............................................................... 61 3.2.4 Pollen analysis ........................................................................................... 63 3.2.5 Numerical zonation of data ......................................................................... 65 4 RESULTS ................................................................................................................ 66 4.1 PALAEOGEOGRAPHIC MAPPING OF THE ISLES