Some Aspects of the Pleistocene Succession in Areas Adjoining the English Channel thesis presented for the degree of Doctor of Philosophy in the U n iv ersity o f London hy David Henry Keen A p ril 1975 ProQuest Number: 10098275 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10098275 Published by ProQuest LLC(2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code. Microform Edition © ProQuest LLC. ProQuest LLC 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106-1346 ii A bstract Middle and Upper Pleistocene sea level and climatic successions for the shores of the English Channel are proposed. The sequence is based on the ezamination of an area of fluvial deposition in south Hampshire and an area of marine, colluvial and aeolian deposition in the Channel Islands. Five main conclusions are proposed: I, the terrace gravels of south Hampshire are entirely of fluvial origin and were deposited by the Pleisto­ cene River Solent. These terraces are of end interglacial age and were formed by the large discharges associated with cooling climates, but before glacio-eustatic effects caused sea level to fall greatly from the inter- glacial level; II, the Hoxnian inter glacial sea level was around 100 ft. (50 m.) O.D. not at the much lower levels previously suggested on the basis of evidence from the coasts of the Western Channel; III, an episode of high sea level at around 60 ft. (18 m.) O.D. is dated to a period within the Wolstonian glaciation. It is suggested that this episode may be the "Ilfordian" interglacial tentatively identified in the valley of the lower Thames; IT, the low level rock platforms of the Channel coasts are the result of erosion at several stages of the Middle and Upper Pleistocene; V, the presence of glacial ice in the English Channel at any stage of the Pleistocene is discounted. Correlations and parallels with the Pleistocene sequences of other areas of Britain are suggested. i l l comars Page A bstract 11 Contents i i i - v i Introduction 1 a) South Hampshire I b) Channel Islands 5 PART I 10 Chapter I South Hampshire - an introduction 10 a) Solid geology 10 b) Relief and drainage pattern development 12 Chapter H The Gravel 22 a) Introduction 22 h) Gravel thickness 22 c) Gravel composition and particle shape 24 d) Boulders in the gravel 28 e) Sediment blocks in the gravel 50 f) Current bedding 32 g) Channels in the gœvel 35 Chapter H I The B rickearth 35 a) Introduction 35 b) Thickness 35 c) Structures 36 d) Grains ize 36 e) O rigin 59 Cliapter IT The environmental significance of the gravels and brickearth 42 a) The depositional environment - fluvial or marine 42 t ) The climatic environment 49 c) The fluvial depositional sequence during interglacials 57 Chapter T The stratigraphy and environmental significance of Pleistocene deposits at Stone Point 66 a) Introduction 66 b) Stratigraphy 67 c) Flora {±) Collection and preparation 70 (ii; Palaeoecology 71 iv page d) Mollusca (i) Preparation and identification 75 (ii) Palaeoecology 74 e) Discussion 75 Chapter VI The climatic and ciironological succession in South Hampshire 81 a) Surfaces over I50 f t . (46 m.) 81 b) 100 ft* (30 m.) terrace 81 c) 60 ft* (18 m«) terrace 82 d) 25 f t . (8 m*) terrace 63 e) Post-Ipswichian events 83 Appendix. The age of the break-up of the Wight - Purbeck ridge 87 PART I I 90 Chapter I The Channel I s le s an introduction 90 a) Solid geology 90 b) Effects of deep weathering 91 c) The inclusion of deep weathered material in drift deposits 92 d) Marine plaaation in the islands 93 Chapter II The non-marine P leistocene deposits of the Channel Islands 96 a) The Loess (i) Distribution 96 (ii) Organic remains 98 (iii) Depositional environment 99 (iv ) Age 100 b) The Head ( i j D istrib u tio n 101 (ii) Organic remains 104 (iii) Depositional environment 103 (iv ) Age 109 Chapter III The higher raised beaches 112 a) Introduction 112 b) The 100 f t . (50 m.) raised beach 113 c) The 60 ft. (18 m.) raised beach 117 Chapter IV The 25 f t . (8 m.) raised beach 121 a) Introduction 121 b) Jersey 121 c) Guernsey and the smaller islands to the east 125 d) Alderney and Burhou 128 e) Composition of the 25 f t . (8 m.) raised beach 128 page Chapter T The problem of an e a r lie r low ra ise d beach I 3I Chapter VI Climate and chronological sequence in the Channel Isles I 35 a) Higher surfaces I 35 b) Surfaces and deposits between 125 ft. (37«7 m.) and 85 f t . (26 m.) I 35 c) Features post-dating the deposition of the 100 f t . (30 a.) beaches I 56 d) The age o f th e 60 ft. (18 m.) beach and features associated with it I 38 e) The age of the 25 ft, (8 m.) beach I 4I f) Features post-dating the 25 ft. (S m.) bm,ch I 44 PART I I I 146 Chapter I The Hoxnian of the English Channel - some correlations and problems I 46 a) Introduction I46 b) Hoxnian deposits in Hampshire and the Channel Isles 147 c) A review of some Hoxnian sites dated by organic n%ans 147 d) The problem of the Hoxnian sea level in western Britain I 50 e) Correlations between Hoxnian deposits and the areas under examination 153 f) The problem of the true age of the Hoxnian 154 Chapter I I The separate existence of a 60 ft. (18 m.) sea level and scmie correlations 157 a) Introduction 157 b) Evidence for a 60 ft. (18 m.) beach and terrace in the areas under discussion 157 c) Some probable sites for the 60 ft. (18 m.) beach and terrace in Britain 158 d) The age of the Ilford terrace 159 e) The age of the 60 ft. (18 m.) deposits of the Channel Isles and soith Hampshire 162 Chapter III The Ipswichian interglacial and the 25 ft. (8 m.) sea level I 64 a) Introduction I64 b) The 25 ft. (8 m.) beach aM terrace in the Channel Isles and south Hampshire I 64 o) Some sites dated as Ipswichian and associated with evidence of the 25 ft. (8 m.) sea level I 65 d) SoEfâ correlations between the Channel Isles and south HaEg>shire 168 Vi page Chapter I? A summary of Kiddle and Upper Pleistocene sea levels and climates in the English Channel I 7 I Appendix A I74 A cknowledgaent s I76 Bibliography I77 - 198 F igures I99 - 200 P la te s 201 - 202 Tables 203 Total no. of pages in text 209, + 42 fig u re s, 55 p lates & 6 tab les * Chapter T, Part I, forms the text of a paper published in the Proceedings of the Geologists* Association, vol.86, 1975, by B.C. Brown, D.B. Gilbertson, C.P. Green and the present author. Parts of the chapter not written by the present author are marked in the text. Introduction The object of this study is to recognise the sequence of changing climate and sea level in the Middle and Upper Pleistocene for areas in southern Britain unaffected by glaciation. Accordingly two areas on the shores of the English Channel are examined, the New Forest, an area of mainly fluvial and estuarine deposition, and the Channel Isles, an area of mainly marine aM periglacial deposition. In these two areas many of the typical characteristics of non-glacial Pleistocene deposition can be recognised. Several sites dated archaeologically or by pollen analysis provide the basis for an absolute chronology. An attempt is also made to provide a generally applicable statement on the nature and sequence of marine and fluvial deposition at the end of interglacials and thus on the origin of Pleistocene river terraces and on the inter-relationship between climatic change and the change in sea level. a) South Hampshire In Hampshire the area chosen for study is the southern New Forest from Southampton Water in the east to the valley of the Avon in the west. The northern limit of the area studied is approximately that of the Bournemouth to Southampton railway line. In this area may be found the large tracts of gravel and brickearth with which the first part of this study is concerned. The southern boundary of the area studied lies mostly beneath the water of Christchurch and Poole Bays but the largest remnant of the south bank of the Pleistocene River Solent, the Isle of W i^t, Is also included in the area studied. The area is portrayed on sheets 179 and 180 of the Ordnance Survey’s one inch series. In view of the fragmen­ tary nature of the evidence for Lower Pleistocene deposition only deposits below 130 f t . (40 m.) were closely studied so that this account is pri­ m arily one of Middle and Upper P leistocene events. Below I 30 ft. (40 m.) extensive terrace surfaces occur and almost all the available sections are below this height while above 1)0 f t .