The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting

G Model PGEOLA 759 No. of Pages 10

Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

Contents lists available at ScienceDirect

Proceedings of the Geologists’ Association journal homepage: www.elsevier.com/locate/pgeola

The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting Vincent J. May c/o Jurassic Coast Trust HQ, Mountfield, Rax Lane, Bridport, Dorset, DT6 3JP, United Kingdom

A R T I C L E I N F O

A B S T R A C T

Article history: Received 3 April 2017 Received in revised form 22 March 2019 Accepted 12 April 2019 Available online xxx

This paper reviews recent studies of the seabed offshore from the Jurassic Coast and discusses their significance for understanding landforms of the World Heritage Site’s Setting as well as adding to understanding of the structures exposed in the cliffs. The processes of coastal formation as sea-levels rose and fell during the Pleistocene and in the recent post-glacial period are critical for this as they reveal the landforms which preserve former shorelines. Detailed surveys of the seabed provide evidence of the low slope of much of this seabed and so enhance the potential to interpret older terrestrial landforms which have been attributed to uplift of former sea beds. Considering both the seabed and the coast from the Pleistocene to the Anthropocene means that it is possible to assess the human impact on these landforms and processes, as well as the natural timescale within which changes occur. The paper describes the seabed geomorphology, relating this, where appropriate, to both the coastal landforms and the exposed structures. Current interpretations of the seabed features and their implications for our understanding of the recent evolution of the Site and Setting are explored. The features of the coast and adjacent sea bed at different phases of the changing coastal environment are discussed to the extent that the available evidence makes this possible, but for much of the area this remains speculative. © 2019 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.

Keywords: Submarine platforms Sea-level rise Erosion Geomorphology

1. Introduction The near-continuous 155 km long Dorset and East Devon Coast World Heritage Site (the “Jurassic Coast”) extends from Exmouth in Devon to Studland in Dorset (Fig. 1). UNESCO’s statement of Outstanding Universal Value emphasizes that the Site has an “outstanding combination of globally significant geological and geomorphological features and contains a range of outstanding examples of coastal geomorphological features, landforms and processes”: qualities which are well managed (May, 2014). Those features, landforms and processes form a continuum with the sea and sea bed which are the focus of this paper. The Site is defined on its seaward side by the Mean Low Water Mark (LWM) and on its landward side by the cliff-top edge or back of the beach. The strata and structures which form the Site continue offshore and together with the landforms behind the cliffs provide an extensive Setting largely moulded between the Pleistocene and the present-day (May, 2008a, 2013). Early discussions about the potential for this area to be designated as a World Heritage Site considered that a potential seaward limit could be the traditional three-mile limit so as to include the

E-mail address: [email protected] (V.J. May).

seabed, even though at that time detailed knowledge of the submarine landscape was limited. However, the need to define the Site by national conservation legal designations, such as National Nature Reserve (NNR) or Site of Special Scientific Interest (SSSI), led to the present much narrower definition being adopted. Although there have been very detailed surveys of the seabed, especially in Weymouth Bay (for example, Donovan and Stride, 1961; Forster, 1961; Heeps, 1986, 1987, 1998; Drayson, 2005) and Lyme Bay (Darton et al., 1981; Nunny, 1995; Antoine et al., 2003), there has been very little interpretation of these surveys to show the nature of the changes which have occurred both at the scale of the whole bay (Fig. 2) or within these areas. However, detailed imagery now available in the DORset_Integrated_Seabed_survey (Dorset Wildlife Trust, 2010) has made it possible to see clearly the detail of this submerged part of the Site’s Setting. May (2013) reviewed these submarine data and this paper builds on that and related studies (May, 2007, 2008a, b). When the Geological Conservation Review (GCR) of coastal geomorphology was being carried out (May and Hansom, 2003), the descriptions of the chosen sites (May, 2003a, b, c, d, e, f) included features, such as the sea bed off Lulworth Cove, which help explain these important parts of the coast, although they were excluded from the GCR and SSSIs because the legislation at the time only allowed designation to LWM (May and Ellis, 2003).

https://doi.org/10.1016/j.pgeola.2019.04.003 0016-7878/© 2019 The Geologists' Association. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

2

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

Fig. 1. Dorset and East Devon Coast World Heritage Site including geographical areas: (i) Old Harry to Durlston Head; (ii) Durlston Head to St Alban’s Head; (iii) Weymouth Bay; (iv) The Shambles; (v) Isle of Portland; (vi) Lyme Bay.

Fig. 2. Weymouth Bay: DORIS Seabed imagery showing depths with yellow and red representing areas above -25 m, green around -35 m and blue below -45 m. Portland Bill is extended by submarine rock platforms to the south-east while the Shambles is a series of sediment sand waves that rest on a submerged rock platform. Note small, meandering channels cut into the seaward edge of the platform (1), which is low cliff similar in depth to the submerged cliff east of Winspit. Also shown: (2) Lulworth Banks anticline (see Sanderson et al., 2017); (a) Isle of Portland; (b) Chesil Beach; and geographical areas (iii) Weymouth Bay; (iv) The Shambles; and (v) Isle of Portland. DORIS maps available on Dorset Wildlife Trust website (Dorset Wildlife Trust, 2010) (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

Recent integrated bathymetric mapping has made it possible to see the relationships and contrasts between the coastal and offshore geology (Kelland, 1975; Westhead et al., 2015, 2017; Sanderson et al., 2017). The relationship between coastal landslides and offshore boulder arcs has been investigated (for example, Badman et al., 1999; McCann and Culshaw, 2001; Gallois, 2011) and provides markers for former cliff line locations. More recently, Brunsden (pers. comm., October 2016) drew attention to the role of recent seabed surveys and imagery in describing the nature of the seabed around Portland Bill (Fig. 2) and across Weymouth Bay to St Alban’s Head and Rose (pers. comm., October 2016) discussed the neotectonic context of the region and its significance in determining, for example, inland peneplains and landslide terrains. Many of the seabed landforms owe their characteristics to the erosion of structures formed after the Cretaceous. The more recent processes of coastal formation as sealevels fell and rose in the glacial and post-glacial periods are critical for this as they reveal the landforms which preserve former shorelines. Describing the sea bed and coast from the Pleistocene to the present day means it is possible to assess the human impact on these landforms and processes, as well as the natural timescale within which changes occur. The most important aspect of the Pleistocene and Holocene is that they are both typified by significant variability in sea-level and changing climate between periglacial and temperate conditions. The relationship between human activity and sea bed activities is not typically recognised by the Holocene and so, where appropriate, reference is made to papers which use the Anthropocene, despite the continuing debate about its validity. 2. The sea bed and coast Although most of the Jurassic Coast is dynamic, with much of the western coast dominated by actively eroding cliffs, there are parts of the coast, especially between Portland Bill and Durlston Head, that preserve emerged beaches and quiescent landslides which demonstrate the resistance of the coast to erosion, especially in the Portland Stone, and where the results of upper cliff failure of the Portland Stone have provided natural rock armouring to the toes of large landslides which currently show very limited failure. However, where the Portland Stone is absent at the coast in both Lyme and Weymouth bays, erosion of former cliffs and the seabed has been active enough to produce a presentday ‘seabedscape’ (May, 2013) which is dominated by low gradients (typically average sea bed slopes between 1 in 400 and 1 in 530). This poses several questions about the breaching, location and timing of the Portland ridge between St Alban’s Head and Portland Bill. The nature and alignment of the coastline both east and west of Portland Bill when sea-level was high enough to create the emerged beaches at Portland remains poorly understood. That the limestone cliffs of Purbeck show no evidence of former beaches and the seabed preserves many small changes cutting into an offshore former cliff line where the local dip means that less thickness of the Portland Stone was exposed provides evidence of the likely location of the Portland Stone outcrop. On the sea bed, complete assemblages of sea bed landforms have only been mapped and imaged within the past century and at the scale of areas such as Weymouth Bay (Fig. 2) only within the past two decades. Few locations have been regularly re-surveyed and so the nature and rates of change are still poorly known and understood. For example, the sand areas of the Weymouth and Lyme Bay sea beds show distinctive ripple patterns, but although the general outline of those areas is well mapped, there is only limited knowledge of the movements of sand and changes in the ripple patterns. Repeat surveys of sand areas (Heeps, 1987) show that there is very little change in the general outline of the sand

3

areas and the ripple patterns except at the ends of the ripples at the edges of the sandbanks. That significant movements of sand are occurring within the sand areas is demonstrated by the disappearance and exposure of rocky strata and boulders between surveys. In broad terms, the seabed can be divided into six geographical areas: (i) The transverse coast and offshore seabed between Durlston Head and Old Harry. This was largely formed as the chalk and limestone ridges between Purbeck and the Isle of Wight were breached and eroded (Velegrakis, 1994; Velegrakis et al., 1999). (ii) The longitudinal coast and sea bed between Durlston Head and St Alban’s Head whose cliffs (both visible and submerged) provide insights into the probable landforms further west before Weymouth Bay was opened up. (iii) In Weymouth Bay the sea bed transgresses the planed strata from Chalk to Portlandian and reveals the features of the Purbeck Anticline. The limestone of the St Alban’s Ledge ridge has been lowered to about 25 m below sea-level. Before the ridge was removed, the landscape would have probably been similar to the coast between St Alban' s Head and Durlston. There would have been two deep valleys within which rivers had cut meanders, one of which had then been cut off to allow the stream to follow a more direct route seawards. Its form is very similar to the abandoned cut-off meander at the Cirque de Navacelles in the French Massif Central (Ambert, 2013). North of the ridge, there is a deep trench (down to -55 m below Chart Datum and about 35 m below the seafloor to its north) associated with the underlying Kimmeridgian clays and shales. This poses questions about how exactly this feature could have formed and its relationship to the landslides at St Alban's Head (Brunsden, 2012). (iv) The Shambles (Pingree, 1978; Bastos et al., 2003a, b) sandbanks on a rock surface at about 35 m depth with ripples averaging 15 m in height to a maximum of 22 m (Fig. 2). A tidal bank formation produced by anticlockwise eddies east of Portland Bill. (v) The Isle of Portland which preserves evidence of both higher and lower sea-levels, with submerged benches which contain channels. There is the question of coastal alignment at some stage prior to the higher sea level evolution of Portland especially the coastal alignment at some stage prior to the higher sea-level at 125,000 years BP (Bastos et al., 2003b). (vi) The predominantly planed sea bed of Lyme Bay with little evidence of deep channels, apart from the drowned channels of the River Exe at the extreme west end of the Site (Durrance, 1969). The submerged rock platforms off the coast west of Lyme Regis are cut across the Triassic and Lower Jurassic strata. Much of the sea bed is covered by sand and gravel deposits (Vaslet et al., 1979), although off the coast west of Lyme Regis there are submerged rock platforms cut across the Triassic and Lower Jurassic strata. The evolution of Lyme Bay, whilst it has been addressed in the west between the Exe and Start Point where there is considerable dateable evidence of both higher and lower sea-levels, is less well investigated in the east of the bay. Much of the coastline was affected by landslides when sea-level was higher, then abandoned when sea-level fell followed by re-activation sea level rose again during the Holocene. Within Weymouth Bay, Drayson (2005) and May (2013) identified 17 sea bed terrain types (Table 1) which, when combined with the DORIS imagery, form six ‘seabedscape’ character types (Table 2). The term ‘seabedscape’ was used (May, 2013) to distinguish these character areas from the term ‘seascape’ used

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

4

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

Table 1 Terrain Types 1–12 (Drayson, 2005) and 13–17 (May, 2013). Terrain type

Terrain description

1. Sediment veneer 2. Sediment overlying bedrock 3. Ripples and waves

Flat generally featureless areas of similar-sized sediment with very little height variation As sediment veneer, but distinguished by low ridges which mask underlying bedrock but not its topography. Extensive areas of sub-parallel ridges, typically up to 0.5 m in height and with consistent wavelength over much of the area of about 2.5 m Curved sand waves up to 15 m high and spaced tens of metres apart. If exposed, would be recognisable as low dune fields Areas which are predominantly sediment, but with many small areas sub-classified as boulders, ledges and sediment veneer

4.Mega-ripples 5. Sediment with intermittent clusters 6. Gravel beach 7. Boulder fields 8. Boulder arcs

Extending to depths exceeding 18 m Extended areas of individual boulders typically up to 5 m across Mark seaward boundaries of landslide. Usually formed of limestone boulders and common today below many high cliffs. Also present up to several kilometres offshore 9. Boulder talus slope Very large boulder slope from above sea level at St Aldhelm’s Head to below 30 m below present sea level 10. Rocky terrace Extensive areas without distinctive linear patterns, but scattered rock debris. 11. Rock ledges Linear and sub-parallel vertical or steep features between 0.3 m and 0.5 m in height. Ledge frequency depends on stratum thickness. Discontinuities occur where there are faults. 12. Ledge surfaces Generally homogenous surfaces with cracks. Abrupt changes to surrounding sediment veneers and ripples. 13. Fault-aligned linear micro- Similar in form to rock ledges, but the face of the feature is controlled by the fault alignment and the upper surface is the dipping surface cuestas of the stratum 14. Channeled rock slopes Hard rock slopes which can be several metres high within which many small channels have been eroded forming the upper catchments of small valleys. Most typical of the Portlandian outcrops south of Purbeck. 15. Incised channels Rare deep and large channels incised into hard rock outcrops 16. Incised meanders Meanders which have been cut deeply into hard rock ridges and include cut-off meanders. 17. Shallow channel in sediment Shallow channels which appear be the result of flows across sandy sediment veneers veneer

Table 2 ‘Seabedscape’ Character Areas. SCA1. Extensive low-angle platforms cut across strata dipping at varying angles. SCA2. Landforms developed under terrestrial (typically periglacial) conditions when the bays were drained by rivers of which the only remnants of their headstreams remain on land. SCA3. Deep valleys with steep west-facing limestone slopes formed by multiple stepped ledges. West of St Aldhelm's Head and Portland Bill SCA4. Sand and shingle ridge and ripple areas, e.g., the Shambles and the sandy western floor of Weymouth Bay. SCA5. Southward-facing slopes marking the locations of coastal slopes which formed in the more resistant strata when sea level was sufficiently static to allow cliffs to form. SCA6. Boulder areas, so named, to distinguish them from boulder fields terrain types (9)

in the C-Scope mapping (LDA Design, 2008). These types can be found within the six geographical areas, but are not coincident with them because the processes which produce them can and do operate within and between the ‘seascape’ areas. To explain the existence and location of these features, it is necessary first to establish the environmental conditions prevailing during the past 125,000 years since sea-level is recorded here at more than 10 m above present levels. It then becomes possible to examine the processes which might have been active enough to mould the features currently visible on the seabed. The key questions about the evolution and character of the seabed are: (i) What climatic conditions, changes in sea-levels and still-stand periods occurred, for how long and with what effect on the now submerged landforms? (ii) How did the submerged platforms develop and what are the implications of the very low angles of slope? (iii) Does the presence of isolated meander patterns provide any clues to the overall development of the seabedscape? (iv) When and how was the Portland–St Alban’s ridge initially breached and the bay subsequently developed into its present form? Despite the greatly increased information and imagery about Lyme, Weymouth and Poole bays, it remains difficult to answer all these questions with high levels of certainty. The three bays differ mainly as a result of their geology which has been eroded into gently sloping platforms cutting across the complex structures now revealed in detail by the recent seabed imagery, but Lyme Bay

is, and has been, more open to the sea, compared to Poole and Weymouth bays. The early development of Lyme Bay and the removal of the harder strata, not only of the Portlandian, but also much earlier eras, is not well understood. Unlike the other bays, Weymouth Bay does not have significant river systems draining into and through it, and the drainage pattern there needs further consideration. 3. Pleistocene and Holocene environmental change Changes in sea-level and the associated variation of subaerial processes have been the predominant controls on the evolution of the Jurassic Coast and its geomorphological setting from the Pleistocene to the present day (see Table 3). Davies and Keen (1985) argued that two emerged beaches at Portland show that sea-level relative to the land was between 10 m and 15 m higher about 210,000 and 125,000 years BP. However, although the height and date of the eastern raised beach corresponds well with Marine Isotope Stage (MIS) 5e when sea-level was between 4 m and 6 m OD between roughly 124 and 119 kyr BP according to Rohling et al. (2008), the higher level of the western raised beach is more likely to record uplift of this coastline. After each of those higher sea-levels, the climate cooled becoming increasingly similar to that of the present-day tundra with periglacial processes very active in weathering rock surfaces which were exposed for lengthy periods (certainly in excess of 50,000 years) both between 210,000 and 125,000 years BP and between 125,000 and 6000 years BP (Long and Tooley, 1995). Cryoturbation structures are exposed at Portland Bill and Plateau

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

5

Table 3 Sea-level and climate changes. Years BP 210,000 185,000 to 140,000 140,000 to 125,000 125,000 20,000 14,700 to 12,700 12,90011,800 11,000 10,000 9500 8100 7,500-6,500 5,5003,000 4,500+-70 1014 AD

Local impacts Sea-level about 16 m higher than present (Long and Tooley, 1995; Adams, 2002). Portland ‘western’ raised beach Increasingly cold climate and periglacial processes active on previous seabed. Vertical crustal rise may add to emerged beach altitude. Sea-level falling to about 80 m. Former Weymouth and Lyme Bay sea-beds exposed between -30 and 60 m. Sea-level rising to eastern raised beach level c. 125,000 BP. Sea-level between 7 to 11 m higher than present. Sea-level as low as 120 m and rising at about 10 mm/yr. Bwlling/Allerwd still-stand Global sea-level rose about 16 m during this event at rates between 26–53 mm/ year (Davis et al., 2003; Waller and Long, 2003). 13–15 mm/yr

Portland ‘eastern’ raised beach Gradual flooding of weathered periglacial landscape European precipitation about 0.16 m/yr increasing to c. 0.35 m/yr by about 10,000 BP (Edwards, 2001).

Sea-level about -55 m (Keen, 1998)

Sufficient erosion of exposed Portlandian strata to potentially remove exposed seabed south and west of Portland

Sea-level about -45 m (Davis et al., 2003) Sea-level -29 m (Prestwich, 1892).

Sea-level in Poole Harbour -13 m (Keen, 1996). Sea-level rising

European rainfall about 40% present levels (Paphitis et al., 2010).

Poole Bay palaeovalleys flooded (Brunsden, 2012; Ambert, 2013). Shallow valleys in Weymouth Bay Portland Bill south-east coast cliff line c.-18 m (Bastos et al., 2003a). Boulder arcs 3–4 km offshore (Bray, 1990). Black Ven landslide re-activated (Cooper, 2007).

Peats below Chesil Beach at -3 m and -4.32 m OD St Michael’s Day storm

Gravel deposits on cliff-tops show evidence of similar processes. At the same time as sea-level fell, existing coastal features ceased to be exposed to the high energy wave environment, allowing, for example, once-active landslides to stabilize. Previously submerged sandbanks, such as the Shambles (Pingree, 1978), might survive as dunes, as certainly happens where similar conditions have occurred such as Hudson Bay in Canada. From about 18,000 years BP, sea-level rose at an annual average of 1 mm/yr. This is unlikely to have been a consistent rate and certainly the extent to which the former seabed was drowned would depend upon its slope. With a slope of about 1 in 125, each metre rise would move the shoreline about 125 m and so between 18,000 and 9500 years BP could move almost 12 km. When sealevel rose again, it flooded a land surface inherited from the sea and then attacked the areas affected by the intense weathering of the periglacial climate. However, during those periods of interglacial lower sea-level, there were shorter periods when the climate warmed and sea-level rose or was in a still-stand: for example, the Bølling/Allerød interstadial between about 14,700 to 12,700 years BP (Van Andel and Tzedakis, 1996; Adams, 2002). Wave action was potentially stable enough for cliffs to retreat several kilometres, assuming cliff retreat rates and processes were similar to today. However, given that there is some evidence that effective precipitation in Europe at 12,000 years BP was about 40% present-day values increasing from about 0.16 m/yr to 0.35 m/yr at 10,000 years BP and then more slowly to about present levels by 6000 years BP (Davis et al., 2003), failure rates in landslides and weak sands and clays would probably be lower than at present. Changes to sea-levels in the English Channel and within the sea to the south and south-east of the eastern end of the Site (Waller and Long, 2003; Paphitis et al., 2010) provide a regional context for the changes within the Site. Analysis of sea-level change within Poole Harbour (Edwards, 2001), although not part of the Site, provides a timescale within which sea-level changes would also have occurred along the open coast. By 9500 years BP, sea-level was about -45 m OD and rising at about 16 mm/yr. Between 7500 and 6000 years BP, sea-level rose at about 9 mm/yr from around -12 m OD to present-day levels (+/-5 m OD). Over the past 200,000 years, sea-level was close to present levels for less than 15% of the time, but there may be significant local variations in this

depending upon tidal patterns and crustal movements (Keen, 1995,1998). Pebble and shell fragments resting on or within strata, as well as boulders, are not necessarily representative of sea-level, but preserve the level to which beach sediments were transported on high tides and high wave events, including tsunamis. This has been investigated in detail in the Mediterranean (for example, Mottershead et al., 2014; Biolchi et al., 2015; Causon Deguara and Gauci, 2015) and demonstrates better than along the Jurassic Coast its relevance to understanding the role of high wave events. However, recent studies (Teasdale, pers. comm., September 2017) may show that the 1014 St Michael’s Day storm was the result of a tsunami event. On the Jurassic Coast (at Ringstead and north Swanage Bay), there are, and have been, beach deposits which if preserved by later sediment deposition to be exposed at some future date would not represent sea-level, but levels of higher wave events. At west Ringstead Bay cemented upper beaches have been exposed about 2 m above mean sea-level and a shingle beach raised upwards over 2.5 m on the toe of a landslide and subsequently covered by beach and landslide debris was exposed by more recent erosion. 4. Interpreting the submarine geology and geomorphology Although the present nature of the seabed provides evidence for its past development, much of its interpretation has been and remains open to debate. For example, within the World Heritage Site seabed Setting of Lyme Bay, two aspects have received most attention: (a) the evolution of Chesil Beach and (b) the relevance of the relict landslide rock arcs. Like other parts of the Jurassic Coast, the long-term origins of Chesil Beach are poorly understood and depend largely upon the chronological sequence first described by Carr and Blackley (1973) and modified by Bray (1990). The initiation and development of the beach has been outlined (May, 2003c) as follows: (i) A bank several km offshore may have existed at the same time as the emerged Portland Bill beach (Carr and Blackley, 1973), but there is no evidence in the present sea bed imagery to support this.

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

6

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

(ii) About 120,000 years BP, when sea-level fell, the level of the emerged beach, the newly exposed seabed at between 60 m and -30 m was weathered by periglacial processes. Gravel-rich deposits solifluction and fluvioglacial deposits and river gravels as well as gravels and sand derived from erosion of the coastline were spread across the floor of Lyme Bay. Today much of the rock floor of the bay is covered by sand and gravel, probably residual from that periglacial period. Degraded landslides and such solifluction-derived deposits occur up to 3 km seaward of the present coast. (iii) From about 20,000 years BP sea level rose by about 1 mm/yr and by 10,000 years BP was at about -45 m OD. The protoChesil Beach moved progressively landwards towards the earlier abandoned coastline. (iv) By about 7000–6500 years BP, sea-level was between -12 m and -4 m OD and Lyme Bay was sufficiently open to waves from the south-west for longshore sediment transport eastwards to be active in moving shingle eroded from the relict cliffs to build Chesil Beach. This process was almost certainly enhanced by the presence of a break of slope of the bedrock at about -15 m OD on which Chesil Beach built up. The large barrier beach which migrated across this part of Lyme Bay provided the seaward landscape of the Fleet, a shallow sandy gulf which flooded as sea-level rose, with marine sedimentary infill from the south-east via Portland Harbour. Coombe et al. (1998) suggest that it could have been an entirely freshwater reed swamp and through much of its existence was more like an estuary much wider than at present with extensive creek development and large intertidal low water areas. The peats below its floor at between -3.00 m and -4.32 m OD dated at between 4540  70 and 4840  70 years BP indicate its earlier presence further offshore. As a result, it is suggested that the classic model of a transgressing gravel beach should be replaced by a two-phase model in which the early Chesil Beach is a low sand and gravel barrier that provided a base upon which the more massive gravel and cobble structure was constructed as large supplies of these materials became available as the relict landslides were attacked by the rising sea. Cooper (2007), for example, suggests that the Black Ven landslide was reactivated between 5500–3000 years BP. Better understanding of the wave climate of Lyme Bay leaves questions about the effects over many centuries of major events, such as those of 13th December 1978 (a 1 in 50 event with 9 m swell) and 13th February 1979 (when 18-second period waves arrived without warning out of a moderate sea). Large storm events are a normal, if infrequent in human terms, feature of this coast and their impact on the nearshore seabed cannot be ignored. Boreholes drilled by the Central Electricity Generating Board between 1957 and 1967 revealed a wide channel down to -26 m OD between the Isle of Portland and the Weymouth Bay shore (Coombe et al., 1998), but there is no seabed evidence of a distinct south-westwards channel from the gap between Portland and Weymouth. The large anticline which existed between Upwey and Portland is drained by streams which flow into the Fleet and Weymouth Bay. There are few dated submarine features off much of the Jurassic Coast apart from offshore from the Exe estuary and the coast from Dawlish to Start Point. There is a distinct shoreline at -18 m OD along Portland’s northeastern side (Brunsden, 2012) dated at c. 8100 years BP based on the generally accepted sea-level for that time. Donovan and Stride (1961) argued that Pleistocene still-stand periods were too short for the submerged hard rock cliffs and platforms to be formed In the eastern part of Lyme Bay. However, it is possible that they are landforms re-worked as sea-levels fluctuated. Boulder arcs between 3 and 4 km offshore from Golden Cap may indicate the position of predecessors of the present cliffs

about 5000 years ago (Bray, 1990). There was probably a barrier beach well offshore which migrated onshore as sea-level rose, possibly at about the same time as the Portland raised beaches (Bray, 1992a, b) but this poses the question of the location of the barrier beach when sea-level was up to 8 m above present levels and a submerged planed-off platform, assumed to be a relic of the higher sea-level, meets the coastal slope off East Fleet at a depth of about -15 m OD (Carr and Blackley, 1973). Surveys which, for example, identify a submerged cliff line about 3 km south of the Purbeck–Needles ridge (Kellaway et al., 1975) and palaeo-landslides about 1 km from the same line indicate seabed erosion off the eastern coast of the World Heritage Site. A 2 m thick gravel ridge about 12 km south of the Needles (Velegrakis, 1994) has been tentatively interpreted as a relict barrier representing the mid-Devensian shoreline when sea-level was between 40 m and 60 m OD (ABPmer, 2012). Mottram (1972) and Jones et al. (1984) argued that the barriers to marine erosion that controlled the retreat of the Purbeck coast should be most effective where the strata dip most steeply. This suggests that the Portland–St Alban’s Head ridge which is typified by low dips (generally less than 10  to the south and south-east) would not have been easily breached. The analogous present- day landscape is between St Alban’s Head and Durlston Head, but although it has several valleys draining southwards, they do not breach the inland ridge. If it is assumed that the ridge changed in form from the Isle of Portland with its raised beach about 1 km offshore to the form east of Dancing Ledge offshore, then it probably narrowed westwards. Given the depth of the channels, the sea could have broken into the bay about the same time (about 9500 years BP) as the palaeo-valleys between Purbeck and the Needles (all shallower than -29 m OD) were flooded. If it was already breached at the time of the last high sea-level, then it might have been possible for the sea to attack the Lulworth coast. Recent palaeogeographical imagery of the seabed from 11,000 years BP to the present at 500-year intervals (Johns et al., 2015) using a Glacial Isostatic Adjustment (GIA) model and data from bathymetric surveys provides more detailed reconstructions than previously available. For example, the map for 9500 years ago indicates shallow valleys crossing Weymouth Bay which align with the valleys at Lulworth Cove, Worbarrow Bay, and Kimmeridge Bay and the valleys at Encombe and Chapman’s Pool, but such trends are difficult to confirm from the side-scan sonar and so require further investigation (Sanderson et al., 2017). Nevertheless these maps do indicate the extent to which the Portland–Purbeck ridge changed and Weymouth Bay became progressively flooded by the rising sea. The pattern of seabed relief is generally consistent with the patterns mapped by the side-scan surveys, but it also confirms the pattern associated with the sea-bed veneers that there were two areas which are associated with the locations of the incised river meanders. The question remains whether these two gaps were originally following valleys such as those in between St Alban’s Head and Durlston Head southwards or whether they were originally formed by valleys draining through the ridge northwards (the pattern between Purbeck and the Needles). Both patterns are possible. What appears most likely is that by 11,000 years BP there had been sufficient erosion of the ridge and surrounding seabed for the sea to penetrate readily into Weymouth Bay. The dated Portland Bill higher sea-level deposits are the only ones along this coast. Damon (1884) described an ‘ancient seabeach (which) over-spreads at intervals the bed of the Weymouth and Radipole Backwater’ as well as a ‘drift deposit of yellow loam’ on the side of the Preston valley which contains marine shells at ‘ten to twelve feet’ (3 m–3.7 m) above high water mark. Lower than the Portland raised beach, they are more likely to be the result of storm events. There are beaches at the mouth of Lulworth Cove and a notch in the cliffs at similar levels to the raised

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

beaches (Goudie and Brunsden, 1997), but it has not been possible to confirm a marine origin for the notch. At White Nothe and Gad Cliff, large landslides are generally described as probably stabilizing when sea- levels fell and then being re-worked as sea-level rose again. If that is accepted, then this coast must have been sufficiently open to wave action to allow landslide activity, but it ignores the subaerial processes which could maintain these landslides, even if less rapidly or frequently. Prestwich (1892) postulated that the coastline at the time of the last raised beaches was already well into Weymouth Bay suggesting the coast to the east was very close to the low submerged slope and relic landslide debris. 5. Human impacts on the site and setting The most distinctive aspect of the Holocene is that it is only when humans are available to observe their surroundings that there is any description of the processes of geology and ecology, and frequently explanation is supported by myths, limited records, etc. We can observe, describe and interpret the results of processes across geological time, but we are always interpreting on the basis of human observations extrapolated on to the observed features and so explanation of the features which are preserved in strata or landforms depends on our confidence in the precision of our understanding of the processes and their applicability to the historical evidence. Increased information about coastal zone processes during the Holocene has made it possible to analyse the interconnections between the various natural and human processes which form, maintain and change the features and characteristics of the coast. In particular, examination of the connections and flows within the Holocene coastal systems also provides tools for better understanding of how coasts develop and this can be applied to both the Holocene and previous periods. Events important for the human coastal communities and which certainly cause significant changes in the beaches (though they mostly recover) are the very large storm events as recorded in 1703, 1824, 1979 and 2013-15. Along the Jurassic Coast, the earliest human activity which affected coastal processes was the construction of harbour walls. For example, a wall was built at Lyme Regis at the end of the thirteenth century and although damaged by several storms it was not joined to the mainland until 1756. After this, the town beach was frequently lowered by storms because the longshore sediment supply from the west was reduced. At West Bay, jetties built between 1823 and 1825 had a

similar impact on the transport of shingle into Chesil Beach. More recently, seawalls and offshore breakwaters (as at Sidmouth) have modified wave and beach behaviour. Extraction of shingle for building at West Bay and Seatown during the late nineteenth and early twentieth centuries reduced beach sediment budgets (Table 4). Elsewhere, the lowering of beaches as a result of this removal for building led the British Association for the Advancement of Science (1885) and later, separately, the Royal Commission on Coast Erosion and Afforestation (1911) to examine the extent to which there was a risk of increased erosion nationally. The main emphasis at the time was on developing resorts and little thought was given to the implications of sea- wall construction (May, 2007). More recently, sea-walls and promenades at resorts including Weymouth and Swanage were designed to constrain coastal retreat. The earliest land reclamation along this coast took place in 1242–1243 when a priest is recorded as paying rent to the manor of Wyke (Johns et al., 2015). Land reclamation and port development in estuaries within the Setting, such as Poole Harbour, can be traced back to much earlier and provide archaeological evidence about sea-level changes which are not available on the open coast. All these actions have had a significant impact on this development of the coastline (May, 2007). Human activity has often made significant changes to estuarine habitats and to cross-shore flows. In Poole Harbour for example, wooden piles forming part of jetties at Cleavel Point and Green Island have been dated as constructed about 2250 years BP (LePard, 2010). There was a proposal as early as 1673–1674 to drain many of the embayments around Poole Harbour. Although nothing happened until the early eighteenth century, drainage of these areas significantly reduced the area of the estuary. The combination of the archaeological evidence and analysis of sediments within the marshlands provide much of the sea-level change data for the period from about 11,000 years ago when sea-level had reached about 40 m OD (Edwards, 2001; May and A’Court, 2010). In recent decades, there has been a growing emphasis on managing coastal and sea bed habitats with much of the coastal waters being designated as Marine Conservation Zones (MCZ). One important aspect of the Studland to Portland and the Lyme Bay to Torbay Special Areas of Conservation (SAC is their geological variety and biological diversity (Natural England, 2012). They include limestone ledges (up to 15 m across) surrounded by shelly gravel at Worbarrow Bay, shale reefs at Kimmeridge Bay and the limestone St Alban’s Ledge colonised by, for example, sponges, sea

Table 4 Human impacts. Feature

Location

Date

Action

Impact

Estuary Estuary island

Poole Harbour Green Island

Medieval Roman

Reduction in estuary area Interference with flows and shoreline sediment movement

Cliffs Cliffs and beach

Hengistbury Head Lyme Regis

Mid-19th century 16th century

Mudland reclamation Wall construction between island and mainland Extraction of ironstone boulders (‘doggers’) The Cobb

Cliffs and beach

Lyme Regis

20th century

The Cobb - joined to land

Beach

Seatown

19th century

Shingle extraction for building

Offshore gravel banks Cliff and beaches

Cliffs and beaches

Christchurch Bay

th

20

th

century th

19 -20 West Bay, Seaton, century Sidmouth, Weymouth Portland Harbour 19th century

7

Gravel extraction for beach replenishment Seawall and groyne construction

Construction of harbour breakwaters, and wharves

Accelerated cliff retreat and spit elongation Stone jetty not connected to land - longshore sediment movement continues Longshore sediment movement stopped. Down-drift increased cliff erosion. Narrowing beach increases cliff erosion and decreases longshore sediment movement

Fixed shoreline Reduced downdraft sediment supply and increased erosion. Terminal groyne problems Reduced wave action and fixed shoreline

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

8

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

fans and brittle starfish. Areas of limestone blocks form cave-like features. Off Portland, the reefs have a mixture of terrains which include rock terraces and ledges, boulder fields and cobbles. Within Lyme Bay, there are extensive reefs typically away from the coast and typified by high species richness. The Chesil Beach and Stennis Ledges MCZ extends from Abbotsbury to Weston on the Isle of Portland and offshore to include the rocky Stennis Ledges. Improved sea-bed surveys (Heeps, 1998) can support marine management in ways which allow the seabed geomorphology to provide clues to the likely seabed habitats. Surveys of the potential impact of gravel extraction (Langhorne et al., 1982) also provide information which provides potential protection to these habitats. The present state of the cliffs is recorded by the rates of retreat over the past century. Although this information provides values which can be used to judge the rate of change when sea-level was close to its present level, there was probably considerable variation from those values depending upon wave dynamics, precipitation and temperatures prevailing both at those relatively short time periods and when sea-level was significantly lower.

and shales have been eroded deeper than 30 m below present sealevel. All streams west of Weymouth would have been tributaries to at least one main river flowing into the English Channel. An alternative hypothesis is that the landscape between St Alban’s Head and Portland replicated the landscape eastwards to Durlston and that south-flowing channels were progressively eroded and deepened as the sea eroded the limestone outcrop, capturing the south side of the former Weymouth Bay drainage basin with its headwaters similarly arranged to those of the upper Corfe River. Both hypotheses require further investigation and modelling (in addressing question iv) to move towards establishing a satisfactory explanation for the evolution of the Jurassic Coast sea bed. Nevertheless the complex but important stories which derive from this sea-bed provide links between the sea bed and the coastal landscape which together provide the Setting for the World Heritage Site itself. For without those changes, the exposures which currently are the Site would not exist or continue to be revealed.

6. Conclusions

Funding

Despite the substantial sea bed imagery which is now available along the whole of the World Heritage Site questions, raised earlier, remain about the ways in which the presently submerged platforms developed and the implications of the very low angles of slope. The presence of isolated meander patterns poses questions about how they developed and the implications for the overall development of the ‘seabedscape’. Although the timing is better understood, the processes of breaching of the Portland-St Alban’s ridge and its relationship to the present-day terrestrial valleys (raised in question iv.) remain unresolved. The very open nature of Lyme Bay poses questions about the destruction of a former coast west from Portland Bill and the formation and resilience of the boulder beaches, etc, which evolved to the present strongly wave-aligned Chesil barrier beach. The rock platforms which form much of the floor of Weymouth Bay are comparable to planation surfaces which are observed today, although at higher levels, in limestone landscapes such as the south coast of the Gower Peninsula in South Wales. The combined processes over thousands of years of marine erosion and periglacial weathering have produced platforms which expose very well the structural patterns of the anticline and associated faults of the World Heritage Site’s Setting. The hypothesis for the evolution of the submarine setting of the Jurassic Coast in Weymouth Bay needs to consider the possibility that, just as Poole and Christchurch bays resulted from the erosion of north-flowing valleys within the region south of the Needles– Purbeck ridge, there was at least one north-flowing valley which cut through the Portland–St Alban’s Head ridge to join the streams draining the eastern and northern slopes of Weymouth Bay and then flowing westwards north of Portland into Lyme Bay. The available sea-bed imagery for the past 10,000 years indicates that not only did the sea not enter Weymouth Bay from Lyme Bay, but that Weymouth Bay was flooded progressively from the south. However, not only was Lyme Bay progressively flooded but also the anticline between Portland and Upwey was removed. In answer to question iii, the presence of the rock meanders is indicative of streams flowing southwards and their incision, in common with other comparable features (Ambert, 2013), could have arisen from a combination of increased flows resulting from a steepening of the thalweg as sealevel fell and/or increased flows as results of drainage from lagoons such as that behind St Alban’s Ledge or a large lagoon for which there is map evidence north of the Adamant Shoal. This does not, however, take account of Brunsden’s view (pers. comm., 2016) that the incised rock channels were draining a significant lagoon which had formed immediately west of St Alban’s Head where the Kimmeridge clays

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Acknowledgements The reviewers of this paper provided critical and constructive comments for which the author is very grateful. References ABPmer, 2012. Navitus Bay Wind Park: Physical Processes Assessment. . Adams, J., 2002. Europe during the last 150,000 years Accessible at. . http://www. esd.ornl.gov/projects/qen/nercEUROPE.html. Ambert, M., 2013. The Cirque de Navacelles: a major Geomorphosite in the Grands Causses Karstic Region. In: Fort, M., Andre, M.-F. (Eds.), Landscapes and landforms of France. Springer, pp. 105–114. Antoine, P., Coutard, J.-P., Gibbard, P., Hallegouet, B., Lautridou, J.-P., Ozouf, J.-C., 2003. The Pleistocene rivers of the English Channel region. Journal of Quaternary Science 18, 227–243. Badman, T.D., Gravelle, M.A., Davis, G.M., 1999. Seabed imaging using a computermapping package: an example from Dorset. Quarterly Journal of Engineering Geology and Hydrogeology 33, 171–175. Bastos, A., Collins, M., Kenyon, N., 2003a. Water and sediment movement around a coastal headland: Portland Bill. Ocean Dynamics, southern U.K.53, pp. 309–321. Bastos, A., Collins, M., Kenyon, N., 2003b. Morphology and internal structure of sand shoals and sandbanks off the Dorset coast, English Channel. Sedimentology 50, 1105–1122. Biolchi, S., Furlani, S., Antonioli, F., Baldassini, N., Cucchi, F., Deguara, J., Devoto, S., Di Stefano, A., Evans, J., Gambin, T., Gauci, R., Mastronuzzi, G.A., Monaco, C., Scicchitano, G., 2015. Extreme waves impact on Malta (Mediterranean Sea). In: Galea, P., Borg, R.P., Farrugia, D., Agius, M.R., D’Amico, S., Torpiano, A., Bonelli, M. (Eds.), Proceedings of the International Conference: Geo-Risks in the Mediterranean and their Mitigation, , pp. 83–90. Bray, M.J., 1990. Landslides and coastal zone sediment transport. In: Allison, R.J. (Ed.), Landslides of the Dorset Coast, British Geomorphological Research Group, Field Guide, , pp. 107–117. Bray, M.J., 1992a. Coastal Sediment Supply and Transport. In: Allison, R.J. (Ed.), The Coastal Landforms of West Dorset, Geologists’ Association, Field Guide No. 47, , pp. 94–105. Bray, M.J., 1992b. Chesil Beach. In: Allison, R.J. (Ed.), The Coastal Landforms of West Dorset, Geologists’ Association, Field Guide No. 47, , pp. 106–118. British Association for the Advancement of Science, 1885. Report of the Committee appointed for the purpose of inquiring into the Rate of Erosion of the Sea-coasts of England and Wales, and the Influence of the Artificial Abstraction Of Shingle or other Material in that Action. . Brunsden, D., 2012. The Geo-marine resources of the South Dorset Coast Marine Natural Area Accessible at. . http://www.cscope.eu/_files/results/activity_1/ dorset/Appendices/Appendix%206.%20Areas%20of%20Geological% 20Interest.pdf. Carr, A.P., Blackley, M.W.L., 1973. Investigations bearing on the age and development of Chesil Beach, Dorset, and the associated area. Transactions of the Institute of British Geographers 58, 99–111. Causon Deguara, J., Gauci, R., 2015. Evidence of extreme wave events from boulder deposits on the south-east coast of Malta: storm or tsunami? In: Galea, P., Borg,

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx R.P., Farrugia, D., Agius, M.R., D’Amico, S., Torpiano, A., Bonello, M. (Eds.), Proceedings of the International Conference: Geo-Risks in the Mediterranean and their mitigation, , pp. 94–97. Coombe, E.D.K., Bruce, A.S., Goudie, A.S., Juggins, S., Parker, A.G., Whittaker, J.E., 1998. The evolution of the Fleet Lagoon, Dorset, southern England, during the last c. 6000 years: preliminary evidence from a multidisciplinary study. . Cooper, R.G., 2007. Mass Movements in Great Britain, Geological Conservation Review Series, No.33. Joint Nature Conservation Committee, Peterborough, pp. 348pp. Damon, R., 1884. Geology of Weymouth, Portland and coast of Dorset-shire, from Swanage to Bridport-on-the-Sea, with natural history and archaeological notes. Weymouth, R.F. Damon. Darton, D.M., Dingwall, R.G., McCann, D.M., 1981. Geological and Geophysical investigations in Lyme Bay, IGS Report No.79/10. . Davies, K.H., Keen, D.H., 1985. The age of the Pleistocene marine deposits at Portland, Dorset. Proceedings of the Geologists’ Association 96, 217–225. Davis, B.A.S., Brewer, S., Stephenson, A.C., Guiot, J., 2003. The temperature of Europe during the Holocene reconstructed from pollen data. Quaternary Science Reviews 22, 1701–1716. Design, L.D.A., 2008. Dorset coast land and seascape character assessment. Accessible at http://www.dorsetforyou.com/media.jsp? mediaid=155749&filetype=pdf and http://www.dorsetforyou.com/media.jsp? mediaid=155131&filetype=pdf Section 4. . Donovan, D.T., Stride, A.H., 1961. An acoustic survey of the sea floor south of Dorset and its geological interpretation, Philosophical Transactions of the Royal Society of London B244. , pp. 299–330. Dorset Wildlife Trust, 2010. DORIS map. Accessible at http://www. dorsetwildlifetrust.org.uk/doris_map or http://doris.s3.amazonaws.com/files/ DORISGE/DORISfull.html or https://www.dorsetforyou.gov.uk/ . . . /13. _DORset_Integrated_Seabed_survey_(DORIS). . Drayson, A., 2005. An investigation into the shallow seabed geomorphology of North Weymouth Bay using acoustic techniques. Unpublished PhD Thesis. Bournemouth University. Durrance, E.M., 1969. The Buried Channels of the Exe. Geological Magazine 106, 174–189. Edwards, R.J., 2001. Mid- to late Holocene relative sea-level change in Poole Harbour, southern England. Journal of Quaternary Science 16, 221–235. England, Natural, 2012. Studland to Portland SAC Selection Document Accessible at. . http://www.naturalengland.org.uk/images/S2P_SAD_tcm6-33696.pdf. Forster, G.R., 1961. An underwater survey on the Lulworth Banks. Journal of the Marine Biological Association of the United Kingdom 41, 157–160. Gallois, R.W., 2011. A fossil landslide preserved offshore at Lyme Regis, 12. Geoscience in South-West England, Dorset, U.K, pp. 329–334. Goudie, A., Brunsden, D., 1997. Classic landforms of the East Dorset Coast. The Geographical Association, Sheffield, pp. 48pp. Heeps, C., 1986. Sediment Circulation in Mixed Gravel and Shingle Bayhead Beaches on the South East Dorset Coast, U.K.. Unpublished PhD Thesis. Council for National Academic Awards (CNAA). Heeps, C., 1987. Recognition and prediction of seabed sediment patterns, M.O.D. Report No.2222/01/ARE(P). . Heeps, C., 1998. Seabed Geomorphology and Shallow Marine Boulder Fields. The Application of Side-Scan Sonar to Coastal Geomorphological Study and Marine Resource Management, Fourth Underwater Science Symposium, Collected papers., Dorset. Johns, C., Kirkham, G., Cousins, T., Parham, D., 2015. Rapid coastal zone assessment survey: Phase one Desk-based Assessment for South-West England (South Coast Dorset) 6673. Report No. 2014R043. Accessible at https://content. historicengland.org.uk/images-books/publications/rczas-phase-one-deskbased-assess-sw-england-south-coast-dorset/6673-dorset-rczas- report.pdf/. . Jones, M.E., Allison, R.J., Gilligan, J., 1984. On the relationship between geology and coastal landform in central southern England. Proceedings of the Dorset Natural History and Archaeological Society 18, 174–184. Keen, D.H., 1995. Raised Beaches and Sea-Levels in the English Channel in the Middle and Late Pleistocene: Problems of interpretation and implications for the isolation of the British Isles. In: Preece, R.C. (Ed.), Island Britain: A Quaternary Perspective, Geological Society, 96. Special Publications, London, pp. 63–74. Keen, D.H., 1998. The Quaternary History of the Dorset, South Devon and Cornish Coasts. In: Campbell, S., Scourse, J.D., Hunt, C.O., Keen, D.H., Stephens, N. (Eds.), Quaternary of South-West England, Geological Conservation Review Publication No 14. Joint Nature Conservation Committee, Peterborough, pp. 157–169. Kelland, N.C., 1975. Submarine Geology of Start Bay determined by Continuous Seismic Profiling and Core Sampling. Journal of the Geological Society, London 131, 7–17. Kellaway, G.A., Redding, J.H., Shepard-Thorn, E.R., Destomes, J.-P., 1975. The Quaternary history of the English Channel, Philosophical Transactions of the Royal Society A279. , pp. 189–218. Langhorne, D.N., Heathershaw, A.D., Read, A.A., 1982. The mobility of sea- bed gravel in the West Solent. A report on site selection, seabed morphology and sediment characteristics. Report No. 140, Institute of Oceanographic Sciences Accessible at. . http://nora.nerc.ac.uk/114560/1/14560-01.pdf. LePard, G., 2010. Boundaries, Quays, Jetties, Slipways & Marinas. In: Dyer, B., Darvill, T. (Eds.), The Book of Poole Harbour. The Dovecote Press Ltd, Wimborne, pp. 35–48. Long, A.J., Tooley, M.J., 1995. Holocene Sea-Level and Crustal Movements in Hampshire and Southeast England, United Kingdom. Journal of Coastal

9

Research, Special Issue No 17, Holocene Cycles: Climate, Sea-Levels, and Sedimentation 299–310. May, V.J., 2003a. Ballard Down, Dorset. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough, pp. 176–181. May, V.J., 2003b. Budleigh Salterton Beach, Devon. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough, pp. 251–254. May, V.J., 2003c. Chesil Beach, Dorset. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough, pp. 254–266. May, V.J., 2003d. Ladram Bay, Devon. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough, pp. 138–141. May, V.J., 2003e. Lyme Regis to Golden Cap, Dorset. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough, pp. 151–157. May, V.J., 2003f. The Dorset Coast: Furzy Cliff to Peveril Point. In: May, V.J., Hansom, J.D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No. 28. Joint Nature Conservation Committee, Peterborough, pp. 624–642. May, V., 2007. Sustainable management of a high value high risk coast: the role and effectiveness of technological interventions. In: Smith, J.M. (Ed.), Coastal Engineering, , pp. 1925–1937 2006. May, V., 2008a. Geomorphology of Dorset: a review. Proceedings of the Dorset Natural History and Archaeological Society 129, 149–162. May, V., 2008b. Integrating the geomorphological environment, cultural heritage, tourism and coastal hazards in practice. Geografia Fisica e Dinamica Quaternaria 31, 187–194. May, V., 2013. Dorset’s submarine geomorphology. Proceedings of the Dorset Natural History and Archaeological Society 134, 84–98. May, V., 2014. Coastal cliff conservation and management: the Dorset and East Devon Coast World Heritage SiteJournal of Coastal Conservation 19, 821–829. . Accessible at http://link.springer.com/article/10.1007/s11852-014-0338-8. May, V., A’Court, M., 2010. The formation of the Harbour. In: Dyer, B., Darvill, T. (Eds.), The Book of Poole Harbour. The Dovecote Press Ltd., Wimborne, pp. 17–21. May, V.J., Ellis, N.V., 2003. Legal protection of the GCR sites. In: May, V.J., Hansom, J. D. (Eds.), Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No. 28. Joint Nature Conservation Committee, Peterborough, pp. 28–30. May, V.J., Hansom, J.D. (Eds.), 2003. Coastal Geomorphology of Great Britain, Geological Conservation Review Series, No.28. Joint Nature Conservation Committee, Peterborough 737 pp. McCann, D.M., Culshaw, M.G., 2001. Discussion of ‘Seabed imaging using a computer-mapping package: an example from Dorset by T.D. Badman, M.A. Gravelle, and G.M.Davis. Quarterly Journal of Engineering Geology and Hydrogeology 33, 171–175. Mottershead, D.N., Bray, M., Soar, P., Farres, P., 2014. Extreme wave events in the central Mediterranean: Geomorphic evidence of tsunami on the Maltese Islands. Zeitschrift für Geomorphologie 58 (3), 385–411. Mottram, B., 1972. Some aspects of the evolution of parts of the Dorset coast. Proceedings of the Dorset Natural History and Archaeological Society 94, 21–26. Nunny, R.S., 1995. Lyme Bay Environmental Study, Vol. 1 Hydrography, Vol. 2 Sediments. Project Report by Ambios Environmental Consultants Ltd. for Kerr McGee Oil (UK) plc. Paphitis, D., Bastos, A.C., Evans, G., Collins, M.B., 2010. The English Channel (La Manche): evolution, oceanography and sediment dynamics – a synthesis. In: Whitaker, J.E., Hart, M.B. (Eds.), Micropalaeontology, sedimentary environments and stratigraphy: a tribute to Dennis Curry (1912–2001), The Micropalaeontological Society. Special Publication, pp. 99–132. Pingree, R.D., 1978. The formation of the Shambles and other banks by tidal stirring of the seas. Journal of the Marine Biological Association of the United Kingdom 58, 211–226. Prestwich, J., 1892. The Raised Beaches, and ‘Head’ or Rubble-drift, of the South of England: their Relation to the Valley Drifts and to the Glacial Period; and on a late post-Glacial Submergence. Quarterly Journal of the Geological Society, London 48, 263–343. Rohling, E.J., Grant, K., Hemleben, C.H., Siddall, M., Hoogakker, B.A.A., Bolshaw, M., Kucera, M., 2008. High rates of sea-level rise during the last interglacial period. Nature Geoscience 11, 38–42. Royal Commission on Coast Erosion and Afforestation, 1911. Third (and Final) Report of the Royal Commission Appointed to inquire into and to report on certain Questions affecting Coast Erosion, the Reclamation of Tidal Lands, and Afforestation in the United Kingdom. . Sanderson, D.J., Dix, J.K., Westhead, R.K., Collier, J.S., 2017. Bathymetric mapping of the coastal and offshore geology and structure of the Jurassic Coast, Weymouth bay, UK. Journal of the Geological Society, London doi:http://dx.doi.org/ 10.1144/jgs2016-070. Van Andel, T.H., Tzedakis, P.C., 1996. Palaeolithic landscapes of Europe and environs: 150,000-25,000 years ago: an overview. Quaternary Science Reviews 15, 481–500. Vaslet, D., Larsonneur, C., Auffret, J.P., 1979. Carte des sédiments superficiels de la Manche - Map of the superficial sediments of the English Channel. 1:500000. Bureau de Recherches Géologiques et Minières, Orleans.

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003

G Model PGEOLA 759 No. of Pages 10

10

V.J. May / Proceedings of the Geologists’ Association xxx (2019) xxx–xxx

Velegrakis, A.F., 1994. Aspects of the morphology and sedimentology of a transgressional embayment system: Poole and Christchurch Bay, Southern England. Unpublished PhD Thesis. University of Southampton. Velegrakis, A.F., Dix, J.K., Collins, M., 1999. Late Quaternary evolution of the upper reaches of the Solent River, Southern England, based upon marine geophysical evidence. Journal of the Geological Society, London 156, 73–87. Waller, M.P., Long, A.J., 2003. Holocene coastal evolution and sea-level change on the southern coast of England: a review. Journal of Quaternary Science 18, 351–359.

Westhead, K., Smith, K., Campbell, E., Colenutt, A., McVey, S., 2015. Pushing the boundaries: Integration of multi-source digital elevation model data for seamless geological mapping of the UK’s coastal zone. Earth and Environmental Science Transactions of the Royal Society of Edinburgh 105, 263–271. Westhead, R.K., Sanderson, D.J., Dix, J.K., 2017. Bedrock map for the off-shore Weymouth Bay area, with seamless coastal joint to BGS onshore (BGS Geology 10k) mapping. Bedrock Geology. 1:10 000 (Marine Environmental Mapping Programme, MAREMAP), .

Please cite this article in press as: V.J. May, The submarine landscape of the ‘Jurassic Coast’ World Heritage Site, Dorset, UK and its Setting, Proc. Geol. Assoc. (2019), https://doi.org/10.1016/j.pgeola.2019.04.003