Late-Holocene (post-4000 years BP) coastal dune development in. Northumberland, northeast England. Peter Wilson,1 Julian D. Orford,2 Jasper Knight,1.
The Holocene 11,2 (2001) pp. 215–229
Late-Holocene (post-4000 years BP) coastal dune development in Northumberland, northeast England Peter Wilson,1 Julian D. Orford, 2 Jasper Knight,1 Sharon M. Braley1 and Ann G. Wintle3 (1School of Environmental Studies, University of Ulster at Coleraine, Cromore Road, Coleraine, Co. Londonderry BT52 1SA, Northern Ireland, UK; 2School of Geography, Queen’s University of Belfast, Belfast BT7 1NN, Northern Ireland, UK; 3Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Dyfed SY23 3DB, Wales, UK) Received 20 January 2000; revised manuscript accepted 15 May 2000
Abstract: The recent environmental history of coastal dune systems in Northumberland, northeast England, has been examined using geomorphological, stratigraphical and sedimentological techniques linked to radiocarbon and infrared-stimulated luminescence (IRSL) dating. Stratigraphies were determined from 22 vibracores and three sections, and dune chronology was based on 28 14C dates, from peat and soil organic horizons, and 26 IRSL dates on K-feldspar grains from within sand layers. Almost all dune systems are associated with regressive shorelines consequent upon a fall in relative sea level (RSL) from its Holocene peak, and indicate RSL functioned as a macroscale control on dune development. Where dunes are anchored on terrestrial sediment, dune expansion may have been either transgressive or regressive in nature. Where near-shore marine sediments form the dune substrate, a regressive (prograding) dune model seems most likely. Most dune building occurred during the ‘Little Ice Age’ (LIA), probably in association with specific climatic and morphosedimentary conditions, principally periods of easterly circulation, a greater frequency of severe North Sea storms, RSL fall, and sediment and accommodation space availability. Dune development in Holocene cool intervals earlier than the LIA was of limited spatial extent, suggesting some differences in prevailing conditions at those times. Key words: Coastal sand dunes, radiocarbon dating, IRSL dating, relative sea-level change, climatic change, ‘Little Ice Age’, late Holocene, Northumberland.
Introduction Sand dunes of late-Holocene age are important morphological elements along the Atlantic coasts of northwestern Europe and have been the focus of much recent research aimed at explaining their development, age structure and function within the context of coastal-zone dynamics (e.g., Bressolier et al., 1990; Wilson, 1990; Granja and de Carvalho, 1992; Carter and Wilson, 1993; Ritchie and Whittington, 1994; Selsing and Mejdahl, 1994; Devoy et al., 1996; Wilson and Braley, 1997; Gilbertson et al., 1999). Detailed dune studies have also been undertaken at sites around semi-enclosed seas (Baltic, North and Mediterranean) of Europe (e.g., Martin, 1988; Boro´wka, 1990a; 1990b; Christiansen et al., 1990; Klijn, 1990a; Tsoar, 1990; Sanjaume and Pardo, 1992; Clemmensen et al., 1996). As a result, a valuable body of information relating dunes, from numerous diverse situations, to both Arnold 2001
local and regional environmental changes (i.e., climatic, sea-level and/or human-induced changes) at the land-sea interface is now available. One reason for the recent proliferation in the volume of coastal dune research stems from an awareness that global warming, and predicted relative sea-level (RSL) rise and/or increased storminess, will have a greater impact on ‘soft’ rather than ‘hard’ coasts, although the nature and magnitude of that impact remains difficult to quantify (van der Meulen, 1990; Carter, 1991). As coastal dunes are considered to be relatively fragile systems currently providing protection to many low-lying areas, there is a need to understand the Holocene evolution of dunes in relation to established patterns of environmental change. Only then will it be possible to evaluate and model the likely response of dunes to future change. In contrast to the abundance of dune studies undertaken elsewhere in Europe, the dune systems along the Irish Sea and North 0959-6836(01)HL458RP
216 The Holocene 11 (2001)
Sea coasts of Great Britain have not generated a similar level of research activity. Only for the Sefton coast of northwest England (Pye, 1990; Atkinson and Houston, 1993; Pye and Neal, 1993) and east coast of Scotland (Robertson-Rintoul and Ritchie, 1990; Ross, 1992) have dunes been subjected to detailed investigation. Little is known about the numerous dune systems along the east (North Sea) coast of England, and the Irish Sea coasts of Wales and southwest Scotland. As part of the Natural Environment Research Council (NERC) funded Land-Ocean Interaction Study (LOIS) the coastal dune systems of Northumberland and Norfolk, eastern England, have been examined with the aim of reconstructing their environmental history through geomorphological, stratigraphical and sedimentological investigations linked to 14C and luminescence dating. The work forms part of the Land-Ocean Evolution Perspective Study (LOEPS), one of the interconnected components of the LOIS programme. Only dune development in Northumberland is discussed in this paper, details of dune evolution in Norfolk are reported elsewhere (Knight et al., 1998; Orford et al., 2000).
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Holy Island
North Farne Islands
Ross Links Bamburgh St. Aidan’s Dunes Seahouses Newton Links
Central
Beadnell Bay
Embleton Bay
Embleton
Characteristics of the Northumberland coast
Dune systems Boulmer
Locations of cores Exposures sampled
Alnmouth
Alnmouth Bay
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Druridge Bay
Cresswell 0
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Figure 1 Locations of coastal dune systems in Northumberland, coring sites and exposures sampled.
m OD
The coast of Northumberland between Cresswell in the south and Cheswick in the north (Figure 1) is relatively low lying (⬍30 m OD) and consists of several sand- or mud-dominated bays, river estuaries and bedrock headlands. Along this 93 km coastline (including Holy Island) dune systems occupy c. 45 km of shoreline and cover 1374 ha (Radley, 1992). Bedrock outcrops controlling coastal deposition are of Carboniferous limestones, sandstones, shales and Coal Measures, and the intrusive PermoCarboniferous quartz-dolerite Whin Sill (Johnson, 1995). In many places coastal bedrock is masked by complex sequences and various thicknesses of glacial drift, deposited in the Dimlington Stadial (26 000–13 000 14C years BP) of the late Devensian (Lunn, 1995); and/or estuarine and intertidal muds (Plater and Shennan, 1992); salt-marsh, freshwater and terrestrial peats (Raistrick and Blackburn, 1932; Frank, 1982; Innes and Frank, 1988; Plater and Shennan, 1992); and gravel beach ridges (Carruthers et al., 1927; Steers, 1969; Galliers, 1970), all of which are associated with Holocene coastal evolution. The dunes have developed across this variety of substrates. Evidence for Holocene RSL change from study of intercalated sequences of marine and terrestrial sediments was presented by Plater and Shennan (1992) for the northern and central sectors of the Northumberland coast. They showed that RSL changed by only c. 2.6 m during the last 8000 years, and noted that this represented a substantially smaller amount than for many other coastal areas of Great Britain. However, the morphological setting of the Northumberland locations investigated suggested that the regional signal of RSL may have been suppressed by more sitespecific factors. Recent work by Shennan et al. (2000) has demonstrated RSL to have a more complex history than previously envisaged. RSL curves for northern, central and southern sectors of the Northumberland coast have been established and indicate that RSL changed by 4–7 m over the last 9000–10 000 years (Figure 2). The rising limb of each curve is well constrained by a number of dated index points, but for the last 3000 years index points are lacking in all three coastal sectors and the rate and style of RSL fall from Holocene peak to present-day mean sea level is inferred. The disparities in elevations attained and in magnitude of RSL change between these regions are attributed by Shennan et al. (2000) to differential crustal movements. At only one location has the timing of dune development been determined previously. An exposure at the northern end of Druridge Bay (Figure 1) was described by Frank (1982) and Innes and
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Figure 2 Relative sea-level curves for sectors of the Northumberland coast (after Shennan et al., 2000).
Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 217
Frank (1988) with 14C dates reported from both marine shells within the dunes, and from an underlying peat bed. Peat accumulation began c. 4900–4700 14C years BP and was attributed to waterlogging, landward of a coastal sand barrier, in association with RSL rise. Termination of peat growth, caused by the deposition of dune sands, occurred at c. 2800 14C years BP. A lag deposit of marine shells within the dunes returned a 14C age estimate of c. 1000 years BP and was interpreted to represent a hiatus in dune development. Archaeological materials recovered from the intertidal zone, the dunes and coastal hinterland, demonstrate a human presence in the area since the early Mesolithic, c. 7000 years BC (Anon, no date; O’Sullivan and Young, 1995). From pollen analysis of the Druridge Bay peat, Innes and Frank (1988) identified phases of woodland clearance and agricultural activity in the mid- and late Bronze Age, c. 1700–500 years bc, and suggested that such practices could have resulted in erosion of the lighter soils of the dunefringe area. At present the coast is marginally macrotidal with a mean spring tidal range of 4.1–4.2 m (Plater and Shennan, 1992). The wind regime at Boulmer (Figure 1) is dominated by winds with speeds in the range 0.3–5.4 m s−1 (58.7%) and 5.5–10.7 m s−1 (36.7%). Onshore winds only occur for 20.8% of the time and offshore-directed westerly components for 48.5% of the time (Table 1).
granulometer was used to obtain grain-size spectra between 10 and 1200 m over intervals of 4 m. Data were converted to the phi (ø) scale and grouped at 0.25 intervals. Sand in the size range 1200–2000 m was dry-sieved at 0.25ø intervals. Textural parameters were determined using graphical measures. Percentage loss in sample weight following treatment with an excess of dilute hydrochloric acid was used as an estimate of CaCO3 content. Pollen analysis was conducted on mud recovered from beneath the dunes at Newton Links (Figure 1). The chronological framework for dunefield development was established through 23 AMS and five conventional 14C dates derived from soil organic matter and peat, and 26 infrared stimulated luminescence (IRSL) dates on K-feldspar grains from within sand layers. Thicknesses of materials selected for 14C dating ranged from 1 to 11 cm depending on the sample thicknesses available and their organic content as determined by loss-onignition at 430°C. Samples for AMS dating were measured at the University of Arizona following sample preparation at the NERC Radiocarbon Laboratory, East Kilbride; samples for conventional dating were measured at the NERC Laboratory (one sample) and Beta Analytic, Miami (four samples). Ages were calibrated to calendar years BP using method A (intercepts) of the CALIB 4.1 program (Stuiver and Reimer, 1993). Samples for IRSL dating, representing core lengths of 10–20 cm, were removed under red light and processed following the methods outlined in Wintle et al. (1998). In particular, K-rich feldspar grains of 180–210 m were obtained using heavy liquid separation. Eighteen determinations of equivalent dose were made on each sample using the single-aliquot additive-dose procedure of Duller (1991). Beta counting was used to determine both the bulk beta dose rate and the K content of the separated feldspars. Thick source alpha counting was used to determine the alpha activity and the uranium and thorium content. The cosmic dose rate was calculated using the measured depth below the surface. A time averaged water content of 5% was assumed for all samples, except for HI2/4 for which 20% was assumed, on the basis of its current water content and its location between two peat layers.
Methodology Dunefield morphology was assessed by examination and interpretation of aerial photographs at a scale of 1:10 000 followed by field mapping and surveying using a Trimble 4400 global positioning system (GPS) at selected locations. Stratigraphical and sedimentological investigations were based on inspection and sampling of two natural exposures (ALN2 and AB2), from which three sections were logged, and 22 cores, from within the dunefields, obtained by low-disturbance vibracoring undertaken by the British Geological Survey (Figure 1). Coring depths ranged from 1.5 to 9 m; total length of cores was 108 m. At 13 sites cores penetrated the dune substrate (sand and gravel, glacial drift, mud or peat) for depths of up to 1.2 m; at nine sites the dune base was not reached. Cores were taken in 1 m lengths (runs) of 6 cm diameter plastic liner. Some runs contained less than 1 m of dune sediment because of sand compaction and/or leakage from the liner during extraction; dune sediment recovery per run varied between 20 and 95% of the run length with a mean of 61% (n = 99). Ground surface elevation (m OD) at each core location was determined using a Sokkia total station surveying instrument. Core runs were split vertically under a red light source in the laboratories of the British Geological Survey, Keyworth. One half of each run was stored in darkness for subsequent sampling for luminescence dating; the other half was photographed, logged stratigraphically and, where present, organic materials removed for 14C dating. Selected runs from three cores (from Ross Links, Newton Links and Druridge Bay) were sampled at 0.5 cm intervals for grain size and/or CaCO3 determination. A Galai CIS laser
The coastal dunes Physical setting and morphology Coastal dunes in Northumberland occur as confined sediment-systems located where geological structure and site-specific geomorphological factors (e.g., coastal configuration, accommodation space, sediment availability) have exercised significant control on sand accumulation. Four broad types of physical setting for dune development have been recognized on this coast, namely driftcovered bedrock island, embayments/estuary mouths, open coast progradational zones, and headlands. Examples of these settings and their dune systems are outlined below. Except where otherwise stated, all the contemporary dunes are predominantly fixed, i.e., they are well vegetated and stable. Holy Island is the largest of over 12 islands off the Northumberland coast and the only one on which substantial dune development has occurred. It has previously been considered that present
Table 1 Percentage frequencies of wind speeds and direction for Boulmer (source: Monthly Weather Report (Annual Summaries 1980–91), Meteorological Office) Speed (m s−1)
Direction
⬎17.2
10.8–17.1
5.5–10.7
0.3–5.4
0
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NE
E
SE
S
SW
W
NW
0.1%
3.9%
36.7%
58.7%
0.6%
11.9%
5.8%
6.4%
8.6%
18.2%
14.5%
23.4%
10.6%
218 The Holocene 11 (2001)
morphology of the island resulted from gravel beaches linking several separate drift-covered bedrock isles (Carruthers et al., 1927; Steers, 1969; Robson, 1982). The island (4.7 km east–west) encloses the intertidal Holy Island Sands and Fenham Flats (muds) to the south; at low tide Goswick Sands (0.5–2.0 km wide) connect the western end of the island with the coast at Cheswick (Figure 1). Dunes occupy the northern area (The Links) of the main part of the island (Figure 3A) where they are underlain by drift-covered bedrock that dips to the south; although dune crests reach 24 m OD in this area, sand thicknesses are somewhat less because of the initial elevation provided by bedrock and drift. Across Snook Neck and The Snook, dunes are anchored on gravel ridges (2–4 m OD); many dunes rise to 8–15 m OD in these areas (Figure 4A). Across much of The Snook, dunes occur as irregularshaped mounds, many of which may be erosional remnants of formerly more extensive ridges. Shore-parallel dune ridges (⬍650 m long) are present along the north side of the island and shoreoblique ridges (100–200 m long) are found in the southern part of The Snook and The Links. Numerous deep, circular to elliptical depressions are common within the dunes of The Snook; they are vegetated and interpreted as former blowouts. Several discrete embayments bounded by drift or bedrock cliffs and containing dunes occur along the Northumberland coast. Such dune systems range in shoreline length from 9 km at Druridge Bay to c. 500 m at Boulmer (Figure 1). Some embayments possess estuary exits for small fluvial catchments and the beach and dune systems provide protection, from marine erosion, to muds and organic accumulations that occur inland of the dunes (e.g., at Beadnell Bay and Alnmouth). Dune system morphology at Druridge Bay consists of discontinuous shore-parallel ridges (Figure 3B) of which the seawardmost (outer) ridge is always the highest (10–16 m OD; Figure 4B). Lower inland ridges, some of which are wider than the outer ridge, occur along much of the bay. Several deep blowouts, open to the east, are present in the outer ridge; their lack of vegetation and presence of sparsely vegetated blowover plumes indicate that sand continues to be reworked landwards under conditions of easterly air flow. The maximum width of the Druridge Bay dune system is 300 m but along much of the bay it does not exceed a width of 150 m. The Beadnell Bay (Newton Links) dune system (Figure 1) is of smaller areal extent than that at Druridge Bay, extending alongshore for 3 km and attaining a maximum width of 350 m. An additional distinguishing characteristic is the estuary at the centre of the bay (Figure 3C) near to which dune progradation is evident. North of the estuary the system is dominated by a single, shoreparallel dune ridge rising 10–15 m above the beach and with marked scarping on its seaward side. Several blowouts (both active and inactive), open to the east, breach the ridge towards its northern end. Landward of the ridge the dunes are low (⬍3 m amplitude), hummocky and lack clearly defined linear elements. South of the estuary for a distance of c. 750 m several dune ridges are aligned parallel or subparallel to the shoreline. The dunes reach their maximum width in this area. The surveyed profile through core position NL2 (Figures 3C and 4C) shows a high (14 m OD) landward ridge fronted by a series of ridges not exceeding 10 m OD; these lower ridges converge northwards into the estuary. In contrast to the landward ridge the lower ridges are dominated by Ammophila arenaria (marram grass) with few herbaceous species present. Taken together, these characteristics indicate the lower ridges probably result from more recent and marked dune progradation. Further south the dune system narrows and the number of ridges present declines; from thereon the remainder of the system is characterized by a single high ridge at the shoreline backed by low and hummocky dunes. Open coast prograded dune systems occur at Cheswick and Ross Links (Figure 1). The Cheswick system is dominated by two ridges 30–200 m apart and of similar height (10–20 m OD). In
places subsidiary ridges, not exceeding 8 m OD, occur seaward of and between the two ridges. Ross Links (Figures 1 and 3D) is part of a 3 km wide foreland that extends seaward for 2 km between Fenham Flats and Budle Bay. The dune island of Old Law forms a northern extension to the foreland. Most of the foreland is below 10 m OD. In the western half of the sandy area shown in Figure 3D the ground surface undulates gently and aeolian sand thicknesses are usually less than 2 m; podzolized glacifluvial sediments underlie the sands and are exposed in shallow blowouts. North of the surveyed profile (Figure 3D) prominent shore-parallel dune ridges are restricted to a zone 200 m in width along the outer coast, with the highest dunes (14–16 m OD) marking the landward limit of this zone (Figure 4D). To seaward, ridges possess a more open vegetation dominated by A. arenaria, do not rise above 8 m OD, and have amplitudes of 1–4 m. In the southern part of the system dune ridges are both more numerous and continuous within a 300 m wide zone. Several ridges converge southwards to near the southeastern curve of the shoreline; ridge-crest elevations are generally within the range 6–9 m OD. Some of these ridges have developed within the last 50–60 years, judging from the current position of a Second World War defensive structure. The purpose of this structure indicates it was probably built closer to the shoreline than it now is and commanded a view of the beach. Dunes associated with headlands are found between Amble and Hauxley, and Bamburgh and Seahouses (St Aidan’s dunes) (Figure 1). At each location headlands have provided a situation facilitating dune development and protecting from subsequent erosion. Headland dune systems extend alongshore for up to 4.5 km but rarely exceed 350 m in width. At Amble the dune system consists of a single ridge (10–12 m OD) at the shoreline landward of which is low amplitude (⬍2 m) and hummocky dune topography at slightly lower elevation (6–8 m OD). The morphology of the St Aidan’s dunes displays marked variation alongshore. In the south the system is c. 180 m wide and consists of a 7 m high ridge at the shoreline landward of which is a higher (11 m OD) and wider ridge. The central part of the system is c. 90 m wide and dominated by a single broad ridge with crest elevation at 9.5 m OD; low amplitude (⬍2 m) ridges at 6–7 m OD occur on the landward side of the system. At its northern end the dune system is c. 380 m wide and possesses two ridges of similar height (13– 14 m OD) c. 220 m apart. Between these ridges are several lower ridges at 5–10 m OD. Stratigraphy and facies Lithostratigraphic logs of 19 dune cores and three sections from which 14C and IRSL dates were obtained are presented in Figures 5–7. Subdune sediments were recovered in 13 of the 22 cores taken and were also present in the three sections logged. Sand with rounded gravel and coarse shell fragments, interpreted as wave-lain, was penetrated in four cores (HI1, RL1, DR1 and Boulmer), clay-rich diamicts, interpreted as glacial tills, occurred in three cores (HI2, HI3 and DR2), peat was present in four cores (STA1A, AB1, DR4 and DR5) and the three sections (ALN2, ALN2A and AB2), and stone-free muds, interpreted as estuarine, were found in two cores (NL1 and ALN1). Till was also encountered below peat in several cores and the estuarine mud in NL1 contained a thin (1 cm thick) peat layer 8 cm below its surface. The cores containing estuarine muds were from sites near to modern estuaries in embayment dune systems. Those with sand and gravel, till, and peat showed no particular concentration with respect to physical setting. Except with respect to 14C dates obtained on peat samples and the pollen content of estuarine mud in core NL1, the characteristics of these subdune sediments are not considered further. The dune sands have been grouped into facies (A–C) on the basis of presence/absence of both sedimentary structures and
Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 219
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I
RL2
Ross Links
I
Ross Point
I
Road
N
Ross
Figure 3 Examples of dune system setting and morphology: (A) Holy Island; (B) south-central Druridge Bay; (C) Beadnell Bay/Newton Links; (D) Ross Links. Core locations and positions of selected GPS surveyed profiles are shown. Marginal grid lines are at 1 km intervals.
220 The Holocene 11 (2001)
12
Holy Island
A
10
HI4 south
north
8 6 4 2 0 0
100
200
300
400
500
600
700
800
12
Druridge Bay
B DR1
10 west
east
8 6
Metres OD
4 2 0 0
100
200
300
350
16
Beadnell Bay/Newton Links
C
14
NL2
12
west
east
10 8 6 4 2 0 0
50
100
150
200
250
300
350
16 D
14 12
Ross Links
RL3
west
east
10 8
RL3A RL2
6 4 2 0 0
200
400
600
800
1000
Metres Figure 4 GPS surveyed profiles across dune systems: (A) Holy Island; (B) Druridge Bay; (C) Beadnell Bay/Newton Links; (D) Ross Links. Intersected core locations are indicated. For profile positions, see Figure 3.
stratified units may occur. Some thin (⬍10 cm thick) shell-rich and/or organic-stained (soil) horizons present. Facies B: Massive to moderately well-stratified, fine- to mediumgrained, well-sorted sand (0.5–4 m thick) interbedded with organic (soil and/or peat) horizons up to 60 cm thick. Facies C: Massive to vaguely stratified, fine- to medium-grained, well-sorted sand (1.3–6 m thick) containing very few shell-rich and/or organic-stained horizons. Not all facies occur in all cores/sections: in some a single facies is present (e.g., CW1, HI2 and RL3); others contain all three (e.g., AB1 and DR3) but they do not always occupy the same stratigraphic position and are not of similar thickness within and between sites. Therefore it is not possible to correlate between cores on a facies basis. Individual facies are of approximately equal occurrence (A:14, B:11, C:10; including the three cores not shown in Figures 5–7). The most common stratigraphic relationship is facies A overlain by facies B (six occurrences). Four of these are from dune systems within embayments (Newton Links, Alnmouth and Druridge Bay); the other two are from Ross Links. Dune sediments Results of grain-size analysis are summarized in Figure 8 using median size and skewness parameters. Marked variations in both parameters are evident within and between sites. The overall range (1.4–3.3) and distribution of median sizes indicate that many of the samples are either coarser or finer than those usually found in coastal dunes (cf. Pye and Tsoar, 1990) although the medianskewness relationship is similar to that recorded elsewhere for dunes (e.g., Pye, 1982). The clear separation between core data sets is regarded as reflecting characteristics of the dune-sand source-sediment. A fluvial/estuarine sediment contribution to the shoreline at Newton Links may account for the generally finer median sizes found there; the other sites are dominated by onshore and/or longshore sediment supply. Variations in CaCO3 content are also evident both within and between sites (Table 2). For all samples, Ross Links and Druridge Bay have similar CaCO3 mean values but the range of values at the former site is less than half that at the latter; samples from Newton Links possess the greatest range and mean value and this may reflect the influence local estuarine sediments have had on CaCO3 supply. For individual core runs the highest CaCO3 mean value in each core was recorded from the deepest run selected for analysis. Taken together the spatial and stratigraphic zonation exhibited by these data strongly suggests that local controls, principally source sediment and wave focusing along a crenellate coastline, have had a major influence on dune sediment characteristics. Pollen analysis The subdune mud in core NL1 has a pollen spectrum dominated by Gramineae and Cyperaceae but also contains taxa indicative of saline conditions including Glaux maritima, Plantago maritima, Spergularia and Triglochin spp. (J.B. Innes, personal communication, 1998). These results, along with the proximity of the core site to the present-day estuary (Figure 3C) and altitude of the mud (c. 2–3m OD), suggest the mud is most likely of estuarine origin. 14
horizons containing organic matter. Facies boundaries are often poorly defined or graded on a decimetre scale. Facies descriptions are adapted from those compiled for dune sands in north Norfolk (cf. facies C–E of Knight et al., 1998): Facies A: Massive to well-stratified, fine- to medium-grained, well-sorted sand (0.75–9 m thick). Both horizontal and cross-
C and IRSL age estimates Results of 14C and IRSL age determinations are indicated on Figures 5–7. Details of 14C dates are provided in Table 3 and of IRSL dates in Table 4. A few 14C dates are anomalous: AA-23493 (⬎30 000 years) from Ross Links (RL4) is clearly too old, given its stratigraphic position. The 14C date was obtained from soil organic material and has a ␦13C value of −23.1 per mil. This value is much lower than the range found for peats listed in Table 3, namely –27.5 to –30.5 per mil. Just above this sample is another
a Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 221
Ross Links (RL 3)
Elevation m OD 12
Elevation m OD 12
IRSL : 501+/-34
11
11
Holy Island (HI 4) 10
10
Cheswick (CW 1)
Holy Island (HI 2)
9
IRSL : 469+/-51
8
A
8
RC: M odern IRSL : 245+/-35
B
A
IRSL : 579+/-43
Ross Links (RL 2)
RC: 2585+/-45 IRSL : 275+/-50
7
6
9
Ross Links (RL 1)
IRSL : 238+/-35
Holy Island (HI 1)
C
7
Ross Links (RL 4)
RC: 335+/-45 IRSL : 358+/-38 RC: 990+/-45
6
Ross Links (RL 3A)
B
C
5
5
B
4
4 C
IRSL : 423+/-46
A
RC: M odern
B
IRSL : 350+/-44
3
IRSL: 342+/-37 RC: 5030+/-55
IRSL : 323+/-38
RC: 1030+/-45
IRSL : 667+/-48
3
RC: >30,000
A
a 2
2
A
Figure 5 Lithostratigraphic logs of dune cores from Cheswick, Holy Island and Ross Links showing facies (A–C) and IRSL and explanation of symbols, see Figure 6.
14
C (RC) dates. For
Newton Links (NL 2)
Elevation m OD 12 12
B
11
10
Elevation m OD
Aeolian sand
Till
Wave-lain sand and gravel
Roots
Coarse shell layer
Contorted sand
Soil organic matter
Parallel stratification
Peat
Cross stratification
12
11
10
Estuarine mud
IRSL : 432+/-45
9
9
8
A
St. Aidans (STA 1A)
7
IRSL : 664+/-61
Newton Links (NL 1)
B
RC: 3290+/-45 RC: 3635+/-45 RC: 3705+/-50 RC: 4440+/-50
7
A
IRSL : 562 +/-66
A
RC: 960+/-70
RC: 1940+/-40
5
4
Alnmouth (ALN 2A)
Alnmouth (ALN 2)
6
C
8
Alnmouth (ALN 1)
6
RC: 2290+/-140 RC: 2200+/-70
5
IRSL : 409+/-35
B
4
A
IRSL : 915+/-79
3
2
IRSL: 837+/-61
3
RC: 3690+/-60
2
Figure 6 Lithostratigraphic logs of dune cores and exposures from St Aidan’s dunes, Newton Links and Alnmouth showing facies (A–C) and IRSL and 14 C (RC) dates.
222 The Holocene 11 (2001)
Druridge (DR 4)
Druridge (DR 5)
Elevation m OD 10
Amble (AB 1)
IRSL : 821+/-94
A
IRSL : 696+/-61
RC: 2420+/-60
RC: 785+/-60 RC: 1045+/-60 RC: 1485+/-60
9
9
Druridge (DR 3)
C IRSL : 621+/-69
8
a Elevation m OD 10
B B
8
C
7
7
Amble (AB 2)
RC: 1070+/-45
IRSL : 430+/-59
Druridge (DR 1)
6 A
6
B
Druridge (DR 2)
5 C
IRSL : 620+/-57
A
IRSL : 503+/-59
C
RC: 980+/-40
4
4
RC: 540+/-40 A IRSL : 762+/-69
RC: 1170+/-40 RC: 1290+/-40 RC: 1590+/-45
a
B
5
IRSL : 376+/-36
3
3
RC: 2410+/-60
Figure 7 Lithostratigraphic logs of dune cores and exposures from Amble and Druridge Bay showing facies (A–C) and IRSL and explanation of symbols, see Figure 6.
0.6
Inclusive graphic skewness
Site (core)
0.4
0.2
0.0
-0.2
-0.4
2
3
C (RC) dates. For
Table 2 Summary % CaCO3 values
Ross Links (RL3) Newton Links (NL2) Druridge (DR3)
1
14
4Ø
Median size
Figure 8 Bivariate (median/skewness) scattergram for dune sand sediments from three cores.
organic sand for which a 14C age of 1030 ± 45 years (AA-23492) was obtained. It had a low ␦13C value, −23.4 per mil, and the age should also be considered as an overestimate. AA-23490 (5030 ± 55 years), again from Ross Links (RL1), is also too old compared with the IRSL age of 342 ± 37 years for the sand immediately above it. Again the 14C date was obtained for soil organic material and has a very low value for ␦13C, namely –21.5 per mil. Likewise at Holy Island (HI2), AA-23487 (2585 ± 45 years) was obtained on soil organics and is too old, given its position between two sand units with IRSL dates of 245 ± 35 and 275 ± 50 years. For this sample the ␦13C value of –26.3 per mil appears to be acceptable; however, there are also two younger 14C dates on peats lower in the same section. At Amble (AB1), AA-23499 (1070 ±
Ross Links (RL3)
Newton Links (NL2)
Druridge Bay (DR3)
All samples (n) Maximum Minimum x
320 4.37 0.91 3.01
247 31.54 2.87 8.77
346 8.89 0.81 3.22
Deepest run x
3.67
9.45
5.29
45 years) was also obtained on soil organics with a ␦13C of –25.5 per mil. This is also too old compared with the underlying IRSL age of 620 ± 57 years and the 14C age on the uppermost peat. The remaining 14C date on soil organic material, namely AA23504 (540 ± 40 years) from Druridge Bay (DR2), is consistent with the IRSL age and also has a ␦13C value (–27.9 per mil) that is within the range of the peat samples. It thus appears that the ␦13C values can be used to assess the reliability of the 14C ages in this region. The probability is that the soil organic materials contained wind-blown fragments of older carbon derived from offshore peats or Coal Measures. At several sites (St Aidan’s (STA1A), Alnmouth (ALN2A), Amble (AB1) and Druridge (DR5)) three or more 14C age determinations were obtained on thin (⬍5 cm) slices of peat from interbedded sand-peat layers at the base of the aeolian sequences. Although certain pairs of dates from individual locations are statistically inseparable at either the 1 or 2 level, the general
Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 223
Table 3 Radiocarbon dates from coastal dunes in Northumberland Core/ section code
Sample elevation m OD
14
Material
Laboratory code
C age (years BP ± 1)
␦13C ‰ Calibrated age (years BP ± 2)
Method
Holy Island HI2 7.71–7.60 HI2 7.20–7.10 HI2 6.66–6.59 HI2 6.42–6.40
Soil organics Soil organics Peat Peat
AA-23486 AA-23487 AA-23488 AA-23489
Modern 2585 ± 45 335 ± 45 990 ± 45
–27.6 –26.3 –28.1 –27.5
– 2770 (2739) 2523 502 (442, 371, 331) 296 971 (929) 782
AMS AMS AMS AMS
Ross Links RL1 2.97–2.93 RL2 3.66–3.62 RL4 3.13–3.09 RL4 2.80–2.79
Soil Soil Soil Soil
AA-23490 AA-23491 AA-23492 AA-23493
5030 ± 55 Modern 1030 ± 45 ⬎30 000
–21.5 –25.8 –23.4 –23.1
5910 (5745) 5640 – 1034 (943) 907 –
AMS AMS AMS AMS
St Aidan’s Dunes STA1A 4.50–4.49 STA1A 4.42–4.41 STA1A 4.38–4.37 STA1A 4.28–4.27
Peat Peat Peat Peat
AA-23494 AA-23495 AA-23496 AA-23497
3290 ± 45 3635 ± 45 3705 ± 50 4440 ± 50
–27.9 –27.9 –28.2 –28.4
3627 4079 4167 5293
(3484) 3400 (3936) 3843 (4071, 4028, 4005) 3905 (5040) 4867
AMS AMS AMS AMS
Newton Links NL1 2.84–2.83
Peat
AA-23498
3690 ± 60
–28.6
4170 (4060, 4050, 3990) 3850
AMS
Alnmouth Dunes ALN2 5.12–5.11 ALN2A 5.80–5.79 ALN2A 5.44–5.43 ALN2A 5.38–5.37
Peat Peat Peat Peat
SRR-5750 Beta-109526 Beta-109527 Beta-109528
1940±40 960±70 2290±140 2200±70
–27.5 –27.6 –30.5 –30.0
1972 980 2730 2350
(1880) 1807 (920) 720 (2330) 1960 (2290, 2260, 2160) 2010
Conventional Conventional Conventional Conventional
Amble Dunes AB1 6.60–6.51 AB1 4.09–4.06 AB1 3.78–3.74 AB1 3.71–3.69 AB1 3.52–3.47 AB2 2.50–2.49
Soil organics Peat Peat Peat Peat Peat
AA-23499 AA-23500 AA-23501 AA-23503 AA-23502 Beta-109525
1070 ± 45 980 ± 40 1170 ± 40 1290 ± 40 1590 ± 45 2410 ± 60
–25.5 –28.4 –28.9 –29.1 –28.3 –28.3
1066 956 1181 1287 1554 2720
(964) (926) (1070) (1251) (1507) (2370)
926 782 976 1153 1373 2330
AMS AMS AMS AMS AMS Conventional
Druridge DR2 DR4 DR5 DR5 DR5
Soil organics Peat Peat Peat Peat
AA-23504 AA-23505 AA-26346 AA-26347 AA-26353
540 ± 40 2420 ± 60 785 ± 60 1045 ± 60 1485 ± 60
–27.9 –29.0 –28.6 –28.8 –28.4
637 2725 785 1070 1520
(537) (2380) (690) (950) (1360)
517 2330 660 810 1280
AMS AMS AMS AMS AMS
Bay 3.96–3.90 9.47–9.46 9.19–9.18 9.08–9.07 8.79–8.74
organics organics organics organics
conformable nature of these ages suggests they provide reliable maximum estimates for aeolian activity at those sites. The dates indicate the earliest phases of aeolian activity and dune-building were after c. 3700 14C years BP (c. 4000 cal. years BP) at Newton Links (NL1) and after c. 3300 14C years BP (c. 3500 cal. years BP) at St Aidan’s (STA1A). There is then a considerable timegap prior to aeolian activity and dune construction after c. 2400 14C years BP (c. 2400 cal. years BP) at Amble (AB2) and Druridge Bay (DR4), at c. 2300–950 14C years BP (c. 2300– 900 cal. years BP) at Alnmouth (ALN2 and ALN2A), at c. 1600– 1000 14C years BP (c. 1500–900 cal. years BP) at Amble (AB1) and c. 1500–800 14C years BP (c. 1350–700 cal. years BP) at Druridge Bay (DR5). IRSL age estimates range from 915 ± 79 to 238 ± 35 years (ALN1/4 and HI4/2 respectively) placing aeolian activity and deposition of the dated sand between ad 1083 and 1760. Of the 26 age determinations, 19 fall within the 500-year period ad 1300–1800 and four overlap with the start of that period; the other three ages (NL1/3, ALN1/4 and DR4/2) occur within the preceeding 300 years. In three cores (CW1, NL2, and AB1) 3–5 m of
dune sand has accumulated in a very short time, as indicated by the IRSL dates with overlapping error terms.
Discussion It is generally accepted that coastal dune development is dependent on a supply of suitably sized beach sediment and onshore winds of sufficient strength to transport sand into an accommodation space (e.g., Pye, 1983; Carter, 1988; Klijn, 1990b). However, there is less consensus about the forcing or triggering factors that control phases of dune development. Changes in RSL, changes in climate, and/or human-related activities in the coastal zone are cited frequently as underlying causes of dune building (e.g., Christiansen et al., 1990; Klijn, 1990a; Wilson and Braley, 1997). Absolute age estimates, from dune sediments and organic materials within and below dunes, that correspond broadly with known patterns of environmental change, have been used to assert the role of these trigger mechanisms; but absolute age estimates can demonstrate only a coincidence of timing between dune-
Depth (m)
1.2 5.52 3.0 1.27 1.82 2.15 1.55 7.14 5.35 1.2 5.15 2.15 1.25 2.2 3.41 8.64 1.3 3.65 1.15 4.6 1.4 0.89 1.15 3.55 1.08 1.15
De (Gy)
0.865 ± 0.085 0.887 ± 0.087 0.595 ± 0.065 0.449 ± 0.061 0.540 ± 0.094 0.677 ± 0.063 0.454 ± 0.063 0.636 ± 0.074 0.511 ± 0.051 0.765 ± 0.039 0.892 ± 0.053 0.968 ± 0.052 0.794 ± 0.065 1.002 ± 0.056 0.590 ± 0.054 0.620 ± 0.044 0.884 ± 0.097 1.401 ± 0.102 1.032 ± 0.104 1.405 ± 0.077 0.645 ± 0.041 1.279 ± 0.092 0.585 ± 0.070 0.812 ± 0.084 1.590 ± 0.123 1.118 ± 0.069
Sample
CW1/2 CW1/6 HI1/4 HI2/2 HI2/3 HI2/4 HI4/2 HI4/8 RL1/6 RL3/2 RL3/6 RL3A/3 STA1/2 NL1/3 NL2/4 NL2/9 ALN1/2 ALN1/4 AB1/2 AB1/5 DR1/2 DR2/2 DR3/2 DR3/4 DR4/2 DR5/2
8.23 ± 0.06 9.90 ± 0.10 10.02 ± 0.15 9.38 ± 0.16 10.48 ± 0.09 9.69 ± 0.16 10.02 ± 0.07 9.43 ± 0.07 10.75 ± 0.11 10.24 ± 0.08 9.41 ± 0.16 9.28 ± 0.07 7.45 ± 0.06 9.56 ± 0.07 12.53 ± 0.19 11.88 ± 0.19 7.02 ± 0.18 9.40 ± 0.09 9.66 ± 0.15 13.49 ± 0.12 8.33 ± 0.15 8.68 ± 0.15 6.82 ± 0.12 10.67 ± 0.18 6.55 ± 0.08 9.69 ± 0.10
Kint (%) 0.95 ± 0.07 0.77 ± 0.09 0.74 ± 0.09 0.71 ± 0.09 0.89 ± 0.09 1.02 ± 0.13 0.58 ± 0.08 0.61 ± 0.10 0.46 ± 0.04 0.40 ± 0.05 0.54 ± 0.06 0.54 ± 0.05 0.41 ± 0.04 0.35 ± 0.03 0.42 ± 0.04 0.45 ± 0.05 0.55 ± 0.07 0.50 ± 0.06 0.56 ± 0.07 1.63 ± 0.14 1.08 ± 0.13 0.90 ± 0.09 0.52 ± 0.09 0.79 ± 0.08 1.96 ± 0.18 1.20 ± 0.09
U (ppm) 1.56 ± 0.23 2.64 ± 0.29 2.18 ± 0.27 2.25 ± 0.28 2.21 ± 0.27 3.53 ± 0.42 2.66 ± 0.25 2.86 ± 0.31 1.16 ± 0.14 1.65 ± 0.15 1.83 ± 0.21 1.76 ± 0.17 1.00 ± 0.13 1.01 ± 0.10 1.11 ± 0.14 1.51 ± 0.18 2.06 ± 0.23 2.13 ± 0.20 2.39 ± 0.21 5.19 ± 0.46 4.28 ± 0.43 2.52 ± 0.29 2.53 ± 0.28 2.04 ± 0.26 4.18 ± 0.57 2.21 ± 0.29
Th (ppm) 43 ± 69 47 ± 75 42 ± 67 42 ± 67 47 ± 75 58 ± 83 41 ± 65 43 ± 69 25 ± 39 27 ± 43 33 ± 52 32 ± 51 21 ± 34 20 ± 31 23 ± 36 27 ± 44 35 ± 56 34 ± 57 38 ± 61 96 ± 153 70 ± 113 50 ± 80 38 ± 61 42 ± 68 98 ± 156 54 ± 87
␣ 473 ± 40 566 ± 47 573 ± 48 536 ± 45 599 ± 50 554 ± 47 573 ± 48 539 ± 45 615 ± 52 586 ± 49 538 ± 46 531 ± 44 426 ± 36 547 ± 46 717 ± 61 679 ± 57 402 ± 34 538 ± 45 553 ± 47 771 ± 64 476 ± 41 497 ± 42 390 ± 33 610 ± 52 374 ± 31 554 ± 46
int 764 ± 13 909 ± 16 703 ± 15 713 ± 14 766 ± 11 713 ± 10 731 ± 13 739 ± 16 499 ± 8 481 ± 8 559 ± 11 466 ± 9 376 ± 7 306 ± 6 305 ± 7 482 ± 9 667 ± 13 547 ± 12 579 ± 17 727 ± 14 559 ± 20 600 ± 13 461 ± 13 513 ± 12 755 ± 15 489 ± 14
ext 380 ± 14 460 ± 17 378 ± 16 355 ± 16 388 ± 16 414 ± 21 388 ± 14 401 ± 18 243 ± 8 253 ± 9 295 ± 12 262 ± 10 198 ± 8 166 ± 6 183 ± 8 250 ± 10 291 ± 14 288 ± 12 311 ± 12 549 ± 27 431 ± 26 345 ± 17 290 ± 16 310 ± 16 527 ± 34 327 ± 17
␥
Table 4 Equivalent dose (De), burial depth, K content of feldspar grains, U and Th contents from alpha counting, dose rates in Gy/year, and calculated IRSL age
180 113 145 180 165 159 173 92 111 181 114 161 179 160 138 79 178 135 182 121 176 188 182 136 183 182
Cosmic
1842 ± 82 2095 ± 92 1842 ± 86 1826 ± 84 1966 ± 93 1892 ± 98 1906 ± 83 1815 ± 86 1493 ± 66 1527 ± 67 1539 ± 71 1451 ± 70 1195 ± 52 1197 ± 57 1365 ± 72 1518 ± 74 1573 ± 68 1535 ± 72 1662 ± 80 2265 ± 169 1713 ± 124 1679 ± 94 1360 ± 73 1612 ± 88 1938 ± 164 1607 ± 101
Total
469 ± 51 423 ± 46 323 ± 38 245 ± 35 275 ± 50 358 ± 38 238 ± 35 350 ± 44 342 ± 37 501 ± 34 579 ± 43 667 ± 48 664 ± 61 837 ± 61 432 ± 45 409 ± 35 562 ± 66 915 ± 79 621 ± 69 620 ± 57 376 ± 36 762 ± 69 430 ± 59 503 ± 59 821 ± 94 696 ± 61
Age (yr)
224 The Holocene 11 (2001)
a
aaa Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 225
building phases and environmental changes and are therefore suggestive rather than conclusive indicators of causal factors (cf. Ballantyne, 1991). This distinction is important with respect to dune formation along the coast of Northumberland. All 14C and IRSL age estimates pertinent to dune development are presented in Figure 9. Also included are markers representing the peaks in Holocene RSL for northern, central, and southern sectors of the coast, as reported by Shennan et al. (2000), and periods of significant climatic deterioration in the North Atlantic region as determined from historical records and/or proxy sources (Meese et al., 1994; Lamb, 1995; O’Brien et al., 1995; Bond et al., 1997). Although archaeological materials and palynological evidence for forest clearance and intensive agricultural land use are well documented for the late-Holocene period along the coast of Northumberland (Anon, no date; Innes and Frank, 1988; Innes, 1999), the role of human activity in the development of dunes has not been evaluated by previous researchers. For this reason cultural phases are not included in Figure 9 and we do not speculate on the possible timing or scale of human impacts. Relative sea-level changes and coastal dune development The Northumberland RSL curves of Shennan et al. (2000) demonstrate north–south gradients in both the timing of peak sea levels and the elevations above OD attained by those peaks (Figure 2). The curves demonstrate that each sector of the coast was characterized by a transgressive shoreline during the early and middle Holocene and by a regressive shoreline from c. 4000–3000 cal. years BP to the present day. Models of coastal dune development in relation to changes in RSL generally identify dune-building episodes in association with both rising and falling RSL (e.g., Pye, 1984; Christiansen and Bowman, 1986). During periods of rising RSL, transgressive dunes move onshore as a result of high rates of sand supply from shoreline erosion and/or dune reworking. Longshore drift of sand from eroding shorelines may concentrate sand elsewhere along the coasts and stimulate dune development in areas where shorelines are stable. In periods of falling RSL the lowering of wave base may cause the release and transport towards the shoreline
3000
2000
1000
Little Ice Age
0
aa a a
4000
of more intertidal sand, leading to progradation and subsequent aeolian activity. Consideration of Northumberland dune-building episodes relative to local RSL peaks (Figure 9) suggests most dune systems in Northumberland are associated with regressive shorelines consequent upon sea-level fall. Only in central Northumberland, at St Aidan’s, do 14C dates indicate that some sand accumulation occurred prior to RSL attaining its Holocene peak. At the other central Northumberland site of Newton Links, the 14C-dated peat is from within estuarine muds below the dunes (Figure 6) and its stratigraphic position indicates a further RSL rise and then fall prior to dune initiation. St Aidan’s is therefore anomalous among our Northumberland sites in having sand that apparently pre-dates the RSL peak. However, this sand consists of a thin (⬍5 cm thick) sand unit near the top of the basal peat bed (Figure 6). Samples of peat taken from immediately above and below the sand unit returned overlapping 14C ages (cal. 2 range; Table 3), suggesting that sand deposition was a short-lived, perhaps a one-off, event. However, it is not known whether this sand was emplaced by aeolian processes or was the result of a tidal surge. Given that wet ground conditions and peat accumulation prevailed at the site, it is thought highly unlikely that such a thin sand layer was deliberately spread by the contemporary occupants of the area in an attempt to create land for agriculture. The main phase of dune emplacement at St Aidan’s, after 3290 14 C years BP (3627–3400 cal. years BP), may also have begun before the RSL peak (c. 3200 cal. years BP) was reached (Figure 9). However, if the dated peat was originally thicker and underwent erosion prior to sand accumulation, the 14C age would represent a substantial overestimate for the beginning of dune development. Support for this latter scenario of peat erosion and significantly later sand accumulation is provided by the IRSL age of 664 ± 61 years (STA1/2, Table 4) from sand c. 1 m above the peat (Figure 6). The earliest aeolian activity and dune phases recorded in north and south Northumberland, and later dune phases in central Northumberland, post-date the respective RSL peaks and are therefore associated with regressive shorelines (Figure 9). In north Northumberland dunes appear to be everywhere absent until prior to
Cheswick
(CW1) (HI1)
Holy Island
(HI2) (HI4)
Ross Links
(RL1) (RL3)
(RL3A)
St. Aidan’s Newton Links
(STA1A) (NL1) (NL2)
(ALN1)
Alnmouth
(ALN2)
(ALN2A)
Amble
(AB1) (AB2)
(DR1) (DR2)
Druridge Bay
(DR3) (DR4) (DR5)
Northumberland North
RSL peak
Northumberland Central
RSL peak
Calibrated 14C age (2σ range) of sample at base of or below aeolian sequence.
Calibrated 14C age (2σ range) of sample from interbeds close to base of aeolian sequence Calibrated 14C age (2σ range) of sample from within aeolian sequence
Northumberland South
IRSL age range
14C ages from base and top of peat bed
Sand deposition in relation to 14C age
4000
RSL peak
3000
2000
1000
0 years cal. BP AD 1950
Figure 9 Radiocarbon and IRSL age estimates from Northumberland dunes. The vertical stippled zones represent periods of climatic deterioration (cooling) in the North Atlantic region based on proxy and historical records.
226 The Holocene 11 (2001)
c. 1000 cal. years BP. The lack of earlier dunes may reflect a sampling failure, but given the wide spatial coverage of core sites (Figure 1) a real absence is the preferred explanation. The rate and style of shoreline progradation and sediment availability may not have been conducive for dune development until within the last millennium when RSL was c. +1 m OD (Figure 2). Several sites in south Northumberland have basal peats that provide maximum ages for dune formation (Figure 9). Assuming there was no erosion of these peats prior to sand deposition, then aeolian sands began to accumulate at different times between c. 2700 and 1300 cal. years BP as RSL was falling. At Amble (AB1) several thin layers of sand, interbedded with peat occur at the base of the core (Figure 7). The number of sand-peat alternations, and conformable nature of the 14C dates obtained, indicate several sand-input events between 1554 and 782 cal. years BP. Only after 956–782 cal. years BP was sand input sufficient to terminate peat growth and build dunes. The dating evidence indicates that the development and persistence of coastal dunes in Northumberland is associated with macroscale changes in RSL over the last 4000–5000 years. However, the north–south gradients in RSL change are not entirely matched by gradients in dune development phases. The lack of consistent regional trends in dune development may reflect site-specific conditions in relation to RSL trends as well as the absence of dated index points to constrain the RSL curves over the last 3000 years. Consequently rates of RSL change and any small-scale, short-term reversals in trends within this time interval are unknown. Without such data detail assessment of RSL change in dune development cannot be fully evaluated. Climatic changes and coastal dune development Climate change is a potential forcing factor for Northumberland dune development because periods of consistent onshore-directed (easterly) winds are required in order to explain the landward aeolian transport of beach sand. Presently the area is dominated by winds with offshore-directed westerly components (Table 1). Holocene climate of the North Atlantic region is known to have been punctuated by a series of abrupt millennial-scale shifts during which cool, ice-bearing waters originating north of Iceland were advected south to the latitude of the British Isles. Atmospheric circulation above Greenland also changed abruptly at about the same times. Proxy-records documenting these shifts have been derived from the GISP2 (Greenland) ice core and North Atlantic sediment cores (Meese et al., 1994; O’Brien et al., 1995; Bond et al., 1997). In the period covered by dune development in Northumberland four phases of climatic deterioration are known to have occurred (Figure 9). The most recent of these, the ‘Little Ice Age’ (LIA), occurred between ad 1300 and 1900 (650–50 cal. years BP), with dates varying by up to 200 years. Earlier coolings centred on 1400 cal. years BP, 2800 cal. years BP and 4200 cal. years BP are considered as LIA-type events because they show the same degree of cooling and similar associated shifts in synoptic climate. The IRSL age determinations show that the greatest volumes of recovered dune sediment in Northumberland accumulated in the LIA (Figures 5–7 and 9). Because the basal aeolian sands were not recovered in several of the cores and not dated in others from which they were recovered, we do not know in some cases whether the dated samples are associated with dune initiation at the sites or represent a subsequent phase of development. However, it may reasonably be inferred that the bulk of the ridges containing the core sites, and ridges seaward of those sites, formed either within this relatively narrow time window or later. The presence of a Second World War defensive structure at Ross Links indicates that some post-ad 1945 dune development has occurred at that site. Archaeological and cartographical evidence to support the IRSL dates and therefore LIA dune-building is
available from Holy Island. The Anglo-Saxon farmstead of Green Shiel (Figure 3A) was occupied during the middle and later parts of the ninth century ad and is now surrounded by substantial dunes that have encroached across the ridge and furrow field system (O’Sullivan and Young, 1995). Dune development clearly post-dates occupation of the site. Some dunes were in place by the early part of the seventeenth century as they are shown schematically on a map of the island published in ad 1610 by John Speede (O’Sullivan and Young, 1995). Episodes of significant aeolian sand accumulation during the LIA are documented for a number of locations in northwestern Europe (e.g., Ceunynck, 1985; Klijn, 1990a; Tooley, 1990; Lamb, 1991; Pye and Neal, 1993; Clemmensen et al., 1996; Wilson and Braley, 1997; Clarke et al., 1999; Gilbertson et al., 1999). Therefore this period was one which witnessed dunefield activity on a regional scale. However, most of the examples cited above are drawn from west-coast locations; there are very few known examples of LIA dune development at east-coast sites (cf. Knight et al., 1998; Orford et al., 2000). Grove (1988) and Lamb (1995) have established the climatic characteristics of the LIA from a variety of proxy and historical records. These indicate that the period was not a single phase of sustained cold but one of major and very sudden fluctuations in climate, often lasting only decades; in essence it was a period of both warm and cold climatic anomalies that varied in degree and importance geographically. In cold phases of the LIA, North Atlantic polar waters spread south to the latitude of the Shetland Islands, displacing warmer surface waters and cyclonic storm tracks farther south, and favouring extension and intensification of the Fenno-Scandinavian anticyclone and associated easterly airflow across the British Isles. In LIA warm phases westerly flow and cyclonic activity were re-established as the dominant synoptic conditions affecting the British Isles. As a consequence of the southward shift of the oceanic polar front there was a marked strengthening of the Atlantic’s thermal gradient between latitudes 50–65° N and an increasing propensity for severe storms and storm surges around the coast of the British Isles (Lamb, 1991). Evidence has also been presented by Lamb (1991; 1995) for a fall in North Sea RSL of up to 0.5 m during the LIA, as a result of global glacier advances, but no direct evidence of RSL signature at this time has yet been detected for Northumberland. Nevertheless, short-term climate shifts during the LIA seem to have generated conditions conducive to dune development on both east and west coasts of the British Isles at different times (e.g., Pye and Neal, 1993; Wilson and Braley, 1997; Gilbertson et al., 1999; Orford et al., 2000), but at present IRSL dating resolution does not enable depositional events in Northumberland to be linked with individual LIA cold phases or North Sea storms. Furthermore it is not yet possible to establish whether overlapping IRSL ages from different sites represent synchronous depositional events. The coincidence of timing in coastal dune development over much of northwestern Europe between ad 1300 and 1900 points towards a regional, and probably external, forcing mechanism. At present the climatic anomalies of the LIA may be regarded as the most likely trigger for aeolian activity. The 23 IRSL age determinations that fall either entirely within or overlap with the LIA interval derive from all three facies identified from core inspection (facies A has eight dates, B five and C nine). This indicates that dune-building at the different sites involved more or less continuous sand inputs without prolonged stability intervals (facies A and C), and intermittent inputs of sand separated by brief stability phases in which limited pedogenesis occurred (facies B) (Figures 5–7). The precise stratigraphic signatures of these input regimes were modulated by local-scale factors such as coastal morphology and sediment availability. Late-Holocene cool intervals prior to the LIA are considered as LIA-type events (Meese et al., 1994; Lamb, 1995; Bond et al.,
Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 227
1997). There is some suggestion, from 14C dates on peats, that aeolian sands were accumulating at these times at different sites in Northumberland, but on the evidence available, dune development was not as pronounced as in the LIA. Thin sand layers at Amble (AB1), discussed above, and Druridge Bay (DR5) accumulated in the cool interval that characterised the middle to later part of the first millennium ad (c. 1650–1150 cal. years BP), and sand may have also accumulated at Holy Island (HI2) and Alnmouth (ALN1) during the same interval (Figure 9). This period was one of notable sand drift along the west coast of the southern isles of the Outer Hebrides (Gilbertson et al., 1999) and also witnessed dune growth on the east coast of Scotland (Lamb, 1995). Cool phases at c. 3100–2400 cal. years BP and 4350–3950 cal. years BP may have also been marked, respectively, by dune-building at Druridge Bay (DR4) and Amble (AB2), and by deposition of the thin sand layer at St Aidan’s (see above). If the marked absence of widespread dune formation in cooler climate periods earlier than the LIA reflects a genuine absence at those times, it suggests that the climatic and morphosedimentary conditions of the LIA must have been significantly different in some way to those of earlier cool periods in order to generate dunes. Models of dune development The accumulated evidence suggests that most dune-building in Northumberland was associated with regressive shorelines and periods of climatic deterioration. However, the morphosedimentary expression of these shorelines was not consistent along the coast and resulted in dune systems occupying four contrasting physical settings (see above). In terms of dune substrate, core basal sediments and exposures reveal that dunes developed on either terrestrial sediments (peats and/or tills), at elevations above the RSL maximum, or near-shore marine sediments (estuarine muds or beach sands and gravels), at elevations close to the RSL maximum (Figures 5–7). In the first of these situations, with terrestrial sediments as substrate, the role of RSL change in dune development was principally as a provider of sediment for aeolian entrainment, accommodation space being already available at elevations above RSL maximum, and dunes may have been either transgressive or regressive in nature. In the second situation, with near-shore marine sediments as substrate, RSL change functioned as both provider of sediment and creator of accommodation space, and dunes are likely to have prograded seaward. Thus, both substrate characteristics and site elevation conditioned dune development. Whether dune systems anchored on terrestrial sediments were transgressive or regressive has not been firmly established. The interbedded sand-peat layers at or near the base of several cores may be an expression of transgressive dune or sand sheet activity but cannot be regarded as unequivocal evidence.
Conclusions Detailed assessments of coastal dune systems in Northumberland, northeast England, in relation to changes in RSL and climate, indicate that the overwhelming majority of dunefields, and the sand contained therein, accumulated following the local RSL peak and are therefore associated with regressive shorelines. At only one location (St Aidan’s) is there some evidence for limited sand deposition when the shoreline was in a transgressive mode, prior to the local RSL maximum, but how this sand was emplaced is not known with certainty. Our finding that most dunes are associated with regressive shorelines indicates RSL functioned as a macroscale control, through its influence on sediment supply and accommodation space for dune development. Where dunes are anchored on terrestrial sediment, dune expansion may have been either transgressive or regressive in nature. Where near-shore
marine sediments form the dune substrate, a regressive (prograding) dune model seems most likely. The IRSL age determinations indicate that the greatest quantities of dune sand were emplaced during the LIA. This finding is consistent with several previous statements concerning west European dune activity and suggests a regional-scale climaterelated control on dune-building. The short-term climate shifts that characterized the LIA appear to have produced conditions that allowed dune development on both west- and east-facing coasts of Europe. A fall in North Sea RSL at that time coupled with an increasing propensity for easterly air flow and severe storms may have combined to increase sediment availability and move sand onshore into dunes. However, dating resolution is such that it is not yet possible to link dune-building events with individual LIA cold phases or periods of increased storminess in the North Sea. Some dune development in central and south Northumberland may have occurred during Holocene cool phases that preceded the LIA. However, the evidence for this is based on 14C dating and is less robust than that derived from IRSL dates. The restricted presence of dunes at these times may indicate specific conditions, pertaining in the LIA, were lacking on earlier occasions.
Acknowledgements Thanks are due to the British Geological Survey coring team, Robert Stewart for surveying assistance, Dr Jim Innes for pollen data, and the many landowners for allowing access to their properties. Drs Douglas Harkness and Charlotte Bryant of the NERC Radiocarbon Laboratory facilitated most of the 14C dating. Dr Fiona Musson is thanked for making the IRSL measurements. The figures were prepared by Mark Millar. This paper is LOIS publication No. 780 of the LOIS Community Research Programme; the research was conducted as part of a Special Topic Award (LOEPS 75) from the NERC (GST/02/0789).
References Anon. no date: A strategy for coastal archaeology in Northumberland. Northumberland County Council. Atkinson, D. and Houston, J., editors 1993: The sand dunes of the Sefton coast. National Museums and Galleries on Merseyside and Sefton Metropolitan Borough Council. Ballantyne, C.K. 1991: Late-Holocene erosion in upland Britain: climatic deterioration or human influence? The Holocene 1, 81–85. Bond, G., Showers, W., Cheseby, M., Lotti, R., Almasi, P., deMenocal, P., Priore, P., Cullen, H., Hajdas, I. and Bonani, G. 1997: A pervasive millennial-scale cycle in North Atlantic Holocene and glacial climates. Science 278, 1257–66. Boro´wka, R.K. 1990a: Coastal dunes in Poland. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 25–30. —— 1990b: The Holocene development and present morphology of the Leba dunes, Baltic coast of Poland. In Nordstrom, K.F., Psuty, N.P. and Carter, R.W.G., editors, Coastal dunes: form and process, Chichester: Wiley, 289–313. Bressolier, C., Froidefond, J.-M. and Thomas, Y.-F. 1990: Chronology of coastal dunes in the south-west of France. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 101–107. Carruthers, R.G., Dinham, C.H., Burnett, G.A. and Maden, J. 1927: The geology of Belford, Holy Island and the Farne Islands (2nd edition). Memoirs of the Geological Survey of England and Wales, HMSO. Carter, R.W.G. 1988: Coastal environments. London: Academic Press. —— 1991: Near-future sea level impacts on coastal dune landscapes. Landscape Ecology 6, 29–39. Carter, R.W.G. and Wilson, P. 1993: Aeolian processes and deposits in northwest Ireland. In Pye, K., editor, The dynamics and environmental
228 The Holocene 11 (2001)
context of aeolian sedimentary systems, Geological Society, London, Special Publications 72, 173–90. Ceunynck, R. de 1985: The evolution of the coastal dunes in the western Belgian coastal plain. Eiszeitalter und Gegenwart 35, 33–41. Christiansen, Ch. and Bowman, D. 1986: Sea-level changes, coastal dune building and sand drift, north-western Jutland, Denmark. Geografisk Tidsskrift 86, 28–31. Christiansen, Ch., Dalsgaard, K., Møller, J.T. and Bowman, D. 1990: Coastal dunes in Denmark. Chronology in relation to sea level. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 61–70. Clarke, M.L., Rendell, H.M., Pye, K., Tastet, J-P., Pontee, N.I. and Masse´, L. 1999: Evidence for the timing of dune development on the Aquitaine coast, southwest France. Zeitschrift fu¨r Geomorphologie Supplement-Band 116, 147–63. Clemmensen, L.B., Andreasen, F., Nielsen, S.T. and Sten, E. 1996: The late Holocene coastal dunefield at Vejers, Denmark: characteristics, sand budget and depositional dynamics. Geomorphology 17, 79–98. Devoy, R.J.N., Delaney, C., Carter, R.W.G. and Jennings, S.C. 1996: Coastal stratigraphies as indicators of environmental changes upon European Atlantic coasts in the late Holocene. Journal of Coastal Research 12, 564–88. Duller, G.A.T. 1991: Equivalent dose determination using single aliquots. Nuclear Tracks and Radiation Measurements 18, 371–78. Frank, R. 1982: A Holocene peat and dune-sand sequence on the coast of northeast England – a preliminary report. Quaternary Newsletter 36, 24–32. Galliers, J.A. 1970: The geomorphology of Holy Island, Northumberland. University of Newcastle upon Tyne, Department of Geography Research Series No. 6. Gilbertson, D.D., Schwenninger, J.-L., Kemp, R.A. and Rhodes, E.J. 1999: Sand-drift and soil formation along an exposed North Atlantic coastline: 14,000 years of diverse geomorphological, climatic and human impacts. Journal of Archaeological Science 26, 439–69. Granja, H.M. and de Carvalho, G.S. 1992: Dunes and Holocene deposits of the coastal zone north of Mondego Cape, Portugal. In Carter, R.W.G., Curtis, T.G.F. and Sheehy-Skeffington, M.J., editors, Coastal dunes: geomorphology, ecology and management for conservation, Rotterdam: Balkema, 43–50. Grove, J.M. 1988: The Little Ice Age. London: Methuen. Innes, J.B. 1999: Regional vegetation history. In Bridgland, D.R., Horton, B.P. and Innes, J.B., editors, The Quaternary of north-east England. Field guide, London: Quaternary Research Association, 21–34. Innes, J.B. and Frank, R.M. 1988: Palynological evidence for late Flandrian coastal changes at Druridge Bay, Northumberland. Scottish Geographical Magazine 104, 14–23. Johnson, G.A.L., editor, 1995: Robson’s geology of northeast England. Transactions of the Natural History Society of Northumbria 56. Klijn, J.A. 1990a: The younger dunes in the Netherlands; chronology and causation. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts. Catena Supplement 18, 89–100. —— 1990b: Dune forming factors in a geographical context. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 1–13. Knight, J., Orford, J.D., Wilson, P., Wintle, A.G. and Braley, S. 1998: Facies, age and controls on recent coastal sand dune evolution in north Norfolk, eastern England. Journal of Coastal Research Special Issue 26, 154–61. Lamb, H.H. 1991: Historic storms of the North Sea, British Isles and northwest Europe. Cambridge: Cambridge University Press. —— 1995: Climate, history and the modern world (second edition). London: Routledge. Lunn, A.G. 1995: Quaternary. In Johnson, G.A.L., editor, Robson’s Geology of Northeast England, Transactions of the Natural History Society of Northumbria 56, 297–311. Martin, E. 1988: Relationship between dune formation and Baltic Sea transgressions in Estonia. In Winterhalter, B., editor, The Baltic Sea, Geological Survey of Finland, Special Paper 6, 79–85. Meese, D.A., Gow, A.J., Grootes, P., Mayewski, P.A., Ram, M., Stuiver, M., Taylor, K.C., Waddington, E.D. and Zielinski, G.A. 1994: The accumulation record from the GISP2 core as an indicator of climate change throughout the Holocene. Science 266, 1680–82. O’Brien, S.R., Mayewski, P.A., Meeker, L.D., Meese, D.A., Twickler,
M.S. and Whitlow, S.I. 1995: Complexity of Holocene climate as reconstructed from a Greenland ice core. Science 270, 1962–64. Orford, J.D., Wilson, P., Wintle, A.G., Knight, J. and Braley, S. 2000: Holocene coastal dune initiation in Northumberland and Norfolk, eastern UK: climate and sea-level changes as possible forcing agents for dune initiation. In Shennan, I. and Andrews, J., editors, Holocene land-ocean interaction and environmental change around the North Sea, Geological Society, London, Special Publications 166, 197–217. O’Sullivan, D. and Young, R. 1995: Book of Lindisfarne Holy Island. London: Batsford. Plater, A.J. and Shennan, I. 1992: Evidence of Holocene sea-level change from the Northumberland coast, eastern England. Proceedings of the Geologists’ Association 103, 201–16. Pye, K. 1982: Negatively skewed aeolian sands from a humid tropical coastal dunefield. northern Australia. Sedimentary Geology 31, 249–66. —— 1983: Coastal dunes. Progress in Physical Geography 7, 531–57. —— 1984: Models of transgressive coastal dune building episodes and their relationship to Quaternary sea level changes: a discussion with reference to evidence from eastern Australia. In Clark, M.W., editor, Coastal research: UK perspectives, Norwich: Geobooks, 81–104. —— 1990: Physical and human influences on coastal dune development between the Ribble and Mersey estuaries, northwest England. In Nordstrom, K.F., Psuty, N.P. and Carter, R.W.G., editors, Coastal dunes: form and process, Chichester: Wiley, 339–59. Pye, K. and Neal, A. 1993: Late Holocene dune formation on the Sefton coast, northwest England. In Pye, K., editor, The dynamics and environmental context of aeolian sedimentary systems, Geological Society, London, Special Publications 72, 201–17. Pye, K. and Tsoar, H. 1990: Aeolian sand and sand dunes. London: Unwin Hyman. Radley, G.P. 1992: The dunes of England, an example of a national inventory. In Carter, R.W.G., Curtis, T.G.F. and Sheehy-Skeffington, M.J., editors, Coastal dunes: geomorphology, ecology and management for conservation, Rotterdam: Balkema, 439–53. Raistrick, A. and Blackburn, K.B. 1932: The late-glacial and post-glacial periods in the North Pennines. Part III – the post-glacial peats. Transactions of the Northern Naturalists Union 1, 79–103. Ritchie, W. and Whittington, G. 1994: Non-synchronous aeolian sand movements in the Uists: the evidence of the intertidal organic and sand deposits at Cladach Mo´r, North Uist. Scottish Geographical Magazine 110, 40–46. Robertson-Rintoul, M. and Ritchie, W. 1990: The geomorphology of coastal sand dunes in Scotland: a review. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 41–49. Robson, D.A. 1982: The geology of Holy Island. Peterborough: Nature Conservancy Council for England. Ross, S. 1992: The Culbin Sands – fact and fiction. Centre for Scottish Studies, University of Aberdeen. Sanjaume, E. and Pardo, J. 1992: The dunes of the Valencian coast (Spain): past and present. In Carter, R.W.G., Curtis, T.G.F. and SheehySkeffington, M.J., editors, Coastal dunes: geomorphology, ecology and management for conservation, Rotterdam: Balkema, 475–86. Selsing, L. and Mejdahl, V. 1994: Aeolian stratigraphy and thermoluminescence dating of sediments of late Holocene age from Sola, southwest Norway. Boreas 23, 92–104. Shennan, I., Lambeck, K., Horton, B., Innes, J., Lloyd, J., McArthur, J. and Rutherford, M. 2000: Holocene isostasy and relative sea-level changes on the east coast of England. In Shennan, I. and Andrews, J., editors, Holocene land-ocean interaction and environmental change around the North Sea, Geological Society, London, Special Publications 166, 275–98. Steers, J.A. 1969: The coastline of England and Wales (second edition). Cambridge: Cambridge University Press. Stuiver, M. and Reimer, P.J. 1993: Extended 14C data base and revised CALIB 3.0 14C age calibration program. Radiocarbon 35, 215–30. Tooley, M.J. 1990: The chronology of coastal dune development in the United Kingdom. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 81–88. Tsoar, H. 1990: Trends in the development of sand dunes along the southeastern Mediterranean coast. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 51–60.
Peter Wilson et al.: Late-Holocene coastal dune development in northeast England 229
van der Meulen, F. 1990: European dunes: consequences of climate change and sealevel rise. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 209–23. Wilson, P. 1990: Coastal dune chronology in the north of Ireland. In Bakker, Th.W.M., Jungerius, P.D. and Klijn, J.A., editors, Dunes of the European coasts, Catena Supplement 18, 71–79.
Wilson, P. and Braley, S.M. 1997: Development and age structure of Holocene coastal sand dunes at Horn Head, near Dunfanaghy, Co. Donegal, Ireland. The Holocene 7, 187–97. Wintle, A.G., Clarke, M.L., Musson, F.M., Orford, J.D. and Devoy, R.J.N. 1998: Luminescence dating of recent dunes on Inch Spit, Dingle Bay, southwest Ireland. The Holocene 8, 331–39.
