Background
The site comprises a varied assemblage of coastal landforms, including sand spits, sand dunes, salt marshes, intertidal sand flats, raised shorelines and a tsunami deposit all developed in a highly dynamic environment (ELC_28 P1). Aspects of the coastal evolution, including its wider setting in the context of the deglaciation of the area, are described by Jackes (1973[1]), Rose (1980)[2], Davies et al. (1986)[3], Firth et al. (1997)[4] and Babtie Group ABP Research & Consultancy Ltd (2002). Jackes (1973)[1], Davies et al. (1986)[3] and Firth et al. (1997)[4] provide geomorphological maps of varying detail.
Quaternary Deposits and Landforms
Shore platforms and raised beaches
The east side of Belhaven Bay displays an assemblage of former shorelines represented by shore platforms and raised beach deposits. A shore platform in the present intertidal zone is cut across gently dipping Carboniferous strata and continues more extensively to the east (see ELC_4 Dunbar Shore). At the back of the present beach, there is a low cliff and a step up to a second (raised) shore platform overlain by a Holocene raised beach that is utilised by the Winterfield Golf Course (ELC_28 P2, P3). Inland to the east, the backing cliff of this platform rises to a higher glaciated shore platform. Good sections in the raised beach deposits reveal shelly sand and gravel deposits (ELC_28 P3).
However, some of the exposures have been covered by coastal defence works (concrete blocks and gabion baskets that are partly collapsing). Hall (2012)[5] notes that the coastal edge has retreated by some 45 m in this area since AD 1854, indicating significant coastal erosion of the soft bedrock cliff. On the Tyninghame shore, an extensive intertidal shore platform also fringes the bay north-east of Sandy Hirst towards St Baldred's Cradle. The platform here is extensively littered with glacial erratics (ELC_28 P4).
Sections in raised beach deposits and blown sand exposed by recent coastal erosion also occur along the south side of the Tyne Estuary near Hedderwick and along the lower part of the incised Hedderwick Burn (Davies et al., 1986[3]). The presence here of gravel layers with rip-up clasts of mud and broken shells may also represent deposits of the tsunami associated with the Holocene Storegga Slide (Hall, 2012[5]; Smith et al., 2012[6]); see also ELC_23 (Lochhouses).
Beach-dune-saltmarsh complexes
The site forms a large sediment sink with significant accumulations of sand in the extensive intertidal sandflats within the Tyne Estuary and the adjacent sand dune systems and sandy beaches (ELC_28 P1). The site is of particular interest for the two sand spits of Sandy Hirst and Spike Island (ELC_28 P1). Sandy Hirst extends south from the north shore of the estuary. It appears to have been a relatively stable feature since first recorded on Ordnance Survey maps in 1853 (Jackes, 1973[1]). On its west side, an extensive area of saltmarsh fringes the bay (ELC_28 P5). Saltmarsh is also present along the south-west margin of the site in front of Buist's Embankment.
Spike Island is a relatively recent recurved spit formed by coastal progradation through the growth and attachment of an offshore sandbank sometime after the 1940s (Jackes, 1973)[1]. A line of sand dunes has built up along the spit and an area of saltmarsh is developing on the former sandflats on its landward side (ELC_28 P1, P6). Inland of these saltings, a line of older dunes marks the former coastal edge. The southern part of the present coastal edge of Spike island is relatively low and appears relatively stable, whereas the seaward edge of the higher dunes towards the north end is cliffed and eroding (ELC_29 P7).
Additional Information
The wider geomorphological setting of the site comprises Lateglacial and Holocene raised beach deposits and a range of glacifluvial landforms and deposits that extend inland from the estuary into adjacent areas of predominantly agricultural land (Jackes, 1973[1]; Davies et al., 1986[3]; Firth et al., 1997[4]). These adjacent features have not been included here, but could be evaluated as part of a revised site assessment in the future.
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