Estuarine muds lying above horizontally-bedded sands at Hedderwick
Definition: a name used in Scotland to denote a flat, former estuary surface developed across mud and clay and lying above present sea level
Carse lands are flat lands, coastal plains developed on the raised beds of estuaries. All estuaries are areas of limited wave action. Extensive mud flats will develop if there is a high suspended load in the waters of the estuary, perhaps derived from river mud or from the erosion of mud-rich sediments on the estuary shore. As fresh water becomes brackish, the salt causes the flocculation of clay particles and to sedimentation.
If sea level falls, the surface of the mud flats is colonised by swamp-loving vegetation, like willow. The death of these plants leads to the accumulation of peat on the boggy ground. If the sea level rises, then the peat surface may be covered by new mud. Carse surfaces are thus highly sensitive to small changes in sea level. Equally, the carse mud and peat provide a record of sea level and the existence of former shorelines, now buried and below sea level.
In East Lothian the main areas of carse lie at the mouths of the Tyne and Peffer Burns. The only exposure in carse sediments lies near Hedderwick, where the raised beach sands grade eastwards towards the head of the estuary into raised muds. David Smith has recorded roe deer footprints on the surface of the mud that must be several thousands of years old.
The carse reaches its greatest extent around Stirling. Here the mudflats cover many kilometres and include a number of buried channels of the Forth. Towards Kincardine, the carse clays have yielded many skeletons of marine mammals, including seals and the number of whales.