Flandrian, Quaternary, Midland Valley of Scotland
|Cameron, I B, and Stephenson, D. 1985. British regional geology: The Midland Valley of Scotland. Third edition. Reprint 2014. Keyworth, Nottingham: British Geological Survey.|
The Flandrian Stage began 10 000 years B.P. and the deposits include the marine and estuarine sediments associated with the Flandrian transgression, river alluvium, peat and blown sand. Movements of sea level are described above.
The climate during the Flandrian improved from arctic conditions at the end of the Devensian to the Climatic Optimum 5000 to 3000 years B.P. and has since become cooler and wetter. The stage is subdivided into five periods, each characterised by a different climatic regime. The subdivision and the corresponding pollen zones are shown in P915558. The climatic improvement, marking the beginning of Flandrian times, brought widespread periglacial activity to an end and woodland and forest gradually became established. Deforestation, under man’s influence, began about 5000 years B.P.
The carse lands of the Forth, Tay and Clyde estuaries are underlain by marine and estuarine deposits laid down during, and subsequent to the Flandrian transgression which reached its maximum prior to 6500 years
B.P. The deposits consist of marine clay, silt and rarely sand, with layers of shells. At Flanders Moss, near the Lake of Menteith, peat growth was virtually continuous throughout the period of deposition of the Carse Clays.
The raised beach deposits in the outer parts of the estuaries and in the Firth of Clyde consist of sands and gravels locally containing peat layers.
The growth of hill peat is thought to have been initiated in the Atlantic Period, but basin peat may have started accumulating in the Boreal Period. Large areas of lowland peat have been stripped by man and recent erosion is affecting areas of hill peat.
Alluvium commonly forms thin terraced deposits of silt and sand with lenses of gravel along river banks and in lochs where streams enter.
Areas of blown sand occur at Montrose, near Carnoustie and St Andrews and parts of the East Lothian coast in the east and on the Ayrshire coast between Saltcoats and Prestwick in the west.
Flandrian raised beaches
A transgression of the sea occurred in early Flandrian times and it formed the Main Post-Glacial Shoreline prior to 6500 years B.P. at or near the maximum extent of the transgression. The deposition of extensive marine and estuarine deposits, called Carse Clays, took place in the estuaries of the Forth and the Tay contemporaneously with the local accumulation of beds of peat. In the Firth of Clyde sand and gravel beaches formed at many places and are especially prominent in Ayrshire between Ayr and Ardrossan, and at Girvan. The sea also connected with the Loch Lomond basin at the maximum of the Flandrian transgression.
Isostatic tilting resulted in the beach sloping gently eastwards in the Forth and Tay areas and to the south and south-west in the Firth of Clyde.
Since the formation of the Main Post-Glacial Shoreline, sea level has fallen and younger, lower shoreline features have formed.
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