stratigraphy

On the main tools for reconstructing the glacial history of an area is to examine the local stratigraphic record. Tills are firm indicators of the former presence of glacier ice and their fabrics and erratic content provide information about the direction of former ice movement. Where tills are inter-bedded with other sediments, such as meltwater or periglacial deposits then a sequence of events can be built up.

On Orkney, the possibilities for the development of complex stratigraphy has been greatly reduced by the erosive effects of successive ice masses. The latest glaciers tend to erode the loose sediment deposited by earlier ice masses and meltwater. Nonetheless useful information can be provided even when only two tills are superposed at sites such at Denwick and Scara Taing.

  • Westray is the furthest northwest of the Orkney islands. The total area is 47 square kilometres, not huge but the irregular shape gives it a long coastline of almost 80 kilometres, a good place to look for glacial striations. The bedrock of the whole of the island is made up of the cyclical Rousay Flagstone Formation. ...

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  • Glacial deposition is largely confined to low-lying areas on Orkney, where thicknesses of till may exceed 10 m. The glacial deposits drape the landscape, smoothing its outlines. Ice-marginal features are largely unrecognised outside Hoy ...

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  • In the gently-dipping sandstone terrain of Orkney, it is often difficult to pick out classic landforms of glacial erosion. Low-lying areas often show a pronounced SW-NE grain to the topography, parallel to the main direction of ice sheet flow. ...

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  • During the periods of maximum cold in the Quaternary, major ice sheets covered Scotland. An ice stream hundreds of metres thick curved out from the Moray Firth to cross the plain of Caithness and flow over Orkney towards ice limits close to the edge of continental shelf.

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