Inherited shore platforms
Significance: a cover of till indicates that there is widespread inheritance of shore platforms from before the last ice sheet
On more sheltered shores the shore platform may pass beneath till. If recently uncovered, the platform may carry
striations. Examples include St Catherine's Bay on Stronsay, where a rock
platform striated SE-NW is overlain by 4 m of till. At
Scara Taing, Rousay, a buried platform
or platforms above current sea level but within the range of storm waves display
crossing striae and are overlain by three separate till units. The
widespread burial of shore platforms suggests formation before the
last glacial maximum. This is consistent with the preservation at
sites on NW Hoy of
beach gravels resting on a raised rock platform. Steers (1973) notes that there
are extensive shore platforms emerging from beneath till at just above current
sea level on the northern shore of Scapa Flow.
Orkney lies close to the zero isobase for postglacial sea level rise, a reflection of the position of the islands towards but not at the periphery of the last Scottish ice sheet. Shetland not only developed its own ice cap, it also has a postglacial history which is entirely one of submergence. Orkney has been close to its present sea level for ~3 ka in the current interglacial. Presumably also in earlier interglacial phases sea level stabilised for long periods at close to its present level, allowing protracted periods of platform cutting.
Wide rock platform emerging from beneath till, Bay of Swartmill, Westray