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Windermere Supergroup
The Windermere Supergroup is a geological unit formed during the Ordovician to Silurian periods ~, and exposed in the north west of England, including the Pennines and correlates along its strike, in the Isle of Man and Ireland, and down-dip in the Southern Uplands and Welsh Borderlands. It underlies much of north England's younger cover, extending south to East Anglia. It was formed as a foreland basin, in a similar setting to the modern Ganges basin, fronting the continent of Avalonia as the remains of the attached Iapetus ocean subducted under Laurentia.
The supergroup comprises the Coniston group of turbiditic limestones, and the overlying series of shales, grits and greywackes. Compression from the south east during the later Acadian orogeny (probably caused by the closure of the Rheic ocean) buckled the strata into anticlines and synclines and caused slaty cleavage in some sediment beds.
==Before the Windermere: Basement terranes==
To the north west of the unit lies the Cambro-Ordovician Skiddaw Group, a sequence that formed on the Avalonian continental margin, composed mainly of turbidites. Between the two, the Borrowdale Volcanic Group consists of tuffs erupted by an underlying calc-alkaline volcanic arc, active during the subduction of the Iapetus ocean crust.
The Windermere basin was formed by flexure. Prior to its formation, the Southern Uplands accretionary prism, flanking the edge of the Laurentian continent, was advancing towards Avalonia. The load of the mountains formed during this collision weighed down the Avalonian plate, causing the development of accommodation space.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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