Chronology of the Windermere supergroup | ||
−450 — – −445 — – −440 — – −435 — – −430 — – −425 — – −420 — – −415 — – −410 — – −405 — – −400 — | Dent Group Stockdale Group Tranearth Group Coniston Gr. Kendal Gr. Old Red Sandstone cover | |
The Windermere Supergroup is a geological unit formed during the Ordovician to Silurian periods ~450 million years ago, and exposed in northwest 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 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 Dent Group of turbiditic limestones, and the overlying series of shales, grits and greywackes of the Stockdale Group, Tranearth Group, Coniston Group and Kendal Group. Compression from the south east during the later Acadian orogeny (probably caused by the closure of the Rheic ocean)[1] buckled the strata into anticlines and synclines and caused slaty cleavage in some sediment beds.