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.
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.
During the Llandovery, the Stockdale Supergroup is marked by a number of oxic-anoxic transitions, with black shales corresponding to transgressions - these may have helped to mitigate a runaway greenhouse effect.
Analysis of the clay mineral illite from a section across the Windermere Supergroup permits an estimate to be made of its maximum burial depth.
[3] At a certain point, the deep water basin changes from an underfilled state, where accommodation space is created as fast as it is filled with flysch, to an overfilled one (stage 3).
The Dent Group, the oldest part of the supergroup, is a good match for the carbonate facies expected in the shallow waters of stages 2–3; accommodation space was created through thermal subsidence.
The end of stage three is represented by the Coniston Group, a series of sandy turbidites, with sediment supply from the north east (and controlled by basement faulting).