Matching The Model
Stage 1 is hard to spot in the sedimentary record. The Dent Group, the oldest group 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 deeper water deposits of stage three are represented by the Stockdale and Tranearth groups, which display a steady deepening, as expected of sediments deposited in an underfilled basin, with a sedimentation rate high enough to preserve annual variation in places. (This signal is complicated by an overprinted signature of eustatic glaciations.) 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). The group is subdivided into formations, which each represent a turbidite lobe, and are separated by anoxic background sedimentation. The Kendal Group covers the transition into stage four, with pronounced shallowing up; turbidites become thinner-bedded, and anoxic hemipelagics give way to oxygenated sediments, with storm beds becoming more and more common, and intertidal sediments topping the group. The missing Old Red Sandstone mentioned above formed the molasse sediments of stage 4.
Throughout the Silurian, until the beginning of Old Red Sandstone deposition, sedimentation rate increases steadily, reaching a peak of 1 mm a−1.
Read more about this topic: Windermere Supergroup
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