The Roxby Formation, previously known as the Permian Upper Marls, is a formation from the Guadalupian-Early Triassic of eastern England (formation dies out at Nottinghamshire). The formation is made up largely of mudstone and siltstone, reddish brown, with subordinate sandstone.BSmith, D B, Harwood, G M, Pattison, J and Pettigrew, T H. 1986: A revised nomenclature for Upper Permian strata in eastern England. 9-17 in Harwood, G M and Smith, D B (editors): The English Zechstein and Related Topics. Geological Society Special Publication No.22.
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