Jack Edward Treagus (1935 – 2025)
Structural geologist who made immense contributions to our understanding of Britain’s Caledonian deformation.
Jack Treagus (© Richard Pattrick and Susan Treagus)
Jack Treagus was born in Portsmouth on 20 December 1935 where he attended Portsmouth Northern Grammar, becoming Head Boy. After National Service, he studied geology at the University of Liverpool, where student fieldwork in the deformed and metamorphosed Dalradian of Connemara, Ireland, and the Precambrian of Holy Island, Wales, were to define his future career. He stayed at the university to undertake a PhD on the Moine and Dalradian of Perthshire, Scotland. After short spells in Leeds and Ghana, Jack obtained a lectureship at the University of Manchester in 1966, where he stayed for the rest of his career, teaching structural geology and geological mapping.
Scottish fieldwork
Jack’s forte was in the field, and his research in many challenging regions of the British Isles provided new interpretations based on meticulous field observations of meso- and micro-structures. He leaves a seminal body of work in unravelling the stratigraphy, metamorphism and structural evolution of the Dalradian of the Southwest and Central Highlands of Scotland, from Kintyre to Aberdeenshire. The multiple episodes of Caledonian deformation that Jack identified and correlated right across this terrane now define our understanding of the Dalradian; a host of high-quality publications are characterised by detailed evidence and structural cross-sections in the impressive The Dalradian of Scotland (Geologists’ Association Guide No. 67, 2009).
He leaves a seminal body of work in unravelling the stratigraphy, metamorphism and structural evolution of the Dalradian
Jack later returned to this region of Scotland, as manager and contributor to a major mapping project funded by the British Geological Survey, resulting in the production of a solid geology map sheet and accompanying memoir (Treagus et al. 2001. Schiehallion: Solid Geology Map: Sheet S55w. 1: 50 000 Series Geological Maps, Scotland). Additionally, he redefined the major sinistral fault suite (Loch Tay, Ericht and Tyndrum Faults) of the Central Highland Terrane, and the relative slip components in relationship to epigenetic mineralisation.
Jack also produced a structural reinterpretation of the contorted Hawick Group rocks of the Southern Uplands, was editor for Caledonian Structures in Britain: South of the Midland Valley (Geological Conservation Review Series No. 3, 1992) and contributed to other conservation review volumes. In 2003, he was awarded the Clough Medal, the premier honour of the Edinburgh Geological Society, for his work on the geology of Scotland.
Impactful partnership
Jack had many successful collaborations, but one that (officially) started in 1970 lasted for 55 years; that with his wife Sue. Structural geology brought them together. They published numerous papers together, on folding, strain, and deformed conglomerates. During retirement, they tackled another Precambrian-Cambrian complex, re-interpreting the highly deformed Monian Supergroup of Anglesey, and produced the delightful book, The Rocks of Anglesey’s Coast.
Jack taught structural and field geology at the University of Manchester for 35 years and was much loved by students, his interactions characterised by patience and kindness. He died on 7 March 2025, and is survived by wife Sue, daughters Helen and Jane, and three grandsons.
By Richard Pattrick and Susan Treagus
