New light on the 1824 William Smith Northumberland County map; a joint work by Smith and Phillips

• Published in: Earth sciences history 2016-01, Vol.35 (1), p.99-114
• Main Author: Pedley, Martyn
• Format: Article
• Language: English
• Subjects: Alston Block; Areal geology; Armstrong, Andrew; Burtreeford Disturbance; Cary, John; England; Europe; faults; geologic maps; Geologists; Great Britain; historical documents; history; intrusions; mapping; maps, charts; Northumberland England; Phillips, John; Phillips, John (British geologist); River East Allen; sills; Smith, William; Smith, William (British geologist); Stublick Fault; United Kingdom; Western Europe; Whin Sill; Works
• ISSN: 0736-623X; 1944-6187
• DOI: 10.17704/1944-6187-35.1.99

Smith's geological map of Northumberland probably was the most challenging of his 21 county maps to complete. It combined at least two earlier sets of data together with additional fieldwork in 1821 by his nephew John Phillips. This account focuses on two extant pre-publication maps and relates them to the published version. The earliest is a Smith field map drawn onto an Andrew Armstrong base map dated 1769 and the other is a pre-publication map drawn by an unknown hand onto a John Cary 1821 base map, possibly for use by Phillips as a reference map during his 1821 field work. There were significant gaps in the compilation of field data into a final master map caused by misfortunes ranging from Smith's wife's deteriorating mental state, his debt problems, brief incarceration, and a devastating fire at the Cary print works. Advancing old age also encouraged Smith to increasingly draw on the assistance of John Phillips for the final Northumberland field work. This was Phillips' first important piece of solo field mapping and was carried out late in 1821. His itinerary was designed in liaison with Smith who was concurrently working in Cumbria. Unfortunately, Phillips' field reference map misinterpreted Smith's inland Whin Sill outcrops drawn on the 1769 Armstrong base map. Consequently, Phillips in 1821 did not recognise their significance and failed to include them in the 1824 published map. Nevertheless, Phillips did solve Smith's geological problems in the southwest of the county where the Hartley Burn (Midgeholme) coalfield appeared to be out of sequence along its unexposed southern margins. This was correctly interpreted as a major fault contact and was indicated by a dashed line on the 1824 published map. This is believed to be the first fault line to be drawn on any Smith map and fits closely to the northern master fault of the Alston Block now known as the Stublick Fault. Phillips also identified the northerly extension of the Burtreeford Disturbance into the area. This is also marked by a bold dashed north-south line along the valley of the River East Allen. A third (unnamed) fault-line with a northwest-southeast trend in the West Allen valley was identified on the basis of truncated mineralisation within deep mines in the High Chapel area.