Modern applications for basin-wide revision mapping in the Old Red Sandstone, Scotland

The Strathmore Basin is an extensive Silurian-Devonian basin which spans the entire width of Scotland. This basin has had a long and complex tectonic history, including periods of significant volcanic activity, faulting, basin folding, and several movements along the basin-bounding Highland Boundary Fault. Today, the basin is largely covered by substantial glacial deposits; bedrock exposure is limited.

Some areas of the basin were last mapped in the 1880’s (i.e., before aerial photography, and nearly a century before the theory of plate tectonics). Progressive mapping of adjacent map sheets up to the 1970’s has led to mismatches at sheet boundaries, significant inconsistencies in structural interpretation, and irregularities in stratigraphic relationships. Addressing these legacy issues in geological maps is critical for ensuring suitability for 21^st century applications; these data are used to inform the management of the regional aquifer within the Devonian sandstones, and for evaluation of potential geothermal energy resources.

A novel basin-wide approach has been taken to revise the geological mapping to improve map quality and consistency across the Strathmore Basin. This has involved a range of techniques, including digital terrane analysis, targeted field visits, the integration of published geochronological data, and the compilation of basin-wide datasets of over 4,000 structural measurements and more than 20,000 observation points from multiple BGS data sources. This approach has allowed for a new large-scale structural interpretation of the fold and fault systems, particularly related to the Highland Boundary Fault, as well as a new understanding of key stratigraphic markers and a more coherent representation of the geology across the basin. This approach highlights the value of using both modern and historic datasets, and crucially, revisiting targeted outcrops in the field.

As traditional survey styles become less affordable, and the need for seamless maps more acute, regional approaches provide an important methodology, helping to maximise the value of existing data and targeting areas for new data collection. Understanding these strengths and limitations is essential for the future of resurvey, especially in countries such as the UK with a long surveying history and high demand for accurate and consistent geological information to manage energy, water, and mineral resources.