In 1888, inspired by fieldwork in what has become known as the Moine Thrust Belt, NW Scotland, Henry Cadell conducted a pioneering series of analogue deformation experiments to investigate structural evolution of fold and thrust belts. Some experiments showed that imbricate thrusts build up thrust wedges of variable form, without requiring precursor folding. Others demonstrated a variety of fold-thrust structures and how heterogeneities in basement can localise thrust structures. These experiments are described here and used to draw lessons in how analogue deformation experiments are used to inform the interpretation of fold-thrust structures. Early adopters used Cadell’s results as guides to structural styles when constructing cross-sections in thrust belts. His models and the host of others created since, serve to illustrate part of the range of structural geometries in thrust belts. But, as with much subsequent work, Cadell’s use of a deformation apparatus, with a fixed basal slip surface, biases perceptions of fold-thrust belts to be necessarily “thin-skinned” (experimental design bias) and can simply reinforce established interpretations of natural systems (confirmation bias). So analogue deformation experiments may be unreliable guides to the deterministic interpretations of specific fold-thrust structures in the sub-surface of the real world.
The Fold-Thrust Research Group has been funded by InterOil, Santos, OilSearch and NAGRA. The original compilation of Cadell’s researches was part of an outreach programme funded by BP.
RWHB is indebted to the late John Mendum for arranging access to Cadell’s notebooks and his field maps that were lodged in the then offices of the British Geological Survey in Murchison House, Edinburgh. This formed part of a collaboration with BGS and the development of the “Assynt’s Geology” website in the early 2000s. Many of the images from Cadell’s notebooks, including his experimental results, were part of this site. Regrettably it has not been maintained and is no longer accessible. Rectifying this loss of resource forms the motivation for this contribution. We thank Juergen Adam and an anonymous referee for construct reviews, together with James Hammerstein for shepherding the manuscript through the editing process, although of course the views expressed in this paper remain the responsibility of the authors alone.
- Moine Thrust belt
- analogue experiments
- interpretation uncertainty
- cognitive bias