Tectonic slides in the Caledonides

Abstract

Summary Despite the continuing use of the term ‘tectonic slide’ in the Caledonian fold belt of Britain and Ireland for the past fifty years, the concept has found few advocates elsewhere. To many geologists outside the British Isles it remains a subject of some confusion. A review of the literature suggests that slides are a general term for faults which form in close association with syn-metamorphic regional deformation. They are often related to major folds although this is not a diagnostic feature. Neither is any movement sense implied in the term slide; thus, they may be thrusts, lags, oblique slip etc. Classically, these structures lie along and subparallel to the boundaries of major lithological units but transgress the stratigraphy on a larger scale. Structural analogies with the thrusts of the lower grade or non-metamorphic deformed cover sequences can often be seen in slides. However, they are more commonly and possibly fundamentally the result of differing responses to deformation of contrasting, adjacent lithologies in areas of higher strain and metamorphism.