Advances in modern structural geology: A special issue in honour of the life and work of John G. Ramsay

This special issue of Journal of Structural Geology is dedicated to Prof. John Graham Ramsay CBE (1931–2021), a founding member of the journal’s editorial board, and other leading publications in Structural Geology and Tectonics. Our foremost intention is to honour John Ramsay’s scientific legacy and the huge impact his fundamental work has had on the Geosciences (e.g. Ramsay, 1967), and which still resonates within the global Earth Science community (Lisle et al., 2020). John Ramsay pioneered Modern Structural Geology by laying the foundation for the geometric analysis and mathematical description of rock deformation based on observed structures (Ramsay, 1958; 1962a; b, 1967, 1974, 1980; Ramsay and Graham, 1970; Ramsay and Huber, 1983, 1987; Ramsay and Lisle, 2000). To this day we build on these concepts when studying the processes that deform rocks, their tectonic context, or when applying these approaches to geotechnical solutions and exploration of natural resources. His landmark textbook on “Folding and Fracturing of Rocks” (Ramsay, 1967) was published more than 50 years ago and has become the underlying theoretical framework that revolutionized our discipline. Over the years Structural Geology has evolved and new challenges have emerged, prompting the development of novel approaches and leading the discipline into its exciting future realm (e.g., Ramsay and Lisle, 2000; Bond and Lebit, 2020). In line with John Ramsay’s visionary and innovative spirit, this special issue reflects research at the forefront of Structural Geology and its associated disciplines, and includes traditional methods and approaches as well as new techniques and concepts. The quantification of rock deformation continues to be of pivotal importance in stress and strain analysis. In this context, we study the spatial and temporal evolution of rocks, their folding and fracturing in the widest sense and their response to the changing conditions during deformation. Following John Ramsay’s legacy, geological mapping, careful outcrop studies and thorough multi-scale analyses are critical for validating geological models and tectonic hypotheses. Equally critical are theoretical treatments, together with physical and numerical experiments focusing on defor- mation processes that result in natural structures and fabrics at various scales. This special issue on “Advances in Structural Geology” represents a collection of 33 papers offering a wide spectrum of topics ranging from classical structural approaches to new numerical and analytical technologies, which exemplify recent progress in Structural Geology. We broadly group the contributions into different themes; beginning with John Ramsay’s iconic work on shear zone analysis (Ramsay and Graham, 1970; Ramsay, 1980) where several papers provide new insights and kinematic interpretations of various tectonic domains. This section expands into transcurrent deformation systems, which are common in numerous tectonic terrains. The subsequent collection of papers focuses on using small-scale and mi- crostructures to track the deformation path of rocks, and to develop new approaches to quantify deformation. The next major section considers several contributions that build on John Ramsay’s seminal textbook on the fundamentals of folding and fracturing of rocks (Ramsay, 1967). These contri- butions primarily deal with theoretical and outcrop-scale structural analysis of kinematic systems. This includes numerical solutions to validate structural settings in nature. The last section focuses on applying modern structural geology to various salt tectonic scenarios, as well as geotechnical issues related to fractured reservoirs and subsurface gas storage. One of John G. Ramsay’s most significant contributions focuses on the analysis of shear zone geometries and the progressive development of associated structures. The simple shear concept has been expanded into more complex tectonic settings and explored in regional applications, combined with new techniques that define the thermo-mechanical evolution of shear zones at various scales.