Abstract:
This is a personal view of the seminal developments in our understanding of the nature of oceanic crust, and of ophiolites, that occurred in the 1960s and 1970s. This period followed the first measurements of the thickness and layering of the oceanic crust, using seismic refraction techniques, in the 1950s, and preceded the very detailed studies of oceanic basement, carried out within the context of the Ocean Drilling Program, and of ophiolites, notably in Cyprus and Oman, in the 1980s. During the 1960s and 1970s, I had the good fortune to work on these advances with Drummond Matthews, Harry Hess, Tuzo Wilson, Eldridge Moores, Jason Morgan, Ian Gass, and Joe Cann, among others. My own contribution related mainly to the constraints on the composition, formation and structure of oceanic crust that were provided by the interpretation of oceanic magnetic anomalies and the magnetic and paleomagnetic studies of the Troodos ophiolite of southern Cyprus. By the end of the 1970s, the essential nature of oceanic crust and ophiolites and their probable equivalence had been established, but it is only since then that the details of the variability of oceanic crust and the ways in which this might be related to the variability of ophiolites have become apparent.