Continent Ocean Boundaries in the North Atlantic: An Overview

The concept of a distinct continent-ocean boundary has been intensely challenged as a wealth of geological and geophysical data has been collected along passive margins in the last decade. Increasing new evidence points out that a sharp transition between continental and oceanic crust is rather an exception than a rule, and a continental-oceanic transition zone is proposed instead. However, the analysis of multidisciplinary data sets does not always lead to the same answer. Different interpretations of the same datasets led to competing hypotheses for the opening and tectonic evolution of the North Atlantic and Labrador Sea/Baffin Bay oceanic basins. The location of the ocean-continent transition zone is of particular relevance to UNCLOS article 76 on the legal continental shelf because it may be used as evidence to the contrary in positioning the foot of the continental slope, and as such enlarge a legal shelf claim. We re-examine the interpretation of continent-ocean boundaries or continent-ocean transition zones using up-to-date geophysical data and integrate it with a quantitative model of seafloor spreading in the North Atlantic. The opening of oceanic basins in the Arctic regions is also merged with the new kinematic model and various scenarios are examined with respect to their implications on the North Atlantic and Arctic continental margins. This overview of the tectonic evolution of the North Atlantic and Arctic is used to highlight regional problems and suggest data collection in key areas for better understanding of continental margin formation. It may well be that UNCLOS article 76 provides an opportunity to collect such data.