Opening the Arctic Ocean: objective plate reconstructions in a data vacuum

The Arctic Ocean is one of the least known, and consequently least understood, oceanic regions on the planet. It contains three deep-water oceanic basins (the Eurasia, Makarov and Canada basins), with each basin separated from its neighbour by a submarine ridge. Understanding the nature of these ridges is crucial to understanding the tectonic evolution of the oceanic basins that they separate. The Lomonosov Ridge, a linear fragment of continental crust that was originally part of the Barents/Kara shelf margin, separates the Eurasia Basin from the Makarov Basin. The Alpha-Mendeleev Ridge, the origin of which has provoked considerable debate, separates the Makarov Basin from the Canada Basin.

Only in the Eurasia Basin is the opening history well constrained by a clear pattern of magnetic anomalies: the basin began to open in Paleocene time as a northward continuation of the North Atlantic spreading system, and spreading continues today on the ultraslow Arctic mid-ocean ridge. In contrast, the evolution of the Canada and Makarov oceanic basins is much less clear, largely because magnetic anomaly patterns are ambiguous, and other data that could constrain the nature of the crust or the timing of events are sparse, and their significance uncertain. The identification of a buried extinct spreading centre in gravity datasets, the presence of some subparallel magnetic anomalies, and stratigraphic evidence from the adjacent margins suggest that the southern Canada Basin probably opened by counter-clockwise rotation of Arctic Alaska away from the Canadian Arctic margin during Cretaceous time. However, the evolution of the central Arctic Ocean (comprising the northern Canada Basin, Makarov Basin, and the Alpha-Mendeleev Ridge that separates them) remains the subject of intense debate, and markedly contrasting interpretations.

The purpose of this review is to highlight some of the uncertainties and contradictions in current reconstruction models, and to demonstrate how regional tectonostratigraphic knowledge and the use of analogues may offer new insights into tectonic evolution of the Arctic Ocean. In particular, it will be demonstrated how recent advances in the understanding of microcontinent formation may provide an additional source of information with which to interpret the Lomonosov Ridge and the adjacent Makarov Basin.