Geophysical characterisation of the ocean–continent transition at magma-poor rifted margins

Abstract

Geophysical characterisation of the ocean-continent transition (OCT) at magma-poor riftedmargins has focused primarily on the determination of P wave velocities using wide-angleseismic techniques. Such experiments have shown that the OCT is heterogeneous, but thattypically velocities increase gradually with depth from ~5.0 km/s at top basement to ~8.0km/s at ~5 km deeper, without a large and abrupt Moho transition. The velocity variationwith depth is similar to that of old fracture zone crust, and appears to differ from that ofoceanic crust formed at ultra-slow spreading rates, though sampling of the latter is limited.Typically, the OCT is characterised by weakly lineated, low amplitude magnetic anomalies;the interpretation of these anomalies remains controversial. The oceanward limit of the OCTremains poorly defined on many margins