Dynamic support by the Iceland Plume and its effect on the subsidence of the northern Atlantic margins

Abstract

Abstract A transect of drill sites across the East Greenland margin made by ODP Leg 152 provides important new data on the subsidence history of this margin, complementing earlier ODP and DSDP drill sites on the conjugate Hatton Bank, as well as the Vøring Plateau. Fluvial sediments recovered from under the basalts of the dipping reflector series indicate uplift and subaerial exposure of the margin prior to basalt eruption. The basaltic basement at Site 918, located oceanward of the continent-ocean transition, shows anomalously slow subsidence during the first 15–20 Ma after continental break-up, compared to normal ocean crust. Similar anomalous subsidence characterizes the early subsidence at DSDP Sites 552–554 on the Hatton Bank. Here however the anomaly is of lower magnitude and of shorter duration. At the Vøring Plateau dynamic support is apparent on the landward side of the continent—ocean transition but offshore the evidence for strong, long duration support is lacking. We interpret the subsidence results to reflect dynamic support of the North Atlantic rifted margins by the Iceland plume, with the greater support at the East Greenland sites reflecting their position closer to the plume centre during the initial post-rift period than those on the Hatton Bank or Vøring Plateau. The subsidence data are in accord with models of a large plume head of 1000 km radius but cannot resolve between models proposing arrival of a pre-existing plume into the area during the late Palaeocene, rather than the incubation of a new plume under the area at that time. The low degree of dynamic support seen at the Vøring Plateau and the marked difference between the support at the East Greenland drill sites versus those at Hatton Bank does not support the plume centre being at Kangerdlugssuaq at 55 Ma, but instead at a location further west, under the Greenland craton.