Four seismic refraction velocity models integrated with 2-D gravity modelling outlinethe East Greenland continent-ocean transition zone (COT) between the Jan Mayen and Greenland fracture zones. The offshore margin structures are illustrated by regional transects and maps of basement and Moho depth as well as the thickness of the crystalline crust and the 7+ km/s lower crustal body. A correlation with the regional magnetic anomalies revealed constraints of the timing and involved pre- syn- and post break-up magmatism. Break-up propagation is proposed from north to south between 54 to 50 Ma. The delayed break-up in the southern part of the margin coincides with a large high velocity body beneath the COT, intruded transitional crust and concealed flood volcanism mixed with syn-rift sediments. Oceanic crustal thickness seaward of the COT decreases rapidly to normal thicknesses. The two northern transects show a clearly different picture of the margins structure. A strong velocity and density anomaly beneath Shannon Island can be related to the Shannon High. A basin filled with continental Devonian to Cretaceous sediments and with probably unresolved horsts and grabens down to 15 km was modelled eastwards. No high velocity lower crustal body or large scale intrusions were identified contrarily to the southern transects. The northern most profile located south of the Greenland Fracture Zone revealed even less crustal intrusions associated with break-up related magmatism. The crustal architectures give rise to variations in rifting processes with a possible transition near 75°N. If these rifting processes influenced the magmatism or a sequence of magmatic events formed the investigated crustal architecture is a matter of debate. Different scenarios will be discussed for their applicability, e.g. long term rifting and magmatism or mutli-phase emplacement of magma during North Atlantic and Jan Mayen break-up.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > MAR2-Palaeo Climate Mechanisms and Variability