Schiffer, Christian2; Jacobsen, B. H.2; Balling, N.2; Nielsen, S.B.2
1 Department of Geoscience, Science and Technology, Aarhus University2 Department of Geoscience, Science and Technology, Aarhus University
Subsequent to their formation the East Greenland and Scandinavian Caledonides formed a major coherent mountain range. The understanding of the European Caledonides therefore naturally involves also the East Greenland Caledonides. The present-day topography and crustal and upper mantle structure in East Greenland were influenced by an extensive geological evolution involving several geodynamical processes, including the closure of the Iapetus Ocean with continent-continent collision, subsequent gravitational collapse, extension and rifting. The passive margin development associated with the opening of the North Atlantic was furthermore spiced up by the pronounced localized anomalous volcanism around Iceland. Erosion shaped the today’s distinct geological structure and landscape, culminating in the Quaternary glaciations. The focus of this presentation is on the deep crustal and upper mantle evidence for the processes before and under the Caledonian orogeny. We performed a Receiver Function analysis of data from 11 seismological broadband stations forming the Ella-Øarray. This array, maintained by Aarhus University, covered an approximately 270 km long profile, spanning the East Greenland Caledonides from the Greenland Ice Sheet to the coast at about 73 N for a period of two years (2009-2011). The data reveal a clear eastward dipping lineament through the mantle lithosphere underneath the study area. The geophysical character as well as synthetic modelling is consistent with a 6-12 km thick, subducted slab of high velocity, eclogitized oceanic crust. We interpret this structure as a remnant of an early subduction and collisional event which pre-dates the main Scandian phase of orogeny with the collision of Baltica and Laurentia. This is a key evidence for the unravelling of the complexity of the closure of the Iapetus Ocean and the formation of the Caledonides.
East Greenland; Caledonides; Receiver Functions; Fossil Subduction; Seismology