S U M M A R YDeep seismic refraction data were gathered across the entire East Greenland rifted margin north of the Jan Mayen Fracture Zone between 72 • N and 75 • N in 2003. Investigations of the deep crustal structure of this continental margin provide constraints on the formation of the margin and its structural evolution during and after late Cretaceous-early Tertiary rifting and continental break-up. We present here the results along two profiles located in the prolongation of the Godthåb Gulf and the Kejser Franz Joseph Fjord. Regional P-wave velocity models were derived from forward traveltime modelling of land stations and ocean bottom hydrophone (OBH) recordings. For the first time, long deep seismic sounding transects off East Greenland provide a full insight into the crustal architecture of the transition from continental to oceanic crust. A mean result is the identification of voluminous magmatic underplating, which is wider and thicker than previously thought. P-wave velocities of the underplated material range between 7.1 and 7.4 km s −1 and the horizontal extents on the profiles are 225 and 190 km. The maximum thickness of the underplated material is 15-16 km. Furthermore, the P-wave velocity models reveal a 120-130 km wide continent-ocean transition zone (COT), based on an interpretation of the extent of Cretaceous syn-rift sediments mixed with basaltic intrusions and the lateral increase of velocities in the crustal layers. Excess magmatism must have been present during a long-term rifting process, accompanying the extension of the continental crust and giving rise to the voluminous magmatic underplating. A consequence of our interpretation of the seismic refraction data is a likely rift propagation in the Greenland Sea from north to south. Additionally, a comparison of P-wave velocity models of the East Greenland Margin and Vøring Margin reveals significantly asymmetric crustal architectures. The voluminous magmatic underplating and asymmetrical conjugate margins formations are considered as a mirror of complex pre-and syn-rift processes.

S U M M A R YSeismic velocities and the associated thicknesses of rifted and igneous crust provide key constraints on the rifting history, the differentiation between non-volcanic and volcanic rifted margins, the driving force of magmatism at volcanic margins, that is, active or passive upwelling and the temperature anomaly in the lithosphere. This paper presents two new wideangle seismic transects of the East Greenland margin and combines the velocity models with a compilation of 30-wide-angle seismic velocity models from several publications along the entire East Greenland margin. Compiled maps show the depth to basement, depth to Moho, crustal thickness and thickness of high velocity lower crust (HVLC; with velocities above 7.0 km s −1 ). First, we present two new wide-angle seismic transects, which contribute to the compilation at the northeast Greenland margin and over the oceanic crust between Shannon Island and the Greenland Fracture Zone. Velocity models, produced by ray tracing result in total traveltime rms-misfits of 100-120 milliseconds and χ 2 values of 3.7 and 2.3 for the northern and southern profiles with respect to the data quality and structural complexity. 2-D gravity modelling is used to verify the structural and lithologic constraints. The northernmost profile, AWI-20030200, reveals a magma starved break-up and a rapidly thinning oceanic crust until magnetic anomaly C21 (47.1 Ma). The southern seismic transect, AWI-20030300, exhibits a positive velocity anomaly associated with the Shannon High, and a basin of up to 15 km depth beneath flood basalts between Shannon Island and the continent-ocean boundary. Breakup is associated with minor crustal thickening and a rapidly decreasing thickness of oceanic crust out to anomaly C21. The continental region is proposed to be only sparsely penetrated by volcanism and not underplated by magmatic material at all compared to the vast amount of magmatism further south. Break-up is proposed to have occurred at the seaward boundaries of the continent-ocean transition zones at between ∼50 and ∼54 Ma, propagating from north to south based on a joint analysis incorporating transects from the Kejser Franz Joseph Fjord and Godthåb Gulf. Secondly, the variation of the HVLC along the East Greenland margin from 60 • to 77 • N and from transects of its conjugate margin shows inverted emplacement of prominent landward and seaward HVLC thickness portions from north to south in a distribution chart. The differences in the HVLC distribution are attributed to one or more of the following three models. In the first model it is inferred that a transfer zone/detachment acts as a barrier to northward magma flow. In the second model, underplating results in thicker and highly intruded lower crust with several small-scale feeder dykes that locally increase the lower crustal velocities. In the third model, a second magmatic event associated with the separation of the Jan Mayen microcontinent is considered. Lithosphericscale inhomogeneities might be responsible for the heterogene...

Vertical distribution of fecal pellets and their sedimentation were studied during May and June 1986 at a permanent station on the Voering Plateau in the Norwegian Sea. Pellets were collected with water bottles as well as with moored time-series sediment traps and free-floating traps. Fecal pellets were counted, their carbon content was calculated and their composition was analyzed by scanning electron microscopy. Over 90 O/O of all suspended and sedimented fecal pellets orig~nated from copepods. Dally loss of suspended pellets from the upper 250 m of the water column via sedimentation was approx. 1 % of fecal pellet standing stock. Between 10 and 90 % of total sedimented material was attributable to these pellets; foraminifers and tintinnids accounted for the rest. It is suggested that most of the copepod pellets were broken down in the water column and/or were reingested (coprophagy). The chief constituent of both suspended and sedimented pellets was amorphous, hyalin material, in which small diatoms, coccol~thophores and coccoliths were occasionally found; large diatoms or fragments were rare. Microflagellates, which were the main autotrophs, could not be recognized in the pellets. Thus, sedimented material does not necessarily reflect species composition and abundance of phytoplankton of the upper water layers.

The separation of Northeast Greenland and Svalbard was achieved by large strike slip movements in Cenozoic times. Evidence for these movements can be found onshore both on North Greenland and Svalbard. However, the role of the Yermak Plateau in this process is quite speculative. New multichannel seismic (10 km spacing) and aeromagnetic data (7.5 km spacing) across the north‐western part of the plateau show that the acoustic basement has a similar strike direction to that of the geological units onshore Svalbard. A prominent fault zone separates these most likely continental structures in the west from a more N‐S extended transitional crustal block in the eastern part of the plateau. This part of the plateau is characterized by strong magnetic anomalies at least indicating highly intruded and stretched continental or even oceanic crust. However, the seismic data show that the plateau‐like bathymetry is quite young. During most of its Cenozoic history the Yermak Plateau had a rough topography, similar to the topography onshore Svalbard. Thus, the paleo‐bathymetry might have played an important role for the water exchange between the Arctic Ocean and the North Atlantic prior to the opening of the Fram Strait, which is today the main pathway for the deep‐water masses.

S U M M A R YSeismic investigations along East Greenland's Fjord Region completed during the last decade provide fundamental insights into the region's crustal structure and tectonic history. A summary of models along a transect through the Kejser Franz Joseph Fjord provides a view from the Precambrian Shield to the Eocene oceanic crust. We conclude that a change of rifting geometry from an upper-to a lower-plate-style margin occurred in early Mesozoic times and formed the >350-km-wide rift zone. Despite the demonstrated asymmetry of the northeast Greenland and conjugate Vøring margins, the change of rift geometries and the direction of rift jumps remain debatable. A combined model for productivity and duration of magmatism is proposed for the northeast Greenland fjord region. We suggest that magmatism started slowly at 58.8 ± 3.6 Ma with a production rate of 1.5 × 10 −4 km 3 km −1 a −1 , which is similar to the productivity of onshore upper and lower lava sequences on the Geikie Plateau. A peak of 9.4 × 10 −4 km 3 km −1 a −1 for 0.5 Myr, and a subsequent productivity of 4.4 ± 0.3 × 10 −4 km 3 km −1 a −1 for 2.5 Myr between 53.3 and 50.8 Ma, produced the majority of melt, but break-up did not occur immediately afterwards. Continuous production of melt, similar to the rate of ocean spreading until C22 (∼50 Ma), contributed to massive magmatic underplating until eventual break-up at 50 Ma. The volumes and production rates show similarities to those obtained from a profile off the southeast Greenland margin but with a major difference in a smaller regional spatial extent.