Sedimentary and crustal structure from the Ellesmere Island and Greenland continental shelves onto the Lomonosov Ridge, Arctic Ocean

Abstract

On the northern passive margin of Ellesmere Island and Greenland, two long wide-angle seismic reflection/refraction (WAR) profiles and a short vertical incident reflection profile were acquired. The WAR seismic source was explosives and the receivers were vertical geophones placed on the sea ice. A 440 km long North-South profile that crossed the shelf, a bathymetric trough and onto the Lomonosov Ridge was completed. In addition, a 110 km long profile along the trough was completed. P-wave velocity models were created by forward and inverse modelling. On the shelf modelling indicates a 12 km deep sedimentary basin consisting of three layers with velocities of 2.1–2.2, 3.1–3.2 and 4.3–5.2 km s−1. Between the 3.1–3.2 km s−1 and 4.3–5.2 km s−1 layers there is a velocity discontinuity that dips seaward, consistent with a regional unconformity. The 4.3–5.2 km s−1 layer is interpreted to be Palaeozoic to Mesozoic age strata, based on local and regional geological constraints. Beneath these layers, velocities of 5.4–5.9 km s−1 are correlated with metasedimentary rocks that outcrop along the coast. These four layers continue from the shelf onto the Lomonosov Ridge. On the Ridge, the bathymetric contours define a plateau 220 km across. The plateau is a basement high, confirmed by short reflection profiles and the velocities of 5.9–6.5 km s−1. Radial magnetic anomalies emanate from the plateau indicating the volcanic nature of this feature. A lower crustal velocity of 6.2–6.7 km s−1, within the range identified on the Lomonosov Ridge near the Pole and typical of rifted continental crust, is interpreted along the entire line. The Moho, based on the WAR data, has significant relief from 17 to 27 km that is confirmed by gravity modelling and consistent with the regional tectonics. In the trough, Moho shallows eastward from a maximum depth of 19–16 km. No indication of oceanic crust was found in the bathymetric trough.