Aspects of the structure on the coast of the West Greenland volcanic province revealed in seismic data

Abstract

The coastal structure in central West Greenland is expressed by Palaeogene basalts which show pronounced seaward dip. Traced along strike the tilted basalts occur in two segments, separated by an area in which dips are low. Within these segments the lavas have been displaced by extensional faults with strike parallel to the strike of the lavas and dip and downthrow to the landward side. This structural pattern bears many similarities to regional structural features in volcanic rifted margins in other parts of the world, although in West Greenland the continent-ocean boundary is situated more than 100 km west of the coast. The structure has previously been studied onshore and has now been studied in high-resolution seismic data acquired both west of the coast and in the sounds between the Nuussuaq and Svartenhuk peninsulas. From the offshore data it can be seen that within the sections correlated with mid-Paleocene volcanic rocks onshore, the tilting of the lavas took place almost entirely after eruption, as there is little or no indication of any increase of dip towards the faults or of fan-shaped geometry in cross-section. However, southwest of Ubekendt Ejland and stratigraphically within Early Eocene lavas, dips can be seen to increase with depth in several fault blocks, indicating that tilting was active during eruption of these lavas. It is therefore concluded that tilting of the volcanic rocks in the coastal zone took place largely in the Eocene. This conclusion is corroborated by the following onshore evidence: Firstly, the angle of discordance between seaward-dipping Eocene lavas and the underlying tilted Paleocene lavas is small, where observed at all, so the mid-Paleocene lavas must owe their seaward dip largely to tilting during the Eocene. Secondly, Early Eocene ages have been obtained from sequentially tilted dykes onshore. This tilting and concomitant extensional faulting was contemporaneous with the second phase of seafloor spreading in the Labrador Sea which took place during the Eocene. The first phase of seafloor spreading in this sea took place between magnetochrons 27r and 24r and was not accompanied by significant rifting of lavas in central West Greenland. It can also be seen from the seismic data that the tilted lavas level out less than 25 km from the coast. West of this, the volcanics generally show very low dips and thin gradually towards the continent-ocean boundary.

Late Cretaceous-Cenozoic basin inversion and palaeostress fields in the North Atlantic-western Alpine-Tethys realm: Implications for intraplate tectonics

“…There is also some onshore evidence for reactivation, but timings are very poorly constrained in west Greenland and Labrador (Wilson et al, 2006;Peace et al, 2018a). Field mapping and seismic data from this part of the west Greenland margin onshore indicate inversion of faults following the end of major volcanism in the Palaeocene (Skaarup and Pulvertaft, 2007) and photogrammetric mapping of volcanic surfaces highlights an undulating morphology adjacent to major basin faults, implying post-Palaeocene inversion (Sørensen et al, 2017).…”

Lithostratigraphy, geology and geochemistry of the volcanic rocks of the Vaigat Formation on Disko and Nuussuaq, Paleocene of West Greenland

“…They divide the volcanic succession into a number of antithetic fault blocks in which the lavas dip 2-22°W, thus exposing the youngest parts of the succession in the westernmost blocks. The offshore continuation of the lava succession has been conjectural (Geoffroy et al 1998(Geoffroy et al , 1999(Geoffroy et al , 2001Chalmers et al 1999b), but recent geophysical work shows that the antithetic fault system does not continue offshore but rather has given rise to a monocline of limited width (Skaarup 2002;Skaarup & Pulvertaft 2007;Gregersen & Bidstrup 2008). According to refraction seismic data, Paleocene oceanic crust is situated 120 km west of Disko (Funck et al 2012;Oakey & Chalmers 2012;Fig.…”

Methodology for Evaluating the North Atlantic Igneous Province Reveals Multiple Hotspots at Breakup

“…A decrease to Δ T p ∼ 125°C at the top of the Maligat Formation is followed by stabilization during deposition of the Svartenhuk and Naqerloq Formations at 60–55 Ma (Figure 10b). However, a pronounced unconformity separates the Eocene Naqerloq Formation from the Paleocene Svartenhuk Formation (Larsen et al., 2015; Skaarup and Pulvertaft, 2007). Basalt accumulation rates are high in the pre‐breakup Vaigat Fm (62–61 Ma) at 2000m/Ma, reducing toward 1000 m/Ma in the Svartenhuk Fm.…”

“…Another problem is the upscaling of the outcrop model itself. Skaarup and Pulvertaft, (2007) suggested that the listric crustal‐scale normal faults in Geoffroy's (2005) model, are in fact smaller‐scale domino faults. Moreover, stretching models pay little attention to volcanic stratigraphy or the source of SDRs and require the need for an elusive footwall, residual central horst or C‐block (e.g., Geoffroy et al., 2015; Quirk et al., 2014).…”