Basin-scale architecture of deeply emplaced sill complexes: Jameson Land, East Greenland

Abstract

Igneous sills are common components in rifted sedimentary basins globally. Much work has focused on intrusions emplaced at relatively shallow palaeodepths (0 -1.5 km). However, owing to constraints of seismic reflection imaging and limited field exposures, intrusions emplaced at deeper palaeodepths (>1.5 km) within sedimentary basins are not as well understood in regard to their emplacement mechanisms and host-rock interactions. Results from a world-class, seismic-scale outcrop of intruded Jurassic sedimentary rocks in East Greenland are presented here. Igneous intrusions and their host rocks have been studied in the field and utilizing a 22 km long 'virtual outcrop' acquired using helicopter-mounted lidar. The results suggest that the geometries of the deeply emplaced sills (c. 3 km) are dominantly controlled by host-rock lithology, sedimentology and cementation state. Sills favour mudstones and even exploit centimetre-scale mudstone-draped dune-foresets in otherwise homogeneous sandstones. Sills in poorly cemented intervals show clear ductile structures, in contrast to sills in cemented units, which show only brittle emplacement structures. The studied host rock is remarkably undeformed despite intrusion. Volumetric expansion caused by the intrusions is almost exclusively accommodated by vertical jack-up of the overburden, on a 1:1 ratio, implying that intrusions may play a significant role in uplift of a basin if emplaced at deep basinal levels.

Mechanisms of overburden deformation associated with the emplacement of the Tulipan sill, mid-Norwegian margin

“…Thus, the depth of emplacement is estimated to be not deeper than 1.5-2 km. The saucer-shaped geometry of the Tulipan sill is a consequence of such a shallow emplacement depth (e.g., Planke et al, 2005;Galland et al, 2009;Eide et al, 2016). This corroborates the observation of other studies (e.g., Hansen et al, 2011;Magee et al, 2014;Eide et al, 2016) and modeling (Galland et al, 2009), in which sills show a more planar geometry with increasing depth of emplacement.…”

“…This estimate is in agreement with observations of other sills in the Møre and Vøring Basins (e.g., Berndt et al, 2000), as well as those found in outcrop analogs (Eide et al, 2016;Jerram and Bryan, 2017). Using this estimate of thickness and the aerial distribution of the Tulipan sill, its volume is between 1.4 and 13.2 km 3 .…”

Mechanical models to estimate the paleostress state from igneous intrusions

“…Notably, many field examples of sills and dikes exhibit near-parallel dilation vectors, regardless of the intrusion attitude (e.g. Hoek, 1991;Walker, 1993;Airoldi et al, 2011;Martinez-Poza et al, 2014;Muirhead et al, 2014;Eide et al, 2016;Walker et al, 2017). Intrusions that demonstrate shear offset of markers across their margins indicate that during emplacement the dilation vector was inclined from plane normal (Muirhead et al, 2014;Walker et al, 2017); this obliquity of opening can be characterised by the opening angle (Fig.…”

Igneous seismic geomorphology of buried lava fields and coastal escarpments on the Vøring volcanic rifted margin

“…More recently the use of 3D Lidar surveying along with high-resolution 3D photogrammetric methods has revolutionized field based 3D surface mapping allowing rapid high precision 3D models to be created with relative ease (e.g. Nelson et al, 2011;Stevenson et al, 2011;Eide et al, 2017).…”