Christian Eide

Title: Seismic-scale architecture of deep-seated igneous intrusions in a sedimentary basin: Jameson Land, East Greenland

Abstract: Igneous sills are common components in rifted sedimentary basins globally. Much work has focussed on intrusions emplaced at relatively shallow paleodepths (0-1.5 km). However, due to constraints of reflection-seismic imaging and limited field-exposures, intrusions emplaced at deeper paleodepths (1.5-4 km) within sedimentary basins are as not 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. Volcanic intrusions and host-rock have been studied in the field and utilising a 22 km long “virtual outcrop” acquired using helicopter-mounted lidar. The results show how the geometry of deeply emplaced (c. 3 km) sills are controlled by host-rock lithology, sedimentology and cementation state. Sills exploit even small mudstone horizons, even exploiting mudstone-draped dune foreset in otherwise homogeneous sandstones. Sills in poorly cemented intervals show clear ductile structures, in contrast to sills in cemented units which show brittle emplacement-structures. The host-rock is remarkably undeformed despite intrusion. Volumetric expansion caused by the intrusions is almost exclusively accommodated by vertical jack-up of large host-rock blocks, on a 1:1 ratio, implying that intrusions may play a significant role in uplift of a basin if emplaced at deep basinal levels.