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. Supplementary materials: Uninterpreted versions of Figures 7, 8 and 11 are available at http://doi.org/10.6084/m9.figshare.c.3281882
Highlights
IntroductionGeological history of the Jameson Land BasinDuring the Devonian a series of north–south-trending extensional basins formed between present-day Norway and Greenland as a result of post-Caledonian rifting (Surlyk 2003)
Geological history of the Jameson Land BasinDuring the Devonian a series of north–south-trending extensional basins formed between present-day Norway and Greenland as a result of post-Caledonian rifting (Surlyk 2003)
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
Summary
Geological history of the Jameson Land BasinDuring the Devonian a series of north–south-trending extensional basins formed between present-day Norway and Greenland as a result of post-Caledonian rifting (Surlyk 2003). Relative sea-level rise in the latest Pliensbachian led to marine flooding of the basin and deposition of the Neill Klinter Group in a mainly tide-influenced, shallow-marine, structurally controlled embayment (Dam & Surlyk 1998; Eide et al 2016; Fig. 1a). The Neill Klinter Group is time-equivalent and analogous to the prolific reservoir rocks on the conjugate Halten Terrace offshore Norway (Martinius et al 2001; Ichaso & Dalrymple 2014), and was deposited in a minor sub-basin in the narrow, tide-dominated seaway that occupied the rifted continental crust between present-day Norway and Greenland (Gjelberg et al 1987; Fig. 1a).
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