Seismic Interpretation of Sill-Complexes in Sedimentary Basins: The ‘Sub-Sill Imaging Problem’

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1144/jgs2017-096.

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Authors

Christian Haug Eide , Nick Schofield , Isabelle Lecomte, Simon Buckley, John A. Howell 

Abstract

Application of 3D-seismic reflection-data to igneous systems in sedimentary basins has led to a revolution in the understanding of mafic sill-complexes. However, there is considerable uncertainty on how geometries and architecture of sill complexes within the subsurface relates those imaged in seismic reflection-data. To provide constraints on how sill complexes in seismic data should be interpreted, we present synthetic seismograms generated from a seismic-scale (22x0.25 km) outcrop in East Greenland constrained by abundant field-data.
This study highlights how overlying igneous rocks adversely affect imaging of underlying intrusions and rocks by decreasing seismic amplitude, frequency and making steeply dipping features near-impossible to image. Furthermore, seismic modelling shows that because of the high impedance contrast between siliciclastic host rock and dolerites, thin (< 5m) intrusions should in principle be imaged at relatively high amplitudes. This is contrary to many published ‘rules of thumb’ for seismic detectability of sill intrusions. However, actual seismic data combined with well-data shows significant amounts of un-imaged sill intrusions, and this is likely due to limited resolution, overburden complexity, poor velocity-models, and interference between closely spaced sill-splays. Significant improvements could be made by better predicting occurrence and geometry of sill intrusions and including these in velocity models.

DOI

https://doi.org/10.31223/osf.io/jfs9x

Subjects

Earth Sciences, Geology, Geophysics and Seismology, Physical Sciences and Mathematics, Volcanology

Keywords

North Atlantic, Sills, seismic interpretation, igneous sill complexes, Jameson Land Suite, mafic sills, seismic modelling

Dates

Published: 2017-10-30 08:26

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License

Academic Free License (AFL) 3.0

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