Seismic interpretation of sill complexes in sedimentary basins

implications for the sub-sill imaging problem

Christian Haug Eide (Corresponding Author), Nick Schofield, Isabelle Lecomte, Simon J. Buckley, John A Howell

Research output: Contribution to journalArticle

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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 to 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 in this study shows that, because of the high impedance contrast between siliciclastic host-rock
and dolerites, very thin (1-5 m) intrusions should in principle be imaged in reflection-seismic data at 3 km depth. However, comparison with actual seismic data with well-data shows significant amounts of unimaged sill intrusions, and this is likely due to limited seismic resolution, overburden complexity, inadequate velocity-models, and interference between reflections from closely spaced sills and sill-splays. Significant improvements to sill imaging and interpretation could be made by better predicting occurrence and geometry of sill intrusions and including these in velocity models.
Original languageEnglish
Pages (from-to)193-209
Number of pages17
JournalJournal of the Geological Society
Volume175
Issue number2
Early online date1 Dec 2017
DOIs
Publication statusPublished - Mar 2018

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sill
sedimentary basin
seismic data
seismic reflection
geometry
synthetic seismogram
diabase
overburden
igneous rock
outcrop
rock
modeling

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Seismic interpretation of sill complexes in sedimentary basins : implications for the sub-sill imaging problem. / Eide, Christian Haug (Corresponding Author); Schofield, Nick; Lecomte, Isabelle; Buckley, Simon J. ; Howell, John A.

In: Journal of the Geological Society , Vol. 175, No. 2, 03.2018, p. 193-209.

Research output: Contribution to journalArticle

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title = "Seismic interpretation of sill complexes in sedimentary basins: implications for the sub-sill imaging problem",
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 to 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 byabundant 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 in this study shows that, because of the high impedance contrast between siliciclastic host-rockand dolerites, very thin (1-5 m) intrusions should in principle be imaged in reflection-seismic data at 3 km depth. However, comparison with actual seismic data with well-data shows significant amounts of unimaged sill intrusions, and this is likely due to limited seismic resolution, overburden complexity, inadequate velocity-models, and interference between reflections from closely spaced sills and sill-splays. Significant improvements to sill imaging and interpretation could be made by better predicting occurrence and geometry of sill intrusions and including these in velocity models.",
author = "Eide, {Christian Haug} and Nick Schofield and Isabelle Lecomte and Buckley, {Simon J.} and Howell, {John A}",
note = "Acknowledgements: We thank reviewers Craig Magee and Murray Hoggett for considerate and insightful reviews that considerably improved this manuscript. The LIDAR data were acquired by Julien Vallet and Samuel Pitiot of Helimap Systems. We acknowledge NORSAR for an academic licence of the seismic modelling software SeisRoX, which was used to generate synthetic seismograms in this study, and NORSAR-2D, which was used for analysis of seismic propagation through the overburden models. The virtual outcrop was visualized and interpreted using LIME (http://virtualoutcrop.com/lime). We also acknowledge Tore Aadland for writing invaluable scripts used for import of the outcrop models to seismic modelling software, and Gijs A. Henstra and Bj{\"o}rn Nyberg for assistance in the field. Funding: Funding for data acquisition was provided from the Research Council of Norway through the PETROMAKS project 193059 and the FORCE Safari project. Funding for data analysis and modelling was provided from PETROMAKS through the Trias North project (234152).",
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N2 - 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 to 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 byabundant 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 in this study shows that, because of the high impedance contrast between siliciclastic host-rockand dolerites, very thin (1-5 m) intrusions should in principle be imaged in reflection-seismic data at 3 km depth. However, comparison with actual seismic data with well-data shows significant amounts of unimaged sill intrusions, and this is likely due to limited seismic resolution, overburden complexity, inadequate velocity-models, and interference between reflections from closely spaced sills and sill-splays. Significant improvements to sill imaging and interpretation could be made by better predicting occurrence and geometry of sill intrusions and including these in velocity models.

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