Geophysics and Remote Sensing
Igneous sheet intrusions such as sills, dikes, and laccoliths are abundant in volcanic basins. Mafic intrusions are characterized by highP-wave seismic velocities in the range from 5.0 to 7.0 km/s. Velocity aureoles with a thickness comparable to the sill intrusion are commonly identified on sonic log data above and below the intrusions. Sills as thin as 10 m may be detected by conventional seismic reflection data, whereas sills with a thickness above about 40 m are resolvable. Offset-dependent tuning of sill reflections is expected due to the high velocity of the intrusions. Deep sills are difficult to image by reflection methods but can be identified from wide-angle seismic data. Sill reflections are interpreted based on characteristic features such as their high amplitudes and saucer-shaped geometries. Sill complexes are further well-suited for 3D visualization techniques. Potential field and electromagnetic data may improve the reliability of the igneous intrusion interpretation; however such data have poor resolution if sills are buried below more than a few kilometers of sediments. Andesitic and felsic intrusions and laccoliths are less abundant than sills in volcanic basins, and few well-documented geophysical interpretation studies of such intrusions or dykes are published.
Special thanks to Audun Groth, Statoil, and VoxelVision for seismic visualization. Seismic data were kindly provided by TGS and EM data by EMGS. This work was partly supported by the Research Council of Norway through its Centres of Excellence funding scheme, project number 223272.
- Chevallier L, Woodford A (1999) Morpho-tectonics and mechanism of emplacement of the dolerite rings and sills of the western Karoo, South Africa. S Afr J Geol 102:43–54Google Scholar
- Evenchick CA, Embry AF (2012) Geology, Ellef Rignes Island north Nunavut: Map 86 (preliminary). In: Canadian geoscience. Geological Survey of CanadaGoogle Scholar
- Planke S, Cambray H (1998) Seismic properties of flood basalts from hole 917A downhole data, Southeast Greenland Volcanic Margin. Proc ODP Sci Results 152:453–462Google Scholar
- Planke S, Myklebust R (1999) Når seismikken kommer til kort. GEO, Trondheim 10:20–22Google Scholar
- Planke S, Rasmussen T, Rey S et al (2005) Seismic characteristics and distribution of volcanic intrusions and hydrothermal vent complexes in the Vøring and Møre basins. In: Geological Society, London, petroleum geology conference series. Geological Society of London, pp 833–844CrossRefGoogle Scholar
- Schofield A, Totterdell JM (2008) Distribution, timing and origin of magmatism in the Bight and Eucla basins. In: Geoscience Australia, p 19Google Scholar
- Skogseid J, Eldholm O (1989) Vøring Plateau continental margin: seismic interpretation, stratigraphy and vertical movements. Proc Ocean Drill Program Sci Results 104:993–1030Google Scholar
- Skogly OP (1998) Seismic characterization and emplacement of intrusives in the Vøring Basin. Cand Scient thesis, Department of Geology, University of OsloGoogle Scholar
- Smallwood J, Harding A (2009) New seismic imaging methods, dating, intrusion style and effects of sills: a drilled example from the Faroe-Shetland basin. In: Varming T, Ziska H (eds) Second Faroe Islands exploration conference. Sindri–Jardfeingi, Torshavn, Faroe Islands, pp 104–123Google Scholar