Volcanic features of the North Rockall Trough: application of visualisation techniques on 3D seismic reflection data

Abstract

Understanding the volcanic processes operating during continental break-up is hampered by the subsequent burial of the majority of the volcanic pile beneath thick sedimentary sequences currently located in bathymetrically deep offshore regions. Although portions of these volcanic systems are currently exposed on land, a full understanding of the volcanic structure, the eruptive styles and their evolution is not possible as these localities have been partially eroded. Furthermore, as the onshore exposure represents a volumetrically minor part of the entire system, the documented eruptive styles may not be representative. The increasing availability of 3D seismic reflection data has the potential to significantly enhance our understanding of break-up related volcanism, as it allows direct access to detailed information from the buried volcanic succession. However, conventional seismic interpretation methodologies cannot determine lava flow morphologies, and as a result, eruptive styles and their evolution are still largely based on extrapolation from the accessible onshore outcrop data. New 3D seismic volume visualisation techniques allow the buried basalt morphologies to be examined for the first time in a manner similar to outcrop, aerial photographic or satellite-based observations. Applying this new approach for 3D seismic data to the North Rockall Trough, U.K. Atlantic margin, demonstrates that a range of volcanic features indicative of eruptive style can be determined. The data reveal a complex terrain containing lava flows originating from discrete volcanic centres, contemporaneous normal faults, linear fissures a few kilometres long, radial fissures and inflation ridges. Lava flow morphologies that are indicative of tube-fed inflated sheetflows, intracanyon flows and elongate subaerial flows that enter water downslope to produce a large hyaloclastite delta are observed.

Decoding sill emplacement and forced fold growth in the Exmouth Sub-basin, offshore northwest Australia: Implications for hydrocarbon exploration

“…However, we note that the seismic character and depth of the interval of interest is 163 comparable to that of the area studied by Magee et al (2013a) intrusive contact reflections will occur, producing a tuned reflection package, and the true sill 189 thickness will be uncertain (Smallwood and Maresh, 2002;Thomson, 2005;Magee et al, 190 2015;Planke et al 2015 The eastern limit of Horizon C is partly defined by a W-dipping major fault, whereas…”

Determining magma flow in sills, dykes and laccoliths and their implications for sill emplacement mechanisms

“…In addition, this approach provided some examples of feeder zones. These included a sill impinging on the base of another sill emplaced at a higher stratigraphic level (Thomson and Hutton 2004) and a number of bilaterally symmetrical sills radiating as spokes from a feeder zone for a contemporaneous volcanic centre (Thomson and Hutton 2004;Thomson 2005b). In both cases, the branching patterns and the positions of the proposed feeders were consistent and supported a laccolith style of emplacement.…”

Understanding the offshore flood basalt sequence using onshore volcanic facies analogues: an example from the Faroe–Shetland basin

“…In the NAIP, sill complexes have been successfully imaged in some of the 3D seismic data sets (e.g. Thomson, 2005) and where limited or no significant lava cover exists (e.g. Hansen, 2006).…”

“…In order to understand better the 3D distribution of the significant lava sequences offshore, flood basalt facies schemes and 3D mapping have been developed from seismic studies (e.g. Planke, Alvestad & Skogseid, 1999;Planke et al 2000Planke et al , 2005Thomson, 2005) and detailed field studies of onshore successions of flood basalts and their associated sediments (e.g. Jerram, Mountney & Stollhofen, 1999;Mountney et al 1999;Jerram, 2002;Single & Jerram, 2004).…”