iSIMM released abstracts

The iSIMM released abstracts area contains abstracts for meetings, presentations and posters which are available for public release. The abstracts will previously have been available on restricted access through the Abstracts section of the Partners' area.

Cambridge University workshop-conference Sub-basalt imaging: exploiting the full wavefield, 9-11th April 2002. Link to conference web-site.

A poster was presented at this meeting which gave an overview of the iSIMM project.
 
integrated Seismic Imaging and Modelling of Margins: an Overview - Lunnon et al
This abstract outlines a poster presentation of the project "integrated Seismic Imaging and Modelling of Margins" (iSIMM), a joint academic and industry collaboration supported by the Natural Environment Research Council and the Department of Trade and Industry under the NERC Ocean Margins Link programme. iSIMM seeks to model the evolution of magmatic margins and their basins using seismic imaging with integrated towed streamer and ocean bottom seismometer (OBS) data. This poster will describe the goals of the project and the plans for addressing those goals which will involve the acquisition of new data in the summer of 2002.
continued .... (80KB)

In addition Phil Christie presented a related talk about the Lopra borehole in the Faeroes.
 
Borehole Seismic Results From the Lopra Deepening Project - Christie et al
Extruded basalt flows overlying sedimentary sequences present a challenge to hydrocarbon exploration using reflection seismic. The Lopra re-entry well on the Faroe Island of Suðuroy allowed us to study the seismic characteristics of a thick sequence of basalt flows from well logs and borehole seismic recordings. Data acquired during the deepening operation in 1996 are presented, discussed and modelled in this paper. continued .... (33KB)

Geological Society conference on Frontier Exploration of Volcanic Continental Margins, 17-18th September 2002. Link to conference web-site.

Two poster presentations were made at this conference.
 
integrated Seismic Imaging and Modelling of Margins - the towed streamer surveys - Lunnon et al
This abstract outlines one of a two-part poster presentation describing the iSIMM project. iSIMM seeks to model the evolution of magmatic margins and their basins using seismic imaging with integrated towed streamer and ocean bottom seismometer (OBS) data. This poster will focus on the towed streamer data. continued .... (25KB)

integrated Seismic Imaging and Modelling of Margins - the OBS Surveys - Roberts, A.W. et al
This abstract outlines one of a two-part poster presentation describing the four year iSIMM project. iSIMM seeks to model the evolution of magmatic margins and their associated basins, using seismic imaging which integrates towed streamer and ocean bottom seismometer (OBS) data. This poster focuses on the OBS data. continued .... (37KB)

AGU annual meeting, San Francisco, 6-10th December 2002

A poster summarizing the iSIMM project was presented at this conference.
 
iSIMM (Integrated Seismic Imaging and Modelling of Margins):
Seismic Acquisition on the Faroes Shelf, Hatton Bank and adjacent Continental Margins
White, R.S. et al
The iSIMM project is using state-of-the art seismic techniques with long-offset and wide-angle data, to image the crust formed on volcanic continental margins in parallel with developing and testing new quantitative models of rifted margin formation, incorporating heterogeneous stretching, the effects of melt generation and emplacement and varying thermal anomalies in the mantle. During June-July 2002, we used RRS Discovery to acquire wide angle and normal incidence seismic data on the Faroes Shelf and adjacent continental margin, Hatton-Rockall Basin, Hatton Bank and the adjacent oceanic crust using OBS and MCS. In August 2002, WesternGeco’s Topaz used three single-sensor, Q-Marine streamers, 12km plus two 4km, to overshoot the wide-angle profiles on the Faroes Shelf and adjacent continental margin.
continued ....

Seismix2003

The 10th International Symposium on deep seismic profiling of the continents and their margins
Taupo, New Zealand, 6-10th January 2003
 
A poster summarizing the iSIMM project was presented at this conference.
Link to conference web-site
 
iSIMM (integrated Seismic Imaging and Modelling of Margins):
The North Atlantic volcanic continental margin
White, R.S. et al
The iSIMM project is investigating the structure of North Atlantic rifted continental margins using state-of-the art seismic data recorded in summer 2002, integrated with new models of rifted margin formation incorporating heterogeneous stretching, the effects of melt generation and emplacement and varying thermal anomalies in the mantle
continued ....

EGS-AGU-EUG Joint Assembly, Nice, France, 06 - 11 April 2003

Three abstracts covering the iSIMM project were submitted to this conference:
 
Influence of the iceland mantle plume on north atlantic continental margins -
a talk by White et al
 
Crustal structure from the Faroes shelf to the Norwegian basin -
a poster by Roberts et al
 
Modelling sea floor spreading initiation and rifted continental margin formation -
a poster by Tymms et al
 
Each of the abstracts is available below:

In addition to the iSIMM talks and posters one additional talk, on the iSIMM continental margins theme but of separate origin, was given as a keynote presentation at the conference. The abstract is available below.
 
Timing of depth dependent stretching on the Lofoten continental margin: pre-breakup or post-breakup?
Kusznir, Hunsdale & Roberts
Depth-dependent stretching has been observed at both non-volcanic and volcanic rifted continental margins (Driscoll & Karner 1998, Davis & Kusznir 2003). Stretching estimates, independently determined from upper crustal faulting, whole crustal thinning and post-rift lithosphere thermal subsidence, show that extension increases with depth within ~ 100 km of the COB such that whole-crustal and whole-lithosphere extension is significantly greater than upper-crustal extension. ... continued

EAGE Conference, Stavanger, Norway, 2nd - 5th June 2003

A highly-extended abstract / short-paper was submitted to this conference, with an option to develop the text into a full paper once the conference has taken place. The extended abstract, with illustrations is available as a PDF via the link below.
 
An evaluation of peak and bubble tuning in sub-basalt imaging: modelling and results
Lunnon, Z., Christie, P.F. & White, R.S.
Summary: As part of the iSIMM project (White et al. 2002), a 6,360 in3 airgun source array was used to shoot twice a deep seismic profile into a 380 km array of Ocean Bottom Seismometers (OBS) east of the Faroe Islands. The first pass used peak tuning, and the second used bubble tuning, with other source parameters constant. The objective was to deliver low frequency energy for deep, long-offset, sub-basalt penetration. The results suggest that towing large guns deep is more important than the tuning method. However, for the gun configuration used, the bubbletuned data are more compact, less reverberant and easier to pick.
continued ....

6th Petroleum Geology Conference: North West Europe & Global Perspectives

London, 7th-9th October 2003
 
Five abstracts covering the iSIMM project were submitted to this conference:
 
Rifting and magmatism on the North Atlantic continental margins -
a talk by White et al
 
Mantle Plume Temperature Variations Immediately Following Continental Breakup of the Northern North Atlantic -
a poster by Parkin et al
 
Investigating continental stretching, underplating and deep crustal structure of the Hatton-Rockall Basin and adjacent continental margin -
a poster by Smith et al
 
Mapping crustal thickness and stretching on the NW European Atlantic Margin using satellite altimetry gravity data -
a poster by Hurst et al
 
Modelling the initiation of sea floor spreading and formation of rifted continental margins -
a poster by Tymms et al
 
Each of the abstracts is available below:

At the conference itself limited space resulted in the four poster abstracts becoming consolidated into two posters displayed.
6th PGC poster 1 - Kusznir et al - Model development and testing of rifted continental margin formation
6th PGC poster 2 - Smith et al - Structure of the Hatton Basin and adjacent continental margin

In addition to the iSIMM talks and posters two additional talks, on the iSIMM continental margins theme but of separate origin, were given at the conference. The abstracts are available below.
 
Timing and magnitude of depth-dependent lithosphere stretching on the Lofoten continental margin: implications for subsidence and hydrocarbon maturation at volcanic rifted margins
Kusznir, Hunsdale & Roberts
Flexural backstripping and forward structural-and-stratigraphic modelling show that depth-dependent lithosphere stretching occurs on the outer part of the Norwegian rifted margin. Subsidence analysis on the Lofoten segment of the margin shows substantial thinning of the continental lithosphere within 100 km of the COB at continental breakup time (at approx. 54 Ma), while the upper crust shows no significant faulting and extension at breakup or immediately preceding breakup in the Palaeocene. ... continued
 
Structural development and palaeobathymetry at the Norwegian Atlantic margin:
revealed by 3D flexural-backstripping
Roberts et al
The technique of 3D-flexural backstripping has been used to derive a sequence of map restorations, back to the Base Cretaceous, for a major segment of the Norwegian Atlantic margin. The restorations cover the full extent of the Møre and Vøring Basins, a margin segment over 600km in length and 200-300km in width. The map restorations depict both surface palaeobathymetry and subsurface palaeostructure. ... continued

AGU annual meeting, San Francisco, 8-12th December 2003

Two abstracts covering basin-modelling aspects of the iSIMM project were submitted to this conference:
 
North Atlantic Rifted Margin Crustal Thickness and Crustal Thinning from Satellite Gravity Data -
a poster by Hurst et al
Crustal thickness has been derived from satellite gravity data for the North Atlantic between 50 and 70 degrees N in order to determine rifted margin crustal thinning. Satellite derived gravity anomaly data (Smith & Sandwell 1997) and bathymetry data (Gebco 2003) are used to derive the mantle residual gravity anomaly which is then inverted to give Moho depth. continued ...
 
Modelling Sea Floor Spreading Initiation and Depth Dependent Stretching at Rifted Continental Marginss -
a poster by Kusznir & Tymms
Depth dependent stretching, in which upper crustal extension is much less than that of the lower crust and lithospheric mantle, has been observed at both non-volcanic and volcanic margins and is not predicted by existing quantitative models of rifted margin formation which are usually based on intra-continental rift models subjected to very large stretching factors. New conceptual and quantitative models of rifted margin formation are required. continued ...
 
Each of the abstracts is available below:

EGU 1st General Assembly, Nice, 25-30th April 2004

Two abstracts covering basin-modelling aspects of the iSIMM project were submitted to this conference:
 
Modelling depth-dependent lithosphere stretching at rifted continental margins -
Kusznir & Tymms
Depth dependent stretching, in which upper crustal extension is much less than that of the lower crust and lithospheric mantle, has been observed at both non-volcanic and volcanic margins, however it is not predicted by existing quantitative models of rifted margin formation which are usually based on intra-continental rift models subjected to very large stretching factors. Observations suggest that the main thinning of rifted margin lithosphere occurs during early sea-floor spreading rather than during pre-breakup rifting. continued ...
 
Crustal thickness from satellite gravity data incorporating a lithosphere thermal correction: application to north atlantic rifted margins -
a poster by Kusznir, Hurst & White
Crustal thickness has been derived from satellite gravity data for the North Atlantic between 50 and 70 degrees N in order to determine rifted margin crustal thickness. Satellite derived gravity anomaly data (Smith & Sandwell 1997) and bathymetry data (Gebco 2003) are used to derive the mantle residual gravity anomaly which is inverted in 3D in the spectral domain to give Moho depth. continued ...
 
Each of the abstracts is available below:

 
In addition, Craig Parkin delivered a paper at this conference discussing aspects of the Hatton/Rockall iSIMM seismic programme and initial results:
 
Mantle plume temperature variations immediately following continental breakup of the northern North Atlantic
Parkin, White, Kusznir & Spitzer
The amount of melt generated by mantle decompression beneath an oceanic spreading centre and hence the oceanic crustal thickness is controlled primarily by the temperature of the mantle. By measuring the thickness of the oceanic crust formed immediately after breakup of the northern North Atlantic we are able to deduce the elevated mantle temperatures caused by the presence of the Iceland Mantle Plume. Crustal thickness variations are caused by temporal variations in the mantle plume temperature: at the present Reykjanes Ridge spreading centre the plume temperature pulses on a 3-5 Myr timescale with temperature variations of c.30K. continued ...

CGU-AGU-SEG-EEGS Joint Assembly, Montreal, 17-21st May 2004

Four abstracts covering basin-modelling aspects of the iSIMM project were submitted to this conference:
 
Modelling sea-floor spreading initiation and rifted continental margin formation: does depth dependent stretching occur pre- or syn-breakup? -
Kusznir & Karner
Depth dependent stretching, in which upper continental crustal extension is much less than that of the lower crust and lithospheric mantle, is a characteristic of both non-volcanic and volcanic rifted margins. A key question is whether depth dependent stretching of rifted margin lithosphere occurs during the initiation of sea-floor spreading or during pre-breakup rifting. A kinematic fluid-flow model of sea-floor spreading initiation has been developed to determine the concomitant distribution and amplitude of rifted continental margin lithosphere thinning and thermal evolution. continued ...
 
An inverse method to derive the kinematic history of rifted margin formation using a new model of sea floor spreading initiation -
Healy & Kusznir
Recent discoveries of depth-dependent stretching and mantle exhumation at rifted continental margins require new models of rifted continental margin formation. A two-dimensional coupled fluid mechanics/thermal kinematic model of sea-floor spreading initiation has been developed to predict the deformational and thermal evolution of continental rifted margins through time. continued ...
 
Predicting rifted continental margin subsidence history from satellite gravity derived crustal thinning: application to north atlantic margins
Hurst, Kusznir, Roberts & White
3D spectral inversion of satellite derived gravity anomaly data (Smith and Sandwell 1997) and bathymetry data (Gebco 2003) has been used to determine oceanic and continental margin crustal thickness for the North Atlantic between 50 and 70 degrees N. The inverse technique incorporates a correction for the large negative thermal gravity anomaly present in the oceanic and stretched continental lithosphere. continued ...
 
Mapping variations in oceanic and continental crustal thickness using satellite gravity data on the newfoundland rifted margin
Shillington, Kusznir & Holbrook
Crustal thickness has been derived from satellite gravity data for the Newfoundland continental margin between 40 and 50 degrees N using a new method incorporating a lithosphere thermal gravity anomaly correction. Satellite derived gravity anomaly data (Smith & Sandwell 1997) and bathymetry data (Gebco 2003) are used to derive the mantle residual gravity anomaly which is inverted in the 3D spectral domain to give Moho depth. continued ...
 
Each of the abstracts is available below:

Faroes Exploration Conference, Tórshavn, May 2004.

Imaging through igneous rocks on the Faroese Shelf
White & iSIMM
Massive magmatism occurred on the North Atlantic margins when the continents broke apart in the presence of the Iceland mantle plume. The magmatism resulted primarily from interaction between the Iceland mantle plume and the rifting continents. The igneous rocks were emplaced as extrusive lava flows, as sills and as intrusions in the lower crust. I discuss the challenges they pose to seismic imaging, and the advances we have made in imaging through the basalts and into the underplated lower crust. I show results from two recent seismic experiments undertaken across the Faroes Shelf and continental margin: continued ...

Petex 2004, conference and exhibition, London, November 2004 - Keynote address

Imaging Through Igneous Rock on the Faroese Shelf
White & iSIMM
Massive magmatism occurred on the North Atlantic margins when the continents broke apart in the presence of the Iceland mantle plume. The magmatism resulted primarily from interaction between the Iceland mantle plume and the rifting continents. The igneous rocks were emplaced as extrusive lava flows, as sills and as intrusions in the lower crust. I discuss the challenges they pose to seismic imaging, and the advances we have made in imaging through the basalts and into the underplated lower crust. I show results from two recent seismic experiments undertaken across the Faroes Shelf and continental margin:

NSF Intermargins workshop, Pontresina, Swiss Alps, July 2004

Crustal Architecture And Depth-Dependent Lithosphere Stretching Of The Northern Vøring And Lofoten Segments Of The Norwegian Margin: Along Strike Variation Across The Bivrost Transfer System extended abstract
Tsikalas, Kusznir & Faleide
The mid-Norway margin in NE Atlantic with its increasingly extensive database provides a natural laboratory to exemplify the integrated approach between observations and structural and stratigraphic modelling iteration in order to study continental breakup and fundamental volcanic rifted margin processes in time and space. In particular, recent subsidence analysis studies on the northern Vøring and Lofoten margin segments combined with all available seismic reflection and refraction data, and potential field modelling, clearly reveal distinct differences in crustal and lithospheric architecture between the two segments: continued ...

Pushing the Margins, Ocean Margins Link workshop, DTI London, November 2004

All of the main research groups in the OML program were represented at this meeting and the agenda is included below. Two presentations summarizing the iSIMM project to date were presented.
 
iSIMM looks beneath the Faroes basalt using low-frequency, long-offset seismic from Ocean Bottom Seismometers and Q-Marine streamers.
The iSIMM working group. Presented by Dr Roman Spitzer
Industry and university goals coincide in the integrated Seismic Imaging and Modelling of Margins (iSIMM) project whereby low frequency seismic energy, together with high-density, long-offset, single-sensor recordings, are used to penetrate volcanic overburdens and illuminate both the deep structure of magmatic margins and sub-basalt sediments in adjoining basins. continued ...
 
A Kinematic Fluid-flow Model of Sea-floor Spreading Initiation and Rifted Continental Margin Formation
N.J. Kusznir & the iSIMM Team
The observations of depth dependent lithosphere stretching at rifted continental margins and the exhumation of continental lithosphere mantle at non-volcanic margins are not explained by depth-uniform lithosphere stretching. Depth dependent lithosphere stretching, in which stretching of the continental lower crust and lithospheric mantle greatly exceeds that of the upper crust or upper crustal extension is entirely absent, is observed at both volcanic and non-volcanic margins. continued ...

AGU annual meeting, San Francisco, 13-17th December 2004

Four abstracts covering basin-modelling aspects of the iSIMM project were submitted to this conference:
 
A Kinematic Fluid-flow Model of Continental Lithosphere Deformation Leading to Continental Lithosphere Breakup and Rifted Continental Margin Formation -
a poster by Kusznir & Karner
The observations of depth dependent lithosphere stretching at rifted continental margins and the exhumation of continental lithosphere mantle at non-volcanic margins are not explained by depth-uniform lithosphere stretching. Depth dependent lithosphere stretching, in which stretching of the continental lower crust and lithospheric mantle greatly exceeds that of the upper crust or upper crustal extension is entirely absent, is observed at both volcanic and non-volcanic margins. continued ...
 
Deformation Kinematics of Rifted Continental Margin Lithosphere From Measured Bathymetry, Gravity and Upper Crustal Extension Using a New Model of Sea Floor Spreading Initiation -
a poster by Healy & Kusznir
We apply inverse methods to a two-dimensional coupled fluid-flow thermal model of sea floor spreading initiation and rifted continental margin formation in order to determine the rifted margin lithosphere deformation history and structure. The model assumes that stretching of continental lithosphere leading to breakup and sea floor spreading initiation is generated by an upwelling divergent flow field within continental lithosphere and asthenosphere. continued ...
 
The effect of temperature dependent rheology on a kinematic model of continental breakup and rifted continental margin formation -
a poster by Tymms & Kusznir
The effect of temperature dependent rheology has been examined for a model of continental lithosphere thinning by an upwelling divergent flow field within continental lithosphere and asthenosphere leading to continental breakup and rifted continental margin formation. The model uses a coupled FE fluid flow and thermal solution and is kinematically driven using a half divergence rate Vx and upwelling velocity Vz. Viscosity structure is modified by the evolving temperature field of the model through the temperature dependent Newtonian rheology. continued ...
 
Late Palaeocene Mantle Plume Uplift On The Fugløy Ridge, NE Faroes -
a poster by Hurst, Kusznir & Roberts
We apply inverse methods to a two-dimensional coupled fluid-flow thermal model of sea floor spreading initiation and rifted continental margin formation in order to determine the rifted margin lithosphere deformation history and structure. The model assumes that stretching of continental lithosphere leading to breakup and sea floor spreading initiation is generated by an upwelling divergent flow field within continental lithosphere and asthenosphere. continued ...
 
Each of the abstracts is available below:

Petrotech 6th International Conference, New Delhi, Jan 2005.

iSIMM demonstrates the benefit of high-fidelity, low frequency acquisition in sub-basalt imaging
Christie et al
Industry and university goals coincide in the integrated Seismic Imaging and Modeling of Margins (iSIMM) project whereby low frequency seismic energy, together with high-density, long-offset, single-sensor recordings, are used to penetrate volcanic overburdens and illuminate both the deep structure of magmatic margins and sub-basalt sediments in adjoining basins. Intracratonic basin models can successfully predict heat-flow and subsidence, and hence broad-brush hydrocarbon maturation, from basin stretching. However, these models cannot easily be extended to magmatic margins due to melt underplating and extrusion (i.e. crustal non-conservation), and depth dependent stretching: continued ...

Return to Rifts Conference, Geological Society, London, 5th-7th April 2005

Formation of Rifted Continental Margin Successor Basins by Depth-uniform and Depth-dependent Lithosphere Thinning: Predicting Subsidence and Heat Flow History
Kusznir & iSIMM team
Many rifted continental margins show breakup lithosphere thinning superimposed on single or multiple episodes of earlier intra-continental lithosphere stretching. The complexity of lithosphere deformation processes responsible for the formation of rifted margin successor basins has only recently been recognized. The prediction of subsidence and top basement heat-flow for these basins forms a substantial challenge both scientifically and technically in frontier exploration areas. continued ...

The geological history of rifts and rifted margins, revealed by 3D-flexural backstripping
Roberts, Kusznir et al
The technique of 3D flexural-backstripping and reverse thermal-subsidence modelling has been used to investigate the stratigraphic, tectonic and thermal history of rift basins now preserved in a variety of tectonic settings. Presented here are examples from three case studies, described in a sequence of increasing geological/tectonic complexity. The geological setting is outlined for each case, together with the objectives and achievements of the backstripping studies. continued ...

SEG-AGU Joint Assambly, New Orleans, 23rd - 27th May 2005

The Ocean-Continent Transition at the North Atlantic Continental Margins
White & iSIMM team
The continental margins of the northern North Atlantic are the best studied volcanic margins in the world. There is a wealth of integrated wide-angle and deep seismic profiles across the continent-ocean transition and the adjacent oceanic and continental crust, several of which form conjugate margin studies. We show new results from the integrated Seismic Imaging and Modelling of Margins (iSIMM) profiles across the Faroes continental margin which image both the extruded volcanics which generate seaward dipping reflector sequences and the underlying lower-crustal intrusions from which the extruded basalts are fed: continued ...

Predicting Structure and Location of the Ocean-Continent Transition at Rifted Margins Using a New Model of Continental Breakup and Rifted Margin Formation
Kusznir & iSIMM team
The structure and width of the ocean-continent transition (OCT) at rifted continental margins shows great diversity for both non-volcanic and volcanic margins. Some non-volcanic margins show broad regions of exhumed mantle within the OCT while others show broad regions of very thin upper continental crust above mantle. While many volcanic margins show a sharper OCT, others show broad regions of continental crustal thinning. continued ...

Application of a new model of continental lithosphere breakup and sea-floor spreading initiation to the Woodlark Basin western Pacific
Karner & Kusznir
A new model of continental lithosphere thinning leading to continental breakup has been applied to the most recent segment of sea-floor spreading initiation in the Woodlark ocean basin in the western Pacific. Sea-floor spreading in the Woodlark ocean basin commenced approximately 8 Ma ago in the east and has propagated westwards with time reaching the Moresby sea-mount region at the present day. The most recent segment of westward sea-floor spreading propagation initiated at the beginning of the Brunhes epoch. continued ...

Crustal Thickness Mapping of the Rifted Margin Ocean-Continent Transition using Satellite Gravity Inversion Incorporating a Lithosphere Thermal Correction
Hurst & Kusznir
A new method of inverting satellite gravity at rifted continental margins to give crustal thickness, incorporating a lithosphere thermal correction, has been developed which does not use a priori information about the location of the ocean-continent transition (OCT) and provides an independent prediction of OCT location. Satellite derived gravity anomaly data (Sandwell and Smith 1997) and bathymetry data (Gebco 2003) are used to derive the mantle residual gravity anomaly which is inverted in 3D in the spectral domain to give Moho depth. continued ...

Modelling of continental lithosphere breakup and rifted margin formation in response to an upwelling divergent flow field incorporating a temperature dependent rheology
Tymms & Kusznir
We numerically model continental lithosphere deformation leading to breakup and sea floor spreading initiation in response to an imposed upwelling and divergent flow field applied to continental lithosphere and asthenosphere. The model is used to predict rifted continental margin lithosphere thinning and temperature structure. Model predictions are compared with observed rifted margin structure for four diverse case studies. continued ...

Crustal Structure in the Southern Rockall Trough from Satellite Gravity Data: Evidence for Sea-floor Spreading
Chapell & Kusznir
The southern Rockall Trough south of 57N has previously been interpreted as either an intra-continental rift floored with highly extended continental crust, or a failed oceanic rift formed by Cretaceous sea floor spreading. Satellite gravity, bathymetry data and seismic estimates of sediment thickness are used to derive crustal basement thickness for the southern Rockall Trough and adjacent regions using a gravity inversion method incorporating a correction for the large negative thermal gravity component present in oceanic and stretched continental lithosphere. continued ...

EAGE 67th Conference & Exhibition, Madrid, 13th - 16th June 2005

Detailed insights into intra- and sub-basalt structures of the Faroe-Shetland basin extended abstract
Spitzer & iSIMM team
New seismic reflection data have been used to image intra- and sub-basalt features beneath the Faroe-Shetland basin in the North Atlantic, where flood basalts and their complex internal structure hinder successful seismic imaging. We demonstrate that acquisition and processing of low-frequency, long-offset marine seismic streamer data and recordings from ocean-bottom seismometers have the potential to enhance imaging and interpretation of seismic reflections from within and beneath basalts: continued ...

EGU General Assembly, Vienna, Austria, 24th - 29th April 2005

Four abstracts covering basin-modelling aspects of the iSIMM project have been submitted to this conference, together with one abstract on the seismic theme.
 
Modelling continental lithosphere thinning leading to breakup and sea-floor spreading initiation: The role of upwelling divergent flow within continental lithosphere -
Kusznir & Karner
A new model of continental lithosphere thinning leading to continental breakup and sea-floor spreading initiation has been developed which assumes that lithosphere thinning occurs in response to an upwelling divergent flow field within continental lithosphere and asthenosphere. continued ...
 
Kinematics of lithosphere breakup deformation at the Goban Spur rifted continental margin -
a poster by Healy & Kusznir
Deformation at a rifted continental margin during breakup and sea-floor spreading initiation can be described as the consequence of an upwelling divergent flow field within continental lithosphere and asthenosphere. A new model of lithosphere thinning leading to continental breakup and rifted margin formation (SfMargin) resulting from an upwelling divergent flow field has been developed. continued ...
 
Tertiary development of the Faroes-Shetland Basin: Intracontinental rifting or failed continental breakup? -
a poster by Fletcher, Kusznir & Roberts
The Faroes-Shetland Basin, an apparent intracontinental rift basin located to the north of the UK, is co-axial with the Moere rifted margin (NE Atlantic) to the north-eastwhich formed by sea-floor spreading initiation on the Aegir ridge at ˜ 54 Ma. While the Faroes-Shetland Basin lithosphere experienced Late Jurassic and Early Cretaceous intracontinental rifting, the basin also exhibits anomalously high rates of Palaeocene to Recent subsidence. continued ...
 
Crustal thickness mapping using satellite gravity data: Implications for the formation of the southern Rockall Trough -
a poster by Chappell & Kusznir
Satellite gravity and bathymetry data has been used to derive an upper bound of crustal basement thickness for the Rockall Trough and adjacent regions using a gravity inversion methodology incorporating a correction for the large negative thermal gravity anomaly component present in oceanic and stretched continental lithosphere. continued ...
 
Crustal Structure From The Faroes Shelf To The Norwegian Basin
a poster by A.W.Roberts et al
We present results from a tomographic inversion of a 400 km long wide-angle seismic line with 90 ocean bottom seismometers (OBS) stretching across the continental margin from west of the Shetlands to north of the Faroes. Basalt of up to 5 km thickness extends from the oceanic end to the continental Faroes-Shetland Trough and a low-velocity zone (probably pre-basalt sediment) stretches beneath the basalt from the continental margin across the entire Faroes Shelf. continued ...
 
Each of the abstracts is available below:

Petroleum Geoscience Collaboration, Geological Society London, 30th Nov - 1st Dec 2005

The Ocean-Continent Transition at North Atlantic Continental Margins
White & Christie & iSIMM team
The continental margins of the northern North Atlantic are some of the best studied volcanic margins in the world. There is a wealth of integrated wide-angle and deep seismic profiles across the continent-ocean transition and the adjacent oceanic and continental crust, several of which form conjugate margin studies. We show results from the Faroes Large Aperture Research Experiment (FLARE) and from the integrated Seismic Imaging and Modelling of Margins (iSIMM) profiles across the Faroes continental shelf and margin which image both the extruded volcanics which generate seaward dipping reflector sequences and the underlying lower-crustal intrusions from which the extruded basalts are fed.
continued ...

Integrating academic and industry techniques for looking beneath basalt
Christie, Lunnon, White, Spitzer & iSIMM Team
Scattering loss impacts seismic propagation through stacked basalt flows characterised by high impedance contrasts and/or rough interfaces. Such losses, together with related challenges from strong multiples and geometrical spreading, have hindered progress in imaging geology beneath magmatic overburdens. Building upon experience from previous seismic surveys in volcanic areas, and borehole observations of basalt characteristics which impact wave propagation, the integrated Seismic Imaging and Modelling of Margins (iSIMM) project has combined academic and industrial seismic techniques for looking beneath basalt.
continued ...

Crustal Structure of the Faroes North Atlantic Margin
Roberts AW & iSIMM team
We present results from a tomographic inversion of a 400 km long wide-angle seismic line with 90 ocean bottom seismometers (OBS) stretching across the continental margin from west of the Shetlands to north of the Faroes. The OBS profiles were acquired using a large airgun source comprising 14 guns with a total volume of 6,360 cu. in. towed at 20 m depth. The resulting output was dominated by low frequencies (peak at 9 Hz), which allowed imaging through the basalts and down to the upper mantle with strong arrivals recorded to c. 140 km range.
continued ...

Converted shear wave analysis from OBS deployed across the Faroes volcanic continental margin
a poster by Eccles, White, Christie & iSIMM team
A high quality combined reflection and wide angle seismic profile was acquired across the north-west European continental margin, in the vicinity of the Faroes Islands, as part of the Integrated Seismic Imaging and Modelling of Margins (iSIMM) project. Extensive flood basalt volcanism, associated with the Tertiary North Atlantic Igneous Province, provides a challenge to deep crustal imaging in the region because the cyclic, high impedance basalt flows are opaque to conventional seismic reflection techniques.
continued ...

Satellite gravity inversion for Moho depth incorporating a lithosphere thermal gravity anomaly correction: applications in frontier exploration at rifted margins
a poster by Chappell & Kusznir
Satellite gravity and bathymetry data can be used to derive an upper bound of crustal basement thickness at rifted continental margins in regions with no borehole or seismic data using a new method which incorporates a correction for the large negative thermal gravity component present in oceanic and stretched continental lithosphere (Kusznir et al 2004). The marine Bouguer anomaly derived from satellite free air gravity (Sandwell & Smith 1997) and GEBCO 2003 bathymetry data are inverted using the method of Oldenburg (1974), incorporating an iteratively applied lithosphere thermal anomaly correction, to give Moho depth.
continued ...

AGU annual meeting, San Francisco, 5-9th December 2005

Modes of Continental Lithosphere Deformation and Thinning Leading to Continental Breakup and Sea-floor Spreading Initiation
Kusznir & Healy
Continental breakup and sea-floor spreading initiation requires the thinning and rupture of continental lithosphere. For intra-continental lithosphere extension and rift basin formation, depth-uniform lithosphere stretching describes the main lithosphere responses of crustal thinning and geotherm perturbation and appears to be the dominant mode of lithosphere deformation; upper crustal fault extension balances the amount of lithosphere extension deduced from post-breakup thermal subsidence. In contrast both non-volcanic and volcanic rifted continental margins, including conjugate margin pairs, show depth-dependent lithosphere stretching in which stretching of the lower continental crust and lithosphere greatly exceeds that of the upper crust.
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Mapping the Ocean-Continent Transition at Rifted Margins using Satellite Gravity Inversion Incorporating a Lithosphere Thermal Correction
Hurst & Kusznir
Satellite gravity data and digital bathymetry provide powerful data sets for investigating the transition from continental to oceanic crust at rifted continental margins. The inversion of satellite gravity data at rifted continental margins to map crustal thickness variation and predict the location of the ocean-continent transition (OCT) requires the incorporation of a lithosphere thermal gravity anomaly correction for both oceanic and continental lithosphere.
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Investigating the Asymmetry of North Atlantic Volcanic Margins
a poster by Smith, White, & iSIMM Team
The Hatton Bank continental margin is a typical example of the volcanic margins present in the northern North Atlantic where voluminous magmatism occurred at the time of continental break-up. The upper crust exhibits characteristically large volumes of extruded lava imaged as seaward-dipping reflectors, which have in the past proved problematic for seismic imaging of the deeper crustal structure. The integrated Seismic Imaging and Modelling of Margins (iSIMM) project recorded profiles in 2002 designed to map specifically the poorly constrained lower crustal structure in this region.
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Evidence for a Slow Spreading Ocean Ridge in the Southern Rockall Trough From Satellite Gravity Inversion and Seismic Data
a poster by Chappell & Kusznir
The southern Rockall Trough, located to the west of Ireland and the UK in the NE Atlantic, has been interpreted as both a Mesozoic intra-continental rift basin (O’Reilly 1995) and a mid Cretaceous ocean basin (e.g. Roberts et al. 1980). We use satellite gravity inversion to map Moho depth and crustal thickness (Chappell & Kusznir 2005) for the Rockall Trough area.
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Tertiary formation of the Faroes-Shetland Basin, NE Atlantic rifted margin, by failed continental breakup
a poster by Fletcher, Kusznir, Roberts & Hunsdale
The Faroes-Shetland Basin, an apparent intracontinental rift basin located to the north of the UK, is co-axial with the Moere rifted margin to the north-east which formed by sea-floor spreading initiation on the Aegir ridge at ~ 54 Ma. Although the Faroes-Shetland Basin experienced Late Jurassic and Early Cretaceous rifting and subsequent thermal relaxation, well logging and paleoenvironment mapping indicates that the basin became emergent in the Late Paleocene, before experiencing anomalously high rates of subsidence in the early Eocene.
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