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Your search keyword '"Minshull, Tim A."' showing total 48 results
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48 results on '"Minshull, Tim A."'

8. Comparison of two- and three-dimensional full waveform inversion imaging using wide-angle seismic data from the Deep Galicia Margin

Author

Boddupalli, Bhargav, Minshull, Tim A., Morgan, Joanna, Bayrakci, Gaye, and Klaeschen, Dirk

Abstract

Full waveform inversion (FWI) is a data-fitting technique capable of generating high-resolution velocity models with a resolution down to half the seismic wavelength. FWI is applied typically to densely sampled seismic data. In this study, we applied FWI to 3D wide-angle seismic data acquired using sparsely spaced ocean bottom seismometers (OBSs) from the Deep Galicia Margin west of Iberia. Our dataset samples the S-reflector, a low-angle detachment present in this area. Here we highlight differences between 2D, 2.5D and 3D-FWI performances using a real sparsely spaced dataset. We performed 3D FWI in the time domain and compared the results with 2D and 2.5D FWI results from a profile through the 3D model. When overlaid on multichannel seismic images, the 3D FWI results constrain better the complex faulting within the pre- and syn-rift sediments and crystalline crust compared to the 2D result. Furthermore, we estimate variable serpentinisation of the upper mantle below the S-reflector along the profile using 3D FWI, reaching a maximum of 45 per cent. Differences in the data residuals of the 2D, 2.5D and 3D inversions suggest that 2D inversion can be prone to overfitting when using a sparse dataset. To validate our results, we performed tests to recover the anomalies introduced by the inversions in the final models using synthetic datasets. Based on our comparison of the velocity models, we conclude that the use of 3D data can partially mitigate the problem of receiver sparsity in FWI.

Published
2021

10. The importance of rift history for volcanic margin formation

Author

Armitage, John J., Collier, Jenny S., and Minshull, Tim A.

Subjects
Faults (Geology) -- Research, Continental margins -- Research, Magmatism -- Research, Environmental issues, Science and technology, Zoology and wildlife conservation
Abstract

Rifting and magmatism are fundamental geological processes that shape the surface of our planet. A relationship between the two is widely acknowledged but its precise nature has eluded geoscientists and remained controversial. Largely on the basis of detailed observations from the North Atlantic Ocean, mantle temperature was identified as the primary factor controlling magmatic production (1), with most authors seeking to explain observed variations in volcanic activity at rifted margins in terms of the mantle temperature at the time of break-up (2,3). However, as more detailed observations have been made at other rifted margins worldwide, the validity of this interpretation and the importance of other factors in controlling break-up style have been much debated (4-7). One such observation is from the northwest Indian Ocean, where, despite an unequivocal link between an onshore flood basalt province, continental break-up and a hot-spot track leading to an active ocean island volcano, the associated continental margins show little magmatism (5,8). Here we reconcile these observations by applying a numerical model that accounts explicitly for the effects of earlier episodes of extension. Our approach allows us to directly compare break-up magmatism generated at different locations and so isolate the key controlling factors. We show that the volume of rift-related magmatism generated, both in the northwest Indian Ocean and at the better-known North Atlantic margins, depends not only on the mantle temperature but, to a similar degree, on the rift history. The inherited extensional history can either suppress or enhance melt generation, which can explain previously enigmatic observations., Extensive surveys in the North Atlantic have shown that the breakup of Europe from North America was characterized by massive episodes of igneous activity. Such large magmatic events are potentially [...]

Published
2010
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11. Tectonosedimentary evolution of the deep Iberia-Newfoundland margins: evidence for a complex breakup history

Author

Peron-Pinvidic, Gwenn, Manatschal, Gianreto, Minshull, Tim A., and Sawyer, Dale S.

Subjects
Newfoundland (Island) -- Natural history, Iberian Peninsula -- Natural history, Morphotectonics -- Research, Earth sciences
Abstract

[1] Most of the conceptual ideas concerning sedimentary architecture and tectonic evolution of deep tiffed margins are based on either intracontinental rift basins or proximal margins, both of which underwent only small amounts of crustal thinning. In this paper, we investigate the tectonosedimentary and morphotectonic evolution related to continental breakup of the highly extended, deep Iberia-Newfoundland margins. Our results show that continental breakup is a complex process distributed in time and space. On the basis of mapping of dated seismic units and borehole data we are able to identify two major phases of extension. During a first phase, dated as Tithonian to Barremian (145-128 Ma), deformation is related to exhumation of mantle rocks; basins become younger oceanward, and fault geometry changes from upward to downward concave resulting in complex sedimentary structures and basin geometries. A second phase, dated as latest Aptian (112 Ma), overprints previously exhumed mantle and accreted juvenile oceanic crust over more than 200 km leading to the formation of basement highs. The observed complex breakup history challenges classical concepts of rifting and leads to new interpretations for the tectonosedimentary evolution of deep rifted margins.

Published
2007

19. 3D development of detachment faulting during continental breakup

Author

Lymer, Gaël, primary, Cresswell, Derren J.F., additional, Reston, Tim J., additional, Bull, Jonathan M., additional, Sawyer, Dale S., additional, Morgan, Julia K., additional, Stevenson, Carl, additional, Causer, Annabel, additional, Minshull, Tim A., additional, and Shillington, Donna J., additional

Published
2019
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20. Elastic and electrical properties and permeability of serpentinites from Atlantis Massif, Mid-Atlantic Ridge

Author

Falcon-Suarez, Ismael, Bayrakci, Gaye, Minshull, Tim A., North, Laurence J., Best, Angus I., Rouméjon, Stéphane, IODP Expedition 357 Science Party, National Oceanography Centre [Southampton] (NOC), University of Southampton, Institut de Physique du Globe de Paris (IPGP), Institut national des sciences de l'Univers (INSU - CNRS)-IPG PARIS-Université Paris Diderot - Paris 7 (UPD7)-Université de La Réunion (UR)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université de La Réunion (UR)-Université Paris Diderot - Paris 7 (UPD7)-IPG PARIS-Institut national des sciences de l'Univers (INSU - CNRS)

Subjects
Electrical properties, Permeability and porosity, Acoustic properties, Mid-ocean ridge processes, 010504 meteorology & atmospheric sciences, Mineralogy, Mid-Atlantic Ridge, 010502 geochemistry & geophysics, 01 natural sciences, Petrography, Geochemistry and Petrology, Oceanic crust, Ultramafic rock, 14. Life underwater, Petrology, ComputingMilieux_MISCELLANEOUS, 0105 earth and related environmental sciences, Peridotite, geography, geography.geographical_feature_category, Massif, Seafloor spreading, Tectonics, Geophysics, 13. Climate action, [SDU]Sciences of the Universe [physics], Geology
Abstract

Geophysical Journal International, 211 (2), ISSN:0956-540X, ISSN:1365-246X

Published
2017

22. Resistivity image beneath an area of active methane seeps in the west Svalbard continental slope

Author

Goswami, Bedanta K., Weitemeyer, Karen, Minshull, Tim, Sinha, Martin, Westbrook, Graham, and Marin Moreno, Hector

Abstract

The Arctic continental margin contains large amounts of methane in the form of methane hydrates. The west Svalbard continental slope is one area where active methane seeps have been reported near the landward limit of the hydrate stability zone. The presence of bottom simulating reflectors (BSR) on seismic reflection data in water depths greater than 600 m provides evidence for the presence of hydrate. Resistivity obtained from marine controlled source electromagnetic (CSEM) data provides a useful complement to seismic methods for detecting shallow hydrate and gas. We therefore acquired two CSEM lines in the west Svalbard continental slope, extending from the edge of the continental shelf to water depths of around 800~m. High resistivities (5-12 Ohm-m) observed above the BSR support the presence of gas hydrate in water depths greater than 600 m. High resistivities (3-4 Ohm-m) at 390-600~m water depth also suggest possible hydrate occurrence within the gas hydrate stability zone (GHSZ) of the continental slope. In addition, high resistivities (4-8 Ohm-m) landward of the GHSZ are coincident with high-amplitude reflectors and low velocities reported in seismic data that indicate the likely presence of free gas. Saturation estimates using a connectivity equation suggest 20-50% hydrate within the lower slope sediments and around 6% within the upper slope sediments. A free gas zone beneath the GHSZ (10-20% gas saturation) is connected to the high free gas saturated (10-45%) area at the edge of the continental shelf, where most of the seeps are observed. This evidence supports the presence of lateral free gas migration beneath the GHSZ towards the continental shelf.

Published
2016

25. Deep structure of the Porcupine Basin from wide-angle seismic data

Author

Watremez, Louise, primary, Prada, Manel, additional, Minshull, Tim, additional, O'Reilly, Brian, additional, Chen, Chen, additional, Reston, Tim, additional, Shannon, Pat, additional, Wagner, Gerlind, additional, Gaw, Viola, additional, Klaeschen, Dirk, additional, Edwards, Rose, additional, and Lebedev, Sergei, additional

Published
2016
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33. Escape of methane gas from the seabed along the West Spitsbergen continental margin

Author

Westbrook, Graham, Thatcher, Kate E., Rohling, Eelco J., Piotrowski, Alexander M., Pälike, Heiko, Osborne, Anne, Nisbet, Euan G., Minshull, Tim A., Lanoisellé, Mathias, James, Rachael H., Hühnerbach, Veit, Green, Darryl, Fisher, Rebecca E., Crocker, Anya J., Chabert, Anne, Bolton, Clara, Beszczynska-Möller, Alfred, Berndt, Christian, Aquilina, Alfred, Clemens, Steven, Kuhnt, Wolfgang, National Oceanography Centre [Southampton] ( NOC ), University of Southampton [Southampton], Department of Earth Sciences, University of Cambridge, National Oceanography Centre, Southampton, School of Ocean and Earth Science, Department of Earth Sciences [Egham], Royal Holloway [University of London] ( RHUL ), National Environment Research Council, Department of Basic Medical Sciences, University of Arizona, Géoazur ( GEOAZUR ), Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Université Nice Sophia Antipolis ( UNS ), Université Côte d'Azur ( UCA ) -Université Côte d'Azur ( UCA ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de la Côte d'Azur, Université Côte d'Azur ( UCA ) -Centre National de la Recherche Scientifique ( CNRS ), GEOMAR - Helmholtz Centre for Ocean Research [Kiel] ( GEOMAR ), Department of Earth, Environmental and Planetary Sciences [Providence], Brown University, Institute of Geosciences, Christian-Albrechts-Universität zu Kiel ( CAU ), National Oceanography Centre [Southampton] (NOC), University of Southampton, Department of Earth Sciences [Cambridge, UK], University of Cambridge [UK] (CAM), Ocean and Earth Science [Southampton], University of Southampton-National Oceanography Centre (NOC), Royal Holloway [University of London] (RHUL), Helmholtz Centre for Ocean Research [Kiel] (GEOMAR), Institute of Geosciences [Kiel], Christian-Albrechts-Universität zu Kiel (CAU), Géoazur (GEOAZUR 6526), Observatoire de la Côte d'Azur, Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Côte d'Azur (UCA)-COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Nice Sophia Antipolis (... - 2019) (UNS), and COMUE Université Côte d'Azur (2015 - 2019) (COMUE UCA)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Recherche pour le Développement (IRD)-Centre National de la Recherche Scientifique (CNRS)

Subjects
[ SDE.MCG ] Environmental Sciences/Global Changes, [SDU]Sciences of the Universe [physics], [SDE.MCG]Environmental Sciences/Global Changes, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2009

34. Escape of methane gas from the seabed along the West Spitsbergen continental margin

Author

Westbrook, Graham K., Thatcher, Kate E., Rohling, Eelco J., Piotrowski, Alexander M., Pälike, Heiko, Osborne, Anne H., Nisbet, Euan G., Minshull, Tim A., Lanoisellé, Mathias, James, Rachael H., Huhnerbach, Veit, Green, Darryl, Fisher, Rebecca E., Crocker, Anya J., Chabert, Anne, Bolton, Clara, Beszczynska-Möller, Agnieszka, Berndt, Christian, and Aquilina, Alfred

Abstract

More than 250 plumes of gas bubbles have been discovered emanating from the seabed of the West Spitsbergen continental margin, in a depth range of 150– 400 m, at and above the present upper limit of the gas hydrate stability zone (GHSZ). Some of the plumes extend upward to within 50 m of the sea surface. The gas is predominantly methane. Warming of the northward-flowing West Spitsbergen current by 1° C over the last thirty years is likely to have increased the release of methane from the seabed by reducing the extent of the GHSZ, causing the liberation of methane from decomposing hydrate. If this process becomes widespread along Arctic contine ntal margins, tens of Teragrams of methane per year could be released into the ocean.

Published
2009

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