Sebastien Gac

• Corseri, Romain; Gac, Sebastien; Faleide, Jan Inge & Planke, Sverre (2020). The tectonized central peak of the Mjølnir Impact Crater, Barents Sea. Journal of Structural Geology.  ISSN 0191-8141.  131 . doi: 10.1016/j.jsg.2019.103953 Fulltekst i vitenarkiv. Vis sammendrag

  The Mjølnir structure, SW Barents Sea, is one of the best-preserved marine impact craters on Earth. After impact on the paleo-seafloor about 142 Ma ago, this crater experienced an atypical deformation of its central peak, which is now elevated ~435 m above the crater rims. Here, we investigate the effect of far-field tectonic stresses on the central peak uplift based on interpretation of new high-resolution P-Cable and conventional seismic reflection data. Nearby wells provided stratigraphic control on the interpreted horizons. The reconstruction of the crater sedimentary infill supports a subdued original central peak relief with a 5 km-wide, gentle mound ~15 m below the rim. Our interpretation shows that subvertical, outward-dipping, impact-induced faults were reactivated by uplifted segments of the central peak up to 500 m above the platform level during one or several contractional episodes. We postulate that post-Albian tectonic compressional events triggered the structural uplift of the Mjølnir central peak. Differential compaction, previously seen as the main deformation process, may have increased the original central peak height by only ~10 m. The mobilization of impact-shattered rocks by tectonic compression provides a new and robust explanation for the structural rise of Mjølnir's central peak.

• Gac, Sebastien; Minakov, Alexander; Shephard, Grace; Faleide, Jan Inge & Planke, Sverre (2020). Deformation analysis in the Barents Sea in relation to paleogene transpression along the Greenland-Eurasia plate boundary. Tectonics.  ISSN 0278-7407.  39(10) . doi: 10.1029/2020TC006172 Fulltekst i vitenarkiv. Vis sammendrag

  Late Cretaceous‐Cenozoic contractional structures are widespread in the Barents Sea. While the exact dating of the deformation is unclear, it can only be inferred that the contraction is younger than the early Cretaceous. One likely contractional mechanism is related to Greenland Plate kinematics at Paleogene times. We use a thin sheet finite element modeling approach to compute deformation within the Barents Sea in response to the Greenland‐Eurasia relative motions during the Paleogene. The analytical solution for the 3‐D folding of sediments above basement faults is used to assess possibilities for folding. Two existing Greenland Plate kinematic models, differing slightly in the timing, magnitude, and direction of motion, are tested. Results show that the Greenland Plate's general northward motion promotes growing anticlines in the entire Barents Sea shelf. Our numerical models suggest that the fan‐shaped pattern of cylindrical anticlines in the Barents Sea can be associated with the Eurekan deformation concurrent to the initial rifting and early seafloor spreading in the northeast Atlantic. The main contraction phase in the SW Barents Sea coincides with the timing of continental breakup, whereas the peak of deformation predicted for the NW Barents Sea occurred at later times. Svalbard has experienced a prolonged period of compressional deformation. We conclude that Paleogene Greenland Plate kinematics are a likely candidate to explain contractional structures in the Barents Sea

• Gac, Sebastien; Hansford, Peter Anthony & Faleide, Jan Inge (2018). Basin modelling of the SW Barents Sea. Marine and Petroleum Geology.  ISSN 0264-8172.  95, s 167- 187 . doi: 10.1016/j.marpetgeo.2018.04.022 Fulltekst i vitenarkiv.
• Indrevær, Kjetil; Gac, Sebastien; Gabrielsen, Roy Helge & Faleide, Jan Inge (2018). Crustal-scale subsidence and uplift caused by metamorphic phase changes in the lower crust: A model for the evolution of the Loppa High area, SW Barents Sea from late Paleozoic to Present. Journal of the Geological Society.  ISSN 0016-7649.  175(3), s 497- 508 . doi: 10.1144/jgs2017-063 Fulltekst i vitenarkiv.
• Gac, Sebastien; Klitzke, Peter; Minakov, Alexander; Faleide, Jan Inge & Scheck-Wenderoth, Magdalena (2016). Lithospheric strength and elastic thickness of the Barents Sea and Kara Sea region. Tectonophysics.  ISSN 0040-1951.  691(Part A), s 120- 132 . doi: 10.1016/j.tecto.2016.04.028
• Gac, Sebastien; Huismans, Ritske; Simon, Nina Simone C; Faleide, Jan Inge & Podladchikov, Yuri Y. (2014). Effects of lithosphere buckling on subsidence and hydrocarbon maturation: A case-study from the ultra-deep East Barents Sea basin. Earth and Planetary Science Letters.  ISSN 0012-821X.  407, s 123- 133 . doi: 10.1016/j.epsl.2014.09.029
• Gac, Sebastien; Huismans, Ritske; Simon, Nina Simone C; Podladchikov, Yuri Y. & Faleide, Jan Inge (2013). Formation of intracratonic basins by lithospheric shortening and phase changes: a case study from the ultra-deep East Barents Sea basin. Terra Nova.  ISSN 0954-4879.  25(6), s 459- 464 . doi: 10.1111/ter.12057
• Gac, Sebastien; Huismans, Ritske; Podladchikov, Yuri P. & Faleide, Jan Inge (2012). On the origin of the ultradeep East Barents Sea basin. Journal of Geophysical Research (JGR): Solid Earth.  ISSN 2169-9313.  117 . doi: 10.1029/2011JB008533
• Steer, Philippe; Huismans, Ritske; Valla, Pierre G.; Gac, Sebastien & Herman, Frédéric (2012). Bimodal Plio-Quaternary glacial erosion of fjords and low-relief surfaces in Scandinavia. Nature Geoscience.  ISSN 1752-0894.  5(9), s 635- 639 . doi: 10.1038/NGEO1549
• Gac, Sebastien & Geoffroy, L (2009). 3D Thermomechanical modelling of a stretched continental lithosphere containing localized low-viscosity anomalies (the soft-point theory of plate break-up). Tectonophysics.  ISSN 0040-1951.  468(1-4), s 158- 168 . doi: 10.1016/j.tecto.2008.05.011
• Gac, Sebastien; Tisseau, Chantal; Dyment, Jérôme & Goslin, Jean (2006). Modelling the thermal evolution of slow-spreading ridge segments and their off-axis geophysical signature. Geophysical Journal International.  ISSN 0956-540X.  164(2), s 341- 358 . doi: 10.1111/j.1365-246X.2005.02844
• Gargani, J; Geoffroy, L; Gac, Sebastien & Cravoisier-Auge, S (2006). Fault slip and Coulomb stress variations around a pressured magma reservoir: consequences on seismicity and magma intrusion. Terra Nova.  ISSN 0954-4879.  18(6), s 403- 411

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• Gabrielsen, Roy Helge; Faleide, Jan Inge; Wong, P.W; Gac, Sebastien; Indrevær, Kjetil; Faisal Miraj, M.; Dinkgreve, Patricia; Sokoutis, Dimitrios & Pascal, Christophe (2017). Palaeogene North Atlantic opening along the Barents Sea margin and its adjacent deformation.
• Gac, Sebastien; Indrevær, Kjetil; Gabrielsen, Roy Helge & Faleide, Jan Inge (2017). A model of the tectonic evolution of the Loppa High from Late Paleozoic to present-day.
• Indrevær, Kjetil; Gabrielsen, Roy Helge; Gac, Sebastien & Faleide, Jan Inge (2017). Is there a tectonic signal in the development of the late Palaeozoic bioherms on the Loppa High?.
• Indrevær, Kjetil; Gac, Sebastien; Gabrielsen, Roy Helge & Faleide, Jan Inge (2017). Can metamorphic phase changes in the lower crust help explain the repeated uplift and subsidence of the Loppa High area through time?.
• Gac, Sebastien & Faleide, Jan Inge (2016). Contractional structures in the Barents Sea: Insights from numerical modeling.
• Klitzke, Peter; Scheck-Wenderoth, Magdalena; Gac, Sebastien; Faleide, Jan Inge; Minakov, Alexander & Sippel, Judith (2016). Structure and Temperature Configuration of the Barents Sea and Kara Sea region and implications for its lithospheric strength.
• Faleide, Jan Inge; Gabrielsen, Roy Helge; Indrevær, Kjetil; Gac, Sebastien; Minakov, Aleksander; Miraj, M.F. & Pascal, Christophe (2015). Contractional events in the Barents Sea basin evolution - timing, causes and implications.
• Gac, Sebastien; Clark, Stephen A; Minakov, Alexander & Faleide, Jan Inge (2015). On the relevance of basin formation mechanisms on the maturation of source rocks: A case study from the East Barents Sea basin.
• Klitzke, Peter; Gac, Sebastien; Faleide, Jan Inge & Scheck-Wenderoth, Magdalena (2015). Lithospheric Strength and elastic thickness of the Barents Sea and Kara Sea region.
• Gac, Sebastien; Clark, A; Minakov, Alexander & Faleide, Jan Inge (2014). On the relevance of basin formation mechanisms on the maturation of source rocks: A case study from the East Barents Sea basin.
• Gac, Sebastien & Faleide, Jan Inge (2014). A tectonic model for the Central and East Barents Sea from Early Palaeozoic to Early Jurassic.
• Gac, Sebastien & Faleide, Jan Inge (2014). Control of lithosphere structure on surface deformation in the Central Barents Sea: insights from dynamical modeling.
• Gac, Sebastien; Huismans, Ritske; podladckikov, Yuri & Simon, Nina (2009). Can phase changes be at the origin of the large subsidence of Barents Sea basins? Insights from density modelling.
• Gac, Sebastien; Huismans, N.S; Simon, J.S. & Podladchikov, Y.Y. (2008). Are phase changes at the origin of the large subsidence of Barents Sea basins? Insights from dynamic numerical modelling.
• Gac, Sebastien; Austegard, Atle; Huismans, Ritske & Mjelde, Rolf (2007). Influence of lower crustal flow on the post-rift subsidence of a basin.
• Gac, Sebastien; Geoffroy, L & Callot, J.P. (2007). Analogue and numerical modeling of the soft point hypothesis.
• Gac, Sebastien; Huismans, Ritske & Austegard, Atle (2007). Role of lower crustal flow during post-rift sedimentary basin evolution.
• Geoffroy, L; Leroy, M.; Gac, Sebastien & Callot, J.P. (2007). Magmatism and extensión at LIP-related volcanic rifts and volcanic margins.
• Gac, Sebastien; Austegard, Atle & Huismans, Ritske (2006). Differences between kinematic and dynamic models of extensional lithosphere.
• Gac, Sebastien; Austegard, Atle & Huismans, Ritske (2006). Dynamic modeling of crustal extension.
• Gac, Sebastien & Geoffroy, L (2006). 3D thermo-mechanical modeling of a stretched continental lithosphere containing "soft points".
• Gac, Sebastien; Huismans, Ritske & Austegard, Atle (2006). Dynamic models of lithosphere extension using extension.

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