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Highlights • Determination of the tectonomagmatic evolution of the NW Atlantic • Mapping of the breakup-related magmatism using the vocanostratigraphy concept • Mapping of the magnetic and gravimetric crustal domain patterns and their boundaries using integrated SGM method • Analyses of seabed and onshore samples and field analogues work • New plate tectonic reconstruction for the NW Atlantic Abstract Passive margins are the locus of tectonic and magmatic processes leading to the formation of highly variable along-strike and conjugate margins structures. Using extensive new seismic, gravity, and magnetic datasets, complemented by seabed samples and field work, we investigate the tectonomagmatic evolution of the northwest (NW) Atlantic where breakup-related igneous rocks were emplaced during several Paleogene events associated with lithospheric stretching, continental breakup, and the formation of new oceanic basins. Interpretational methods include integrated seismic-gravity-magnetic (SGM) interpretation and seismic volcanostratigraphy. In addition, seabed and field samples were collected and analyzed to constrain the basin stratigraphy, hydrocarbon potential, and the geochronology and geochemistry of the volcanic sequences. Offshore, 2D seismic data reveal several Seaward Dipping Reflector (SDR) wedges and escarpments in the Labrador Sea, Davis Strait, and Baffin Bay. Onshore, eastward prograding foreset-bedded hyaloclastite delta deposits and overlying horizontal lava successions outcrop on Nuussuaq. These hyaloclastites and lava successions are world class analogues to the Lava Delta and Landward Flows volcanic seismic facies units identified offshore. Our mapping results document an aerial extent of the Paleogene breakup-related volcanics of 0.3 × 106 km2, with an estimated volume of 0.5–0.6 × 106 km3. Basalt samples recovered by dredging the Upernavik Escarpment have late Paleocene to/early Eocene ages, whereas the sedimentary samples provide an excellent seism

Injection of CO2 in subsurface reservoirs may cause overburden deformation and CO2 leakage. The aim of this study is to apply technologies for detection and monitoring of CO2 leakage and deformation above the injection reservoirs. The examples of this study include data from the Vestnesa Ridge natural seep site, the Snøhvit gas field and CO2 storage site region, and the Gemini North gas reservoir. Reprocessing of existing 3D high-resolution seismic data allows resolving features with a vertical and lateral resolution down to c. 1 m and c. 5 m respectively. The current acquisition systems could be modified to image structures down to one meter in both the vertical and horizontal directions. We suggest a monitoring workflow that includes baseline and time-lapse acquisition of high-resolution 3D seismic data, integrated with geochemical, geophysical, and geotechnical seabed core and water-column measurements. The outcome of such a workflow can deliver reliable quantitative property volumes of the subsurface and will be able to image meter-sized anomalies of fluid leakage and deformation in the overburden.

Age determinations were conducted on detrital zircon grains from two stratigraphic levels in the Postmasburg Group, Transvaal Supergroup - the top of the Makganyene Formation and the base of the Hotazel Formation - to constrain the age of the group and for comparison with purported correlatives in the Segwagwa Group of the Kanye basin and Pretoria Group of the Transvaal basin. Detrital zircon grains are interpreted as being derived mainly from the underlying Ghaap Group and its basement of Ventersdorp Supergroup and Kraaipan granite/greenstone rocks, indicating a proximal source to the east and north on the Vryburg arch. The maximum age of the Postmasburg Group was constrained by the youngest detrital-zircon age to 2436. ±. 7. Ma and the broad age range of the group, as a consequence, to somewhere between 2.43 and 2.38. Ga. Comparison with various stratigraphic units in the Kanye and Transvaal basins indicated close similarities in zircon populations with the Duitschland Formation in the Transvaal basin. The Pretoria and Segwagwa Groups contain younger zircon populations at 2350-2320 and 2240-2200. Ma that are related to syn-depositional volcanic activity and are not present in the Postmasburg Group samples, indicating the younger age of these groups. Based on compatibility of zircon populations, new stratigraphic correlations between the upper groups of the Transvaal Supergroup in the Griqualand West, Kanye and Transvaal basins are proposed. These include the probable restriction of the lower Timeball Hill - Hekpoort portion of the Pretoria Group to the Transvaal basin. An older age for the Postmasburg Group - ≈2.4. Ga as opposed to the generally accepted 2.22. Ga - will affect various models proposed for the evolution of the Earth's atmosphere/hydrosphere that have been based on studies of rocks of the group, supporting an older ≈2.4. Ga age for global oxidation transformations.