This dataset was produced during the Eurofleets + PORO-CLIM cruise. Project PORO-CLIM was conceived to study interplay between the first-order geological processes of continental rifting and break-up, Large Igneous Province emplacement, and global climate change, and to provide ship-based training for a cohort of international students. Cruise CE21008, the PORO-CLIM data acquisition cruise, carried out a marine geophysical survey of the POrcupine and ROckall continental passive margins, to investigate the cause of the Paleocene/Eocene Thermal Maximum, a natural CLIMate change event that is the closest deep-time analogue of anthropogenic environmental change (though the modern change is happening much faster). Project PORO-CLIM also includes a three-year post-cruise data work-up phase. The €1.2M project is funded by the EU Horizon 2020 EuroFleets+ programme, the PIPCO-RSG industrial consortium and the Irish Marine Research Programme. OBJECTIVES OF CRUISE CE21008 1. A controlled-source deep seismic imaging programme using 27 Ocean Bottom Seismometers (OBSs) and a 1 km multi-channel seismic streamer of the following targets: (a) Rockall Plateau passive margin and Erriador Ridge. (b) Porcupine Seabight, Porcupine passive margin abyssal plain and the East Thulean Rise. 2. Provide multi-disciplinary training early career researcher (masters and PhD level) in techniques of controlled source seismology (OBS and MCS), physical oceanography and marine mammal observing, and in research areas of mantle processes, tectonic processes, sedimentary processes and physical oceanographic processes. 3. Carry out an outreach programme, led by the early career researcher team, that communicates scientific and technical aspects of the work to an audience from primary school children to adults. SUMMARY CRUISE NARRATIVE Despite the Covid pandemic, the cruise went ahead with a science party of 13, including about half the planned compliment of early career researchers. The cruise began after a 14-day pre-cruise lock-down period, followed by Covid-safe travel to the vessel. We lost 1.5 days at the start owing to equipment shipping delays. At sea we had 4.5 days of full weather downtime, and had to alter our work programme on a further 4.5 days, mostly to avoid bad weather, and the rest (1 day) because of OBS equipment failure. Nevertheless, we ended by acquiring the 1st and 3rd on our priority list of deep seismic profiles. We made 47 ocean bottom seismometers (OBS) deployments, acquired 800 km of seismic reflection data and coincident magnetometer data, and deployed 66 expendable bathythermograph (XBT) probes. The data are of good quality and can address all the scientific aims. The outreach objective was particularly successful, and generated over 100,000 audience engagements across Europe and beyond. LONG-TERM OBJECTIVES OF PORO-CLIM The following objectives will be addressed based directly on the dataset acquired on cruise CE21008 over the next three years. 1. Obtain continuous mantle temperature history from Late Cretaceous (Santonian) to Eocene. 2. Test models for initiation of the North Atlantic Igneous Province (NAIP). 3. Test whether the NAIP alone drove the Paleocene/Eocene Thermal Maximum (PETM) global warming event. 4. Explain the temporal transition from magma-poor to magma-rich passive margins in the North Atlantic. Successful hypotheses tests would confirm the dominant role of mantle temperature in controlling passive margin structure [24]. 5. Image continental rifting modes within Porcupine Basin. 6. Determine how the palaeogeography and sediment supply systems of Porcupine and Rockall Basins evolved through Cretaceous-Eocene. 7. Infer Cretaceous-Cenozoic deep-water palaeoceanographic evolution from the seismic architecture of contourite sediment drifts. Submitted underway data to EMODnet Data Ingestion: AIS, EUcaws, fluorometer, Gill wind direction, SBE21 thermosalinograph. The €1.2M project is funded by the EU Horizon 2020 EuroFleets+ programme, the PIPCORSG industrial consortium and the Irish Marine Research Programme .

This dataset was produced during the Eurofleets + PORO-CLIM cruise. Project PORO-CLIM was conceived to study interplay between the first-order geological processes of continental rifting and break-up, Large Igneous Province emplacement, and global climate change, and to provide ship-based training for a cohort of international students. Cruise CE21008, the PORO-CLIM data acquisition cruise, carried out a marine geophysical survey of the POrcupine and ROckall continental passive margins, to investigate the cause of the Paleocene/Eocene Thermal Maximum, a natural CLIMate change event that is the closest deep-time analogue of anthropogenic environmental change (though the modern change is happening much faster). Project PORO-CLIM also includes a three year post-cruise data work-up phase. 65 expendable bathytherograph (XBT) probes (T-5, T-11) were deployed to constrain the seismic velocity in the water layer. Sound speed was calculated assuming a constant salinity of 34.9 psu. The €1.2M project is funded by the EU Horizon 2020 EuroFleets+ programme, the PIPCORSG industrial consortium and the Irish Marine Research Programme.