Find out about the scientific programme of the MSM119 cruise (provided by MARUM).

The research cruise MSM119 focused on the systematic investigations of sedimentary ponds and crustal ridges on the eastern flank of the southernmost tip of the Reykjanes Ridge (57.50° - 57.65° N, 32.85°-32.15° W). A total of 14 gravity cores were successfully collected along a transect from very young crust (approximately 0.1 Ma near the ridge axis) to crustal ages of up to ~3 Ma, and in a sedimentary pond, referred to as “Squid Pond” (previously identified during cruise M183) further away from the ridge axis, underlain by crust of ~4 Ma.

The Reykjanes ridge, characterized by a full spreading rate of approximately 20 mm/yr, offers a unique opportunity to explore the connections between glacial-interglacial cycles and magmatic processes beneath slow-spreading ridges. Central questions are whether magmatic activity at such ridges reflects temporal variations corresponding to glacial cycles, and how these connections differ from those observed at intermediate- to fast-spreading ridges. Addressing these questions integrates sediment-hosted glass geochemistry, hydrothermal activity, and crustal thickness assessments, etc. Distinctive features of the Reykjanes ridge, such as its V-shaped ridges potentially linked to the southward propagation of the Iceland hotspot, provide further scope for exploration under the T-SECTOR initiative. Key questions include the influence of the Iceland plume on sediment-hosted glass geochemistry and the extent of such an impact, if there are any glass shards from Iceland eruptions and the possibility of tracing temporal changes in volcanic activity on Iceland over extended timescales (up to ~1 Ma) and correlating them with glacial-interglacial cycles? By studying the sediment samples and the available seismic data from this cruise, these questions can be explored.

The study primarily focuses on cores with crustal age younger than 1.5 Ma, owing to the actual recovery length and high sedimentation rates. Initial analyses of major and trace elements in two cores (~0.3 Ma and ~0.5 Ma) reveal compositional fluctuations (e.g., ~10% variation in K₂O) with sediment depth, which may reflect sea-level-driven changes in magma production. XRF data and imaging scans also indicate possible temporal variations in hydrothermal activity. Preliminary age models, based on benthic δ¹⁸O and radiocarbon (¹⁴C) dating, suggest that these two cores may have covered the Last Glacial Maximum to the last interglacial period. Parasound and seismic data also help reveal the bathymetry changes and the sediment thickness, underscoring a high and variable sedimentation rate in this study area An intriguing discovery is the compositional similarity of many sediment-hosted glass fragments to Iceland volcanic basalts and rhyolites. Isotopic and volatile content analyses are underway to pinpoint their volcanic origins. When combined with precise age models, these findings may illuminate long-term variations of specific Iceland volcanoes and the influence of glacial-interglacial cycles on Iceland volcanic system. This ongoing study on samples from cruise MSM119 is expected to yield comprehensive insights into the connections between sea-level changes and magmatic processes along the Reykjanes Ridge. Final results and conclusions are anticipated in the coming years, contributing valuable knowledge to the broader T-SECTOR framework.

Daily log of the cruise with photos of life onboard and the scientific work carried out.