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1. Site U1554

   Parnell-Turner, RE; Briais, A; LeVay, LJ; Cui, Y; Di_Chiara, A; Dodd, JP; Dunkley_Jones, T; Dwyer, D; Eason, DE; Friedman, SA; et al (January 2025, Proceedings of the International Ocean Discovery Program Expedition reports)

   Site U1554 is located on Björn drift, on the eastern flank of the Reykjanes Ridge in the North Atlantic Ocean. The Reykjanes Ridge flanks host a series of crustal V-shaped ridges (VSRs) and V-shaped troughs (VSTs) (Figure F1), whose origins and relation with Iceland mantle plume temperature variations are debated. Site U1554 is located on VST 2b, identifiable in the free-air gravity anomaly map and the reflection seismic profile (Figure F2). It sits on ocean crust with an age of 12.7 Ma estimated from magnetic anomalies and plate reconstruction models. The Reykjanes Ridge flanks are also the site of major drift deposits: Björn and Gardar drifts on the eastern flank of the ridge and Eirik drift on the eastern flank of the Greenland margin. These rapidly accumulated contourite drift sediments have the potential to record variations in past climate and ocean circulation on millennial timescales. The sedimentation rate of the drifts can serve as a proxy for deep water current strength, providing information on oceanic gateways to the Norwegian Sea and their potential ties to Iceland mantle plume behavior. 

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2. Expedition 395 Scientific Prospectus Addendum: Reykjanes Mantle Convection and Climate

   https://doi.org/10.14379/iodp.sp.395add.2023  

   Parnell-Turner, R.; Briais, A.; LeVay, L. (April 2023, Scientific prospectus)

   The intersection between the Mid-Atlantic Ridge and Iceland hotspot provides a natural laboratory where the composition and dynamics of Earth’s upper mantle can be observed. Plume-ridge interaction drives variations in the melting regime, which result in a range of crustal types, including a series of V-shaped ridges and V-shaped troughs south of Iceland. Expedition 395 has three objectives: (1) to test contrasting hypotheses for the formation of V-shaped ridges, (2) to understand temporal changes in ocean circulation and explore connections with plume activity, and (3) to reconstruct the evolving chemistry of hydrothermal fluids with increasing crustal age and varying sediment thickness and crustal architecture. After being postponed from summer 2020 due to the COVID-19 pandemic, the drilling objectives of Expedition 395 were partially completed without a science party on board during Expedition 395C in summer 2021, when basalt cores were collected at four sites (U1554, U1555, U1562, and U1563). Sediment cores were collected from these sites, as well as from Site U1564, and casing was installed to 602 meters below seafloor at Site U1554. Expedition 395 is scheduled with sufficient time to complete the planned operations remaining at Sites U1564 and U1554, leaving approximately 22 operating days available for other sites, including a new proposed site, REYK-14B, which is located west of Reykjanes Ridge on the Eirik drift. This addendum provides the operations plan for rescheduled Expedition 395, including details of the additional site. 

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3. Expedition 395 Preliminary Report: Reykjanes Mantle Convection and Climate: Mantle Dynamics, Paleoceanography and Climate Evolution in the North Atlantic Ocean

   Parnell-Turner, R; Briais, A; LeVay, L (May 2024, Preliminary report)

   The intersection between the Mid-Atlantic Ridge and Iceland hotspot provides a natural laboratory where the composition and dynamics of Earth's upper mantle can be observed. Plume-ridge interaction drives variations in the melting regime, which result in a range of crustal types, including a series of V-shaped ridges (VSRs) and V-shaped troughs (VSTs) located south of Iceland. Mantle upwelling beneath Iceland dynamically supports regional bathymetry and may lead to changes in the height of oceanic gateways, which in turn control the flow of deep water on geologic timescales. This expedition recovered basaltic samples from crust that is blanketed by thick sediments, that also contain climatic and oceanic records from modern to earliest Oligcene/late Eocene times. Major, trace, and isotope geochemistry of basalts from this expedition provide insight into spatial and temporal variations in mantle melting processes. These samples will enable testing of the hypothesis that the Iceland plume thermally pulses on two timescales (5–10 and ~30 Ma), leading to fundamental changes in crustal architecture. This idea will be tested against alternative hypotheses involving propagating rifts and buoyant mantle upwelling. Millennial-scale paleoclimate records are contained in the rapidly accumulated sediments of contourite drifts cored during Expedition 395. The accumulation rate of these sediments is a proxy for current strength, which is moderated by dynamic support of oceanic gateways such as the Greenland-Scotland Ridge. These sediments also provide constraints for climatic events including Miocene and Pliocene warmth, the intensification of Northern Hemisphere glaciation, and abrupt Late Pleistocene climate change. The integrated approach of Expedition 395 allows the relationships between deep Earth processes, ocean circulation, and climate to be explored. These objectives were addressed by recovering sediment and basement cores from four sites, plus an additional two sites which were completed during Expeditions 384 and 395C (U1555 and U1563). Two sites (U1554 and U1562) are located in Björn drift above a VSR/VST pair, and another site targeted the Holocene–Eocene sequence of sediments at Eirik drift, located on the eastern Greenland margin (U1602). The fourth site of Expedition 395 (U1564) is located on 32.4 My-old oceanic crust that is devoid of V-shaped features, and was chosen because it intersects the Holocene to Oligo–Miocene sedimentary sequence of Gardar drift. Considered together, the sediments, basalts and vast array of measurements collected during Expedition 395 will provide a major advance in our understanding of mantle dynamics and the linked nature of Earth's interior, oceans, and climate. 

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4. Expedition 395 summary

   Parnell-Turner, RE; Briais, A; LeVay, LJ; Cui, Y; Di_Chiara, A; Dodd, JP; Dunkley_Jones, T; Dwyer, D; Eason, DE; Friedman, SA; et al (January 2025, Proceedings of the International Ocean Discovery Program Expedition reports)

   The intersection between the Mid-Atlantic Ridge and Iceland hotspot provides a natural laboratory where the composition and dynamics of Earth's upper mantle can be observed. Plume-ridge interaction drives variations in the melting regime, which result in a range of crustal types, including a series of V-shaped ridges (VSRs) and V-shaped troughs (VSTs) located south of Iceland. Mantle upwelling beneath Iceland dynamically supports regional bathymetry, and its variations may lead to changes in the height of oceanic gateways, which in turn control the flow of deep water on geologic timescales. Expeditions 384, 395C, and 395 recovered extensive successions of basaltic crust and thick (up to 1.3 km) overlying sediment cover, including successions through a number of contourite drifts of regional significance. Major, trace, and isotope geochemistry of basalts recovered during these expeditions will provide insight into spatial and temporal variations in mantle melting processes. Such analyses will provide data for testing the hypothesis that the Iceland plume thermally pulses on two timescales (5–10 and ~30 Ma), leading to fundamental changes in crustal architecture. This idea will be tested against alternative hypotheses involving propagating rifts and buoyant mantle upwelling. The rapidly accumulated sediments of contourite drifts have the potential to yield exceptional millennial-scale paleoceanographic records, including proxies for current strength, which is thought to be modulated by the dynamic support of the Greenland-Scotland Ridge, an oceanic gateway of global import. The recovered sediments also provide a record of subarctic climate change stretching back to the latest Eocene, including the long-term evolution of the Greenland ice sheet, critical intervals of Miocene and Pliocene warmth, the intensification of Northern Hemisphere glaciation, and Pleistocene millennial-scale variability. The objectives of Expeditions 395, 395C, and 384 are to explore the relationships between deep Earth processes, ocean circulation, and climate. These objectives were addressed by recovering sediment and basement cores from six sites, completed across three expeditions. Sites U1555 and U1563 are located at a VST/VSR pair nearest to the Reykjanes Ridge, on ~2.8 and 5.2 My old crust, respectively. Sites U1554 and U1562 are located in Björn drift above a VST/VSR pair, on ~12.4 and 14.2 My old crust, respectively. Site U1564 is located in Gardar drift above 32.4 My old oceanic crust that is devoid of V-shaped features. Finally, Site U1602 is located on the eastern Greenland margin above crust that is estimated to be Eocene in age and thus formed during the initial separation of Greenland from Scandinavia. Considered together, the sediments, basalts, and vast array of measurements collected during Expeditions 395, 395C, and 384 will provide a major advance in our understanding of mantle dynamics and the linked nature of Earth's interior, oceans, and climate. 

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5. Reykjanes Mantle Convection and Climate

   https://doi.org/10.14379/iodp.proc.395.2025  

   Parnell-Turner, RE; Briais, A; LeVay, LJ (January 2025, Proceedings of the International Ocean Discovery Program Expedition reports)

   The intersection between the Mid-Atlantic Ridge and Iceland hotspot provides a natural laboratory where the composition and dynamics of Earth's upper mantle can be observed. Plume-ridge interaction drives variations in the melting regime, which result in a range of crustal types, including a series of V-shaped ridges (VSRs) and V-shaped troughs (VSTs) located south of Iceland. Mantle upwelling beneath Iceland dynamically supports regional bathymetry, and its variations may lead to changes in the height of oceanic gateways, which in turn control the flow of deep water on geologic timescales. Expeditions 384, 395C, and 395 recovered extensive successions of basaltic crust and thick (up to 1.3 km) overlying sediment cover, including successions through a number of contourite drifts of regional significance. Major, trace, and isotope geochemistry of basalts recovered during these expeditions will provide insight into spatial and temporal variations in mantle melting processes. Such analyses will provide data for testing the hypothesis that the Iceland plume thermally pulses on two timescales (5–10 and ~30 Ma), leading to fundamental changes in crustal architecture. This idea will be tested against alternative hypotheses involving propagating rifts and buoyant mantle upwelling. The rapidly accumulated sediments of contourite drifts have the potential to yield exceptional millennial-scale paleoceanographic records, including proxies for current strength, which is thought to be modulated by the dynamic support of the Greenland-Scotland Ridge, an oceanic gateway of global import. The recovered sediments also provide a record of subarctic climate change stretching back to the latest Eocene, including the long-term evolution of the Greenland ice sheet, critical intervals of Miocene and Pliocene warmth, the intensification of Northern Hemisphere glaciation, and Pleistocene millennial-scale variability. The objectives of Expeditions 395, 395C, and 384 are to explore the relationships between deep Earth processes, ocean circulation, and climate. These objectives were addressed by recovering sediment and basement cores from six sites, completed across three expeditions. Sites U1555 and U1563 are located at a VST/VSR pair nearest to the Reykjanes Ridge, on ~2.8 and 5.2 My old crust, respectively. Sites U1554 and U1562 are located in Björn drift above a VST/VSR pair, on ~12.4 and 14.2 My old crust, respectively. Site U1564 is located in Gardar drift above 32.4 My old oceanic crust that is devoid of V-shaped features. Finally, Site U1602 is located on the eastern Greenland margin above crust that is estimated to be Eocene in age and thus formed during the initial separation of Greenland from Scandinavia. Considered together, the sediments, basalts, and vast array of measurements collected during Expeditions 395, 395C, and 384 will provide a major advance in our understanding of mantle dynamics and the linked nature of Earth's interior, oceans, and climate. 

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