North Atlantic marine sediments

North Atlantic marine sediments
Name	North Atlantic marine sediments
Region	North Atlantic Ocean
Type	Marine sediment
Primary lithology	Pelagic clay; calcareous ooze; siliceous ooze; terrigenous mud
Namedfor	North Atlantic Ocean

North Atlantic marine sediments are the depositional materials accumulating on the seafloor of the North Atlantic Ocean basin, recording interactions among Plate tectonics, Pleistocene, Holocene, and anthropogenic influences. These sediments archive signals from ice sheets (for example, the Laurentide Ice Sheet and Greenland Ice Sheet), the Gulf Stream, the North Atlantic Drift, and major climatic events such as the Younger Dryas and the Younger Dryas stadial. Studies integrate work by institutions like the Woods Hole Oceanographic Institution, the National Oceanic and Atmospheric Administration, and the International Ocean Discovery Program to reconstruct past environments and predict future changes.

Geology and Sedimentology

The seafloor of the North Atlantic Ocean includes geomorphic provinces such as the Mid-Atlantic Ridge, continental margins of Iceland, Greenland, Iberia, and the Grand Banks of Newfoundland, and bathymetric features like the Rockall Trough, the Porcupine Abyssal Plain, and the Azores Plateau. Tectonic processes driven by the North American Plate and the Eurasian Plate control subsidence, creating accommodation for sediment accumulation studied via cores recovered by expeditions of the Deep Sea Drilling Project and the Ocean Drilling Program. Stratigraphic frameworks reference boundaries from the Pleistocene epoch, tephra from Eyjafjallajökull and Laki eruptions, and mass-transport deposits linked to the Storegga Slide and the Fogo Seamounts.

Sediment Composition and Sources

Sediment types derive from contributions of biogenic components like foraminifera (e.g., genera such as Neogloboquadrina and Globigerina), coccolithophores (e.g., Emiliania huxleyi), radiolarians, and diatoms, producing calcareous ooze and siliceous ooze that mix with terrigenous inputs from the Amazon River (via long transport), the Mississippi River (indirect via circulation), and European rivers such as the Seine and Loire River. Glacially derived tills, ice-rafted debris (IRD) from the Laurentide Ice Sheet and Scandinavian Ice Sheet, and volcanic ash layers (tephra) from the Iceland plume also contribute distinct mineralogies (e.g., clay minerals like illite and smectite, and heavy minerals including zircon and magnetite). Authigenic minerals such as authigenic carbonates and manganese nodules form under redox gradients influenced by bottom-water ventilation from the North Atlantic Current.

Depositional Environments and Processes

Depositional settings include inner shelf depositional systems offshore Norway, slope fans such as those off Newfoundland, abyssal plains like the Hatton-Rockall Basin, and contourite deposits formed by persistent currents including the Labrador Current and the Gulf Stream. Processes include turbidity currents generated on the continental slope leading to turbidites, contour current reworking forming drifts adjacent to the Rockall Bank, and pelagic settling of biogenic particles producing laminated oozes in areas of low bottom agitation (for example, the Porcupine Abyssal Plain time-series site). Mass-wasting events tied to sea-level change and seismicity, such as slide complexes along the Shetland platform, redistribute sediments and produce stratigraphic discontinuities used to correlate records across cores.

Paleoceanographic and Climate Records

Sediments preserve proxies—stable isotopes (δ18O, δ13C) from benthic and planktonic foraminifera, alkenone unsaturation indices (UK'37) from Emiliania huxleyi, and biomarkers like TEX86—used to reconstruct sea-surface temperature, salinity, and ventilation related to episodes documented by the Younger Dryas, the Last Glacial Maximum, and Dansgaard–Oeschger events. Ice-rafted debris layers mark Heinrich events (e.g., Heinrich event 1), while laminated sapropels and intervals of reduced carbonate preservation indicate shifts in carbonate compensation depth influenced by changes in the Atlantic Meridional Overturning Circulation and freshwater pulses from meltwater routing via the St. Lawrence River or the Mackenzie River. Correlation with ice-core records from Greenland (for instance, NGRIP) and marine terraces provides chronological control using radiocarbon dating and tephrochronology tied to Eldgjá and other eruptions.

Biogeochemical Cycling and Carbon Sequestration

Organic carbon burial in continental shelves and deeper basins modulates atmospheric CO2 on glacial–interglacial timescales, with processes mediated by primary productivity (linked to upwelling zones near Iceland and nutrient inputs), remineralization, and oxygen exposure on the shelf. Redox-sensitive trace metals (e.g., molybdenum, uranium) and nitrogen isotopes in sediments record past bottom-water oxygenation tied to changes in the North Atlantic Current and the Atlantic Multidecadal Oscillation. Methane seeps associated with gas hydrate stability on the continental margin, and authigenic carbonate pavements, indicate episodes of methane release that interact with global carbon budgets and are studied for their role in abrupt climate perturbations similar to events inferred from the Paleocene–Eocene Thermal Maximum.

Human Impacts and Anthropogenic Signals

Anthropogenic signatures include radionuclide fallout (e.g., from Chernobyl disaster and nuclear weapons testing), increased microplastic concentrations, heavy metal enrichment from industrial centers such as Liverpool and Rotterdam, and eutrophication signals traced to agricultural runoff from rivers including the Seine and Rhine River. Shipping and deep-sea mining proposals near the Azores and the Mid-Atlantic Ridge raise concerns about disturbance to sedimentary carbon sinks and benthic habitats studied by organizations like the International Seabed Authority and research programs managed by the European Marine Board.

Category:Marine geology Category:North Atlantic Ocean Category:Paleoceanography