ODP Site 980

ODP Site 980
Name	Site 980
Expedition	Ocean Drilling Program Leg 162
Location	Rockall Plateau, North Atlantic
Water depth	~2270 m
Drilled	1996
Coordinate	~57°N, 21°W

ODP Site 980

Site 980 was drilled on the Rockall Plateau during Ocean Drilling Program Leg 162 to investigate Neogene to Quaternary sedimentation, paleocirculation, and climate change. The site provided continuous cores that documented shifts in Atlantic circulation, ice sheet dynamics, and biotic turnovers across the Pliocene–Pleistocene transition. Work at the site integrated stratigraphy, foraminiferal biostratigraphy, isotope geochemistry, and paleoceanographic proxy development used widely by researchers studying North Atlantic Ocean and high-latitude climate evolution.

Location and Geological Setting

Site 980 lies on the Rockall Plateau southwest of Iceland and northwest of Ireland on the northeastern margin of the Atlantic Ocean basin. The Rockall Plateau is bounded by the Eurasian Plate and influenced by the Mid-Atlantic Ridge system and adjacent basins such as the Porcupine Seabight and the Sleipner Ridge region. Tectonically, the area records Mesozoic rifting and Cenozoic subsidence associated with the opening of the North Atlantic and plate reorganizations tied to the Iceland plume. Oceanographic setting is controlled by the interaction between the North Atlantic Current, the Labrador Sea outflow, and subpolar gyre dynamics modulated by glacial–interglacial cycles recorded in the surrounding continental margins like the Rockall Trough.

Drilling and Core Recovery

Leg 162 operations deployed the drillship JOIDES Resolution under the management of the Ocean Drilling Program in 1996, with drilling supervised by a joint team including scientists from institutions such as the British Geological Survey, Scripps Institution of Oceanography, Lamont–Doherty Earth Observatory, and the University of Cambridge. Rotary coring and advanced piston corer tools recovered continuous sediment sections including hemipelagic muds, contourites, and glacigenic deposits. Core recovery rates were enhanced by stratigraphic correlation with nearby sites like those on the Rockall Bank and by use of downhole logging tools developed by the International Continental Scientific Drilling Program affiliates and engineering teams from Schlumberger partners.

Lithology and Stratigraphy

Cores from Site 980 record a succession of Pliocene to Quaternary lithologies including calcareous muds, silty clays, and diamictic layers attributed to iceberg rafting and contour current reworking. Stratigraphic architecture shows repeated alternations of carbonate-rich intervals and carbonate-poor glacimarine units comparable to sections from the Norwegian Sea margin and Iceland Plateau. Key horizons correlate to regional marker events such as the Mid-Pleistocene Transition and the onset of Northern Hemisphere glaciation documented at archives like the Greenland Ice Sheet cores and North Atlantic Deep Water records.

Paleoclimatic and Paleoceanographic Findings

Interpretations from Site 980 emphasize changes in surface productivity, stratification, and deep-water formation linked to shifts in the North Atlantic Current and episodes of iceberg discharge contemporaneous with events like the Marine Isotope Stage 100 through Marine Isotope Stage 2. Evidence supports phasing between North Atlantic sea-surface temperature variability and continental records from sites such as Loch Lomond and the Bering Strait gateway influences. Comparisons with paleoclimate reconstructions from the European Project for Ice Coring in Antarctica and the North Greenland Ice Core Project have been used to refine leads and lags between high-latitude cryosphere changes and Atlantic overturning.

Biostratigraphy and Age Control

Biostratigraphic control at Site 980 relied on planktonic foraminifera zonations, calcareous nannofossil events, and datums tied to the Geologic Time Scale calibrations used by the International Commission on Stratigraphy. Taxa such as Globigerina bulloides, Neogloboquadrina pachyderma, and nannofossils like Emiliania huxleyi and Coccolithus pelagicus provided primary markers, supplemented by paleomagnetic stratigraphy tied to Brunhes–Matuyama and other chrons recognized in records from the Mid-Atlantic Ridge sites. Radiometric tie points from intercalated ash layers correlated with eruption histories of volcanic centers including Iceland and the Hebridean Igneous Province aided age assignments.

Geochemical and Isotopic Analyses

Geochemical analyses at Site 980 encompassed stable isotopes (δ18O, δ13C) from benthic and planktonic foraminifera, trace-metal proxies such as Mg/Ca and Ba/Ca, and bulk sediment elemental ratios measured with instruments used at facilities like Woods Hole Oceanographic Institution and Max Planck Institute for Chemistry. Results document variations in deep-water temperature, carbonate compensation depth shifts, and nutrient upwelling linked to changes observed in North Atlantic Deep Water production. Organic geochemistry including alkenone Uk'37 paleothermometry and biomarker fluxes tied to productivity were cross-validated with records from the Sargasso Sea and Irminger Sea.

Scientific Impact and Subsequent Research

Data from Site 980 contributed to paradigms about Neogene–Quaternary climate evolution, influencing syntheses by research groups at the National Oceanography Centre, Brown University, and the Alfred Wegener Institute. The site provided calibration points for coupled climate models developed at institutions such as Princeton University and MIT and informed paleoceanographic compilations in meta-analyses published by teams at CNRS and GEOMAR. Subsequent coring initiatives, including those under the International Ocean Discovery Program, have revisited the Rockall Plateau citing Site 980 as a benchmark for sedimentological, isotopic, and paleoceanographic comparisons across the North Atlantic basin.

Category:Ocean Drilling Program sites