ODP Hole 980

ODP Hole 980
Name	Hole 980
Expedition	Ocean Drilling Program Leg 162
Location	North Atlantic Ocean, Madeira Abyssal Plain
Latitude	33°N (approx.)
Longitude	24°W (approx.)
Water depth	~4,500 m
Drilled depth	~300 mbsf
Primary objectives	Paleoclimatology, Pleistocene stratigraphy, turbidite analysis
Operator	Ocean Drilling Program

ODP Hole 980 is a borehole drilled during the Ocean Drilling Program focused on deep-sea sedimentary records within the North Atlantic. The hole recovered a high-resolution Pleistocene to Neogene sequence used to study Milankovitch cycles, Pleistocene glaciations, and North Atlantic circulation tied to the Atlantic Meridional Overturning Circulation. Results from the site have informed work on teleconnections connecting the North Atlantic Oscillation, Younger Dryas, and Mediterranean outflow dynamics.

Background and Location

Hole 980 lies on the Madeira Abyssal Plain near the flanks of the Mid-Atlantic Ridge and proximal to the Azores Triple Junction. The site was selected to capture distal turbidites and hemipelagic deposition influenced by sediment routing from the Iberian Peninsula, Madeira Islands, and the Tagus Abyssal Plain. Placement considered earlier cores from sites such as cores recovered by the Deep Sea Drilling Project and seismic profiles from the RRS Discovery and R/V Joides Resolution surveys. The geological setting connects to the bathymetric highs of the Cabo Verde Fracture Zone and sediment sources linked to the Gulf of Cádiz.

Drilling Expedition and Methods

Drilling at the hole was executed during a leg of the Ocean Drilling Program employing the drillship JOIDES Resolution and standard ODP rotary coring tools, including the advanced piston corer and extended core barrel systems. Logging included downhole measurements analogous to tools used on the D/V Glomar Challenger, such as gamma ray and resistivity sensors. Shipboard analyses combined smear-slide lithology with physical property measurements, following protocols developed during Leg 162 and integrated with post-cruise studies at laboratories affiliated with institutions like Woods Hole Oceanographic Institution, Scripps Institution of Oceanography, and the University of Cambridge.

Lithology and Stratigraphy

Recovered sequences comprise alternating hemipelagic marls, clay-rich muds, and interbedded turbiditic sand layers reflecting episodic gravity flows. Stratigraphic interpretation uses lithostratigraphic units correlated to seismic reflectors mapped earlier by teams from the National Oceanography Centre and seismic lines tied to the European Geophysical Society datasets. Key intervals show pronounced turbidite signatures comparable to deposits described off the Iberian Margin and correlate with layers studied in cores from the Lofoten Basin and Rockall Trough for planktonic foraminifer preservation.

Paleontology and Microfossils

Microfossil assemblages include planktonic foraminifera, calcareous nannofossils, and benthic foraminifera used to reconstruct surface and bottom-water conditions. Taxa observed mirror regional assemblages known from studies at Bermuda Rise, Cape Verde Rise, and Portugal Margin, with notable occurrences of Globigerina bulloides, Neogloboquadrina pachyderma, and species tied to the Eocene–Oligocene transition in comparative sequences. Ostracod and radiolarian fragments supplement biostratigraphic resolution, paralleling paleontological frameworks developed at the British Antarctic Survey and Lamont–Doherty Earth Observatory.

Geochronology and Age Constraints

Age models integrate oxygen isotope stratigraphy calibrated to the global benthic δ18O stack and magnetostratigraphic tie points correlated with geomagnetic polarity timescales from laboratories such as Paleomagnetics Research Group centers. Radiometric age control uses correlation with nearby sites dated by Argon–Argon dating and correlation to astronomical tuning of precession and obliquity cycles, leveraging methods advanced in studies led by researchers affiliated with ETH Zurich and University of Arizona. The core spans late Neogene through the Pleistocene, enabling identification of Marine Isotope Stages including intervals synchronous with the Last Glacial Maximum.

Paleoenvironmental Interpretations

Sedimentological and microfossil indicators point to variability in productivity, dust flux, and bottom-water oxygenation modulated by shifts in North Atlantic circulation and Mediterranean Outflow strength. High sand turbidites correlate with enhanced slope instability events contemporaneous with meltwater pulses identified in records from Greenland Ice Sheet Project cores and correlated to abrupt events like the Heinrich events. Stable isotope gradients imply changes in surface water temperature and salinity tied to Atlantic Multidecadal Oscillation-scale variability, while increased carbonate dissolution in some intervals reflects deep water acidity changes analogous to observations from Baffin Bay and Svalbard margin studies.

Scientific Significance and Subsequent Research

The hole contributed critical data for reconstructing North Atlantic overturning variability, sediment transport pathways from the Iberian margin, and the timing of Pleistocene climatic events. Findings have been cited in syntheses addressing teleconnections between North Atlantic climate and Mediterranean circulation, influencing models developed at National Center for Atmospheric Research, Max Planck Institute for Meteorology, and MPI for Marine Microbiology. Follow-up investigations have reanalyzed cores with high-resolution geochemical proxies at facilities including GEOMAR, IFREMER, and the University of Bergen, and integrated Hole 980 data into basin-scale compilations led by the International Ocean Discovery Program and paleoceanographic research networks.

Category:Ocean Drilling Program boreholes