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Expedition 302 summary

Record type: Conference or Workshop Item (Paper)

The first scientific drilling expedition to the central Arctic Ocean was completed in September 2004. Integrated Ocean Drilling Program Expedition 302, Arctic Coring Expedition (ACEX), recovered sediment cores to 428 meters below seafloor (mbsf) in water depths of ~1300 m, 250 km from the North Pole.
Expedition 302's destination was the Lomonosov Ridge, hypothesized to be a sliver of continental crust that broke away from the Eurasian plate at ~56 Ma. As the ridge moved northward and subsided, marine sedimentation occurred and continues to the present, resulting in what was anticipated from seismic data to be a continuous paleoceanographic record. The elevation of the ridge above the surrounding abyssal plains (~3 km) ensured that sediments atop the ridge were free of turbidites. The primary scientific objective of Expedition 302 was to continuously recover this sediment record and to sample the underlying sedimentary bedrock by drilling and coring from a stationary drillship.
The biggest challenge during Expedition 302 was maintaining the drillship's location while drilling and coring in 2–4 m thick sea ice that moved at speeds approaching 0.5 kt. Sea-ice cover over the Lomonosov Ridge moves with one of the two major Arctic sea-ice circulation systems, the Transpolar Drift, and responds locally to wind, tides, and currents. Until now, the high Arctic Ocean Basin, known as "mare incognitum" within the scientific community, had never before been deeply cored because of these challenging sea-ice conditions.
Initial results reveal that biogenic carbonate is present only in the Holocene–Pleistocene interval. The upper 198 mbsf represents a relatively high sedimentation rate record of the past 18 m.y. and is composed of sediment with ice-rafted debris and dropstones, suggesting that ice-covered conditions extended at least this far back in time. Details of the ice type (e.g., iceberg versus sea ice), timing, and characteristics (e.g., perennial versus seasonal) await further study. A hiatus occurs at 193.13 mbsf, spanning a 25 m.y. interval from the early Miocene to the middle Eocene between ~18 Ma and 43 Ma. The sediment record during the middle Eocene is of dark, organic-rich biosiliceous composition. Isolated pebbles, interpreted as ice-rafted dropstones, are present down to 239 mbsf, well into this middle Eocene interval. Around the lower/middle Eocene boundary an abundance of Azolla spp. occurs, suggesting that a fresh and/or low-salinity surface water setting dominated the region during this time period. Although predrilling predictions based on geophysical data had placed the base of the sediment column at 50 Ma, drilling revealed that the uppermost Paleocene to lowermost Eocene boundary interval, well known as the Paleocene/Eocene Thermal Maximum (PETM), was recovered. During the PETM, the temperature of the Arctic Ocean surface waters exceeded 20°C.
Drilling during Expedition 302 also penetrated into the underlying sedimentary bedrock, revealing a shallow-water depositional environment of Late Cretaceous age.

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Citation

Backman, J., Moran, K., McInroy, D., Brinkhuis, H.K., Clemens, S., Cronin, T., Dickens, G.R., Eynaud, F., Gattacceca, J., Jakobsson, M., Jordan, R.W., Kaminski, M., King, J., Koç, N., Martinez, N.C., Matthiessen, J., Moore, T.C., Onodera, J., O'Regan, M., Pälike, H., Rea, B.R., Rio, D., Sakamoto, T., Smith, D.C., Stein, R., St. John, K.E.K., Suto, I., Suzuki, N., Takahashi, K., Watanabe, M. and Yamamoto, M., (2006) Expedition 302 summary Backman, J., Moran, K., McInroy, D.B. and Mayer, L.A. (eds.) In Proceedings of the Integrated Ocean Drilling Program, Vol. 302. Integrated Ocean Drilling Program Management International, Inc., 22pp. (doi:10.2204/iodp.proc.302.101.2006).

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Published date: 7 March 2006

Identifiers

Local EPrints ID: 41914
URI: http://eprints.soton.ac.uk/id/eprint/41914
PURE UUID: f4421701-adae-4d07-ae9c-f65b23c6c93e

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Date deposited: 16 Oct 2006
Last modified: 17 Jul 2017 15:25

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Contributors

Author: J. Backman
Author: K. Moran
Author: D. McInroy
Author: H.K. Brinkhuis
Author: S. Clemens
Author: T. Cronin
Author: G.R. Dickens
Author: F. Eynaud
Author: J. Gattacceca
Author: M. Jakobsson
Author: R.W. Jordan
Author: M. Kaminski
Author: J. King
Author: N. Koç
Author: N.C. Martinez
Author: J. Matthiessen
Author: T.C. Moore
Author: J. Onodera
Author: M. O'Regan
Author: H. Pälike
Author: B.R. Rea
Author: D. Rio
Author: T. Sakamoto
Author: D.C. Smith
Author: R. Stein
Author: K.E.K. St. John
Author: I. Suto
Author: N. Suzuki
Author: K. Takahashi
Author: M. Watanabe
Author: M. Yamamoto
Editor: J. Backman
Editor: K. Moran
Editor: D.B. McInroy
Editor: L.A. Mayer

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