TY - JOUR

T1 - Hemipelagic deposits on the Mendeleev and northwestern Alpha submarine Ridges in the Arctic Ocean

T2 - Acoustic stratigraphy, depositional environment and an inter-ridge correlation calibrated by the ACEX results

AU - Bruvoll, Vibeke

AU - Kristoffersen, Yngve

AU - Coakley, Bernard J.

AU - Hopper, John R.

N1 - Funding Information: Acknowledgement We thank captain D. Oliver and the crew of the USCG icebreaker Healy. Healy cruise 0503 by NSF award # 0449898 to Geophysical Institute, University of Alaska, Fairbanks, and # 0447440 to Texas A&M University, College Station, Texas. MCS acquisition and Norwegian participation in Healy cruise 0503 was funded by the Norwegian Petroleum Directorate. We are grateful to the Healy (2005) Seismic Team (Paul Henkart, Scripps Institution of Oceanography, USA; Tore Arthun, Hans Berge and Erik Grindvoll, University of Bergen, Norway; Hedda Breien, University of Oslo, Norway; Dayton Dove, University of Alaska, Fairbanks, USA; Nina Ivanova, University of Uppsala, Sweden; Fredrik Ludvigsen, Thor Heyerdahl High School, Larvik, Norway; and Karina Monsen, Alta High School, Alta Norway) for their effort and companionship during the cruise. We also thank two anonymous reviewers for their efforts and constructive comments.

PY - 2010/9

Y1 - 2010/9

N2 - The first high resolution multichannel seismic data from the Mendeleev and Alpha Ridges in the Arctic Ocean have been used to investigate the depositional history, and compare acoustic stratigraphies of the three main sub-marine ridges (Mendeleev, Alpha and Lomonosov) in the polar ocean. Acoustic basement on the Mendeleev Ridge is covered by a ~0.6-0.8 s thick sediment drape over highs and up to 1.8 s within grabens. A pronounced angular discordance at 0.18-0.23 s below the seafloor along the middle to upper slopes divides the succession into an upper, undisturbed, uniformly thick, hemipelagic drape (Unit M1) and a partially truncated lower unit (Unit M2) characterized by strong reflection bands. Unit M2 is thicker in intra-ridge grabens and includes three sub-units with abundant debris flows in the uppermost subunit (M2a). The discordance between Units M1 and M2 most likely relates to instability along the middle to upper slopes and mass wasting, triggered by tectonic activity. The scars were further smoothed by bottom current erosion. We observe comparable acoustic stratigraphy and discordant relationships on the investigated northwestern part of Alpha Ridge. Similarly, on the central Lomonosov Ridge, Paleocene and younger sediments sampled by scientific drilling include an uppermost ~0.2 s thick drape overlying, highly reflective deposits with an angular unconformity confined to the upper slope on both sides of the ridge. Sediment instability on the three main ridges was most likely generated by a brief phase of tectonic activity (~14.5-22 Ma), coinciding with enhanced bottom circulation. These events are coeval with the initial opening of the Fram Strait. The age of the oldest sediments above acoustic basement on the Mendeleev- and west-central Alpha Ridges is estimated to be 70-75 Ma.

AB - The first high resolution multichannel seismic data from the Mendeleev and Alpha Ridges in the Arctic Ocean have been used to investigate the depositional history, and compare acoustic stratigraphies of the three main sub-marine ridges (Mendeleev, Alpha and Lomonosov) in the polar ocean. Acoustic basement on the Mendeleev Ridge is covered by a ~0.6-0.8 s thick sediment drape over highs and up to 1.8 s within grabens. A pronounced angular discordance at 0.18-0.23 s below the seafloor along the middle to upper slopes divides the succession into an upper, undisturbed, uniformly thick, hemipelagic drape (Unit M1) and a partially truncated lower unit (Unit M2) characterized by strong reflection bands. Unit M2 is thicker in intra-ridge grabens and includes three sub-units with abundant debris flows in the uppermost subunit (M2a). The discordance between Units M1 and M2 most likely relates to instability along the middle to upper slopes and mass wasting, triggered by tectonic activity. The scars were further smoothed by bottom current erosion. We observe comparable acoustic stratigraphy and discordant relationships on the investigated northwestern part of Alpha Ridge. Similarly, on the central Lomonosov Ridge, Paleocene and younger sediments sampled by scientific drilling include an uppermost ~0.2 s thick drape overlying, highly reflective deposits with an angular unconformity confined to the upper slope on both sides of the ridge. Sediment instability on the three main ridges was most likely generated by a brief phase of tectonic activity (~14.5-22 Ma), coinciding with enhanced bottom circulation. These events are coeval with the initial opening of the Fram Strait. The age of the oldest sediments above acoustic basement on the Mendeleev- and west-central Alpha Ridges is estimated to be 70-75 Ma.

KW - Acoustic stratigraphy

KW - Arctic Ocean

KW - Depositional environment

KW - Inter-ridge correlation

KW - Mendeleev and Alpha Ridges

KW - Paleocirculation

KW - Tectonics

UR - http://www.scopus.com/inward/record.url?scp=78650075278&partnerID=8YFLogxK

U2 - 10.1007/s11001-010-9094-9

DO - 10.1007/s11001-010-9094-9

M3 - Journal article

AN - SCOPUS:78650075278

VL - 31

SP - 149

EP - 171

JO - Marine Geophysical Researches

JF - Marine Geophysical Researches

SN - 0025-3235

IS - 3

ER -