ISSN 0375 8192 ANTARCTIC RESEARCH CENTRE Antarctic Data Series No 25 OCEANOGRAPHY AND SEDIMENTATION BENEATH THE MCMURDO ICE SHELF IN WINDLESS BIGHT, ANTARCTICA 2005 (Revised August 2007) P.J. Barrett1, L. Carter1, D. Damiani2, G.B. Dunbar1, E. Dunker3, G. Giorgetti2, M.A. Harper1, R.M. McKay1, F. Niessen3, U. Nixdorf3, A.R. Pyne1, C. Riesselmann4, N. Robinson5, C. Hollis6 and P. Strong6 1 Antarctic Research Centre, Victoria University of Wellington, PO Box 600, Wellington, NZ. 2 Dipartimento di Scienze della Terra, Università di Siena, 8 via Laterina, Siena 52100, Italy. 3 Alfred Wegener Institut fur Polar- und Meerforschung, Columbusstrasse, Bremerhaven, Germany. 4 Department of Geological & Environmental Sciences, Stanford University, Stanford, CA 90425, USA. 5 National Institute of Water and Atmospheric Research, PO Box 14-901, Kilbirnie, Wellington, NZ. 6 Institute of Geological and Nuclear Sciences, PO Box 30-368, Lower Hutt, NZ. in association with the Antarctic Data Series No. 25 A Publication of the Antarctic Research Centre: Victoria University of Wellington PO Box 600, Wellington, New Zealand This publication is available in pdf format at our http site. http://www.victoria.ac.nz/antarctic/ Cover image: Field Camp at Windless Bight with Mt Erebus on the right. Contents Contents ....................................................................................................................................................... i Figures ........................................................................................................................................................iii Tables..........................................................................................................................................................iv ABSTRACT .................................................................................................................................................1 1 INTRODUCTION...............................................................................................................................2 1.1 References ......................................................................................................................................5 2 HOT WATER DRILLING .................................................................................................................6 2.1 Introduction...................................................................................................................................6 2.2 Site 1................................................................................................................................................7 2.3 Site 2................................................................................................................................................8 2.4 Site 3 - Sea ice mooring ................................................................................................................8 2.5 Ice shelf observations ...................................................................................................................9 2.6 References ......................................................................................................................................9 3 WATER COLUMN DATA ..............................................................................................................11 3.1 Physical oceanography from CTD data...................................................................................11 3.1.1 Site 1 data acquisition .........................................................................................................12 3.1.2 Site 2 data acquisition .........................................................................................................15 3.1.3 Site 1 results..........................................................................................................................16 3.1.3.1 Water mass structure ...................................................................................................16 3.1.3.2 Water mass variability.................................................................................................17 3.1.4 Site 2 results..........................................................................................................................17 3.1.4.1 Water mass structure ...................................................................................................17 3.1.4.2 Water mass variability.................................................................................................17 3.1.5 Comparison with J9 near the head of the Ross Ice Shelf................................................18 3.1.6 References.............................................................................................................................19 3.2 Current velocity patterns from ADCP data ............................................................................20 3.2.1 Sea ice site .............................................................................................................................20 3.2.2 Site 1 results..........................................................................................................................22 3.2.3 Site 2 results..........................................................................................................................24 3.2.4 Discussion and implications of the ADCP data ..............................................................25 3.3 Water chemistry and suspended sediment data ....................................................................27 4 SEA FLOOR DATA ..........................................................................................................................29 4.1 Sea floor sediment features from seismic data .......................................................................29 4.1.1 References.............................................................................................................................31 4.2 Sediment description..................................................................................................................32 4.2.1 Site 1 description..................................................................................................................32 4.2.2 Site 2 description..................................................................................................................35 4.3 On-site petrography ...................................................................................................................36 4.3.1 Site 1 Core 1..........................................................................................................................36 4.3.2 Site 1 Core 4..........................................................................................................................37 4.3.3 Site 2 Core 4..........................................................................................................................39 4.3.4 Clasts from Sites 1 and 2.....................................................................................................41 4.4 Sediment organic geochemistry................................................................................................44 4.4.1 References.............................................................................................................................46 4.5 Sediment ages..............................................................................................................................47 4.5.1 References.............................................................................................................................48 4.6 Sediment texture .........................................................................................................................50 4.6.1 References.............................................................................................................................53 i 4.7 Diatoms ........................................................................................................................................54 4.7.1 Methods ................................................................................................................................55 4.7.2 Results ...................................................................................................................................55 4.7.2.1 Unit A (Site 1, 0-5 cm; Site 2, 0-58 cm).......................................................................55 4.7.2.2 Unit B (Site 1, 4-36 cm; Site 2, 58-61 cm)....................................................................55 4.7.2.3 Unit C (Site 1, 36-61cm) ...............................................................................................55 4.7.3 Discussion.............................................................................................................................56 4.7.3.1 Diatom Unit A (Site 1, 0-5 cm; Site 2, 0-58 cm).........................................................56 4.7.3.2 Diatom Unit B. (Site 1, 5-36 cm; Site 2, 58-61 cm) ....................................................58 4.7.3.3 Diatom Unit C. (Site 1, 36-61 cm) ...............................................................................58 4.7.4 Comparison of Sites 1 and 2...............................................................................................59 4.7.5 Diatoms in water column compared with core tops. .....................................................59