Three different methods were used to recover sediment cores in 2010. The upper 0.8 m of sediments were recovered using a freeze-coring technique (Renberg and Hansson, 1993). This core recovers a thin (approximately 1 cm) vertical slab of relatively undisturbed sediment and was only used for correlation purposes. The freezing technique physically disturbs the micro-structure of unconsolidated sediments and paleomagnetic sub-samples were not obtained from it. Five cores for paleomagnetic measurements were recovered using a rod-operated fixed-piston corer described by Snowball and Sandgren (2002). This system recovers complete 4.8 m long cores of sediment in PVC tubes of either 60 or 63 mm internal diameter, although it is not oriented to a geographic azimuth for practical reasons. This system provided four overlapping cores for paleomagnetic reconstructions to a sediment depth of 8 m (GD0a, GP1, GP2 and GP4. GP3 failed due to an insecure piston). A cable operated Uwitec “Niederreiter” percussion piston corer (three metre long drives) was subsequently used to recover sediments to depth of approximately 11.8 m (drives GD1–GD4). Sandy sediment was recovered in the bottom of GD4, equivalent to a sediment depth between 11.8 m and 11.5 m and it proved impossible to penetrate through this material with the available equipment.
sediments
upper 0.8 m
m
vertical slab of relatively undisturbed sediment
thin
approximately 1 cm
cm
cores
Five
cores of sediment
long
4.8 m
m
PVC tubes
internal diameter
60 or 63 mm
mm
overlapping cores
four
sediment
depth
8 m
m
drives
long
three metre
metre
sediments
depth
approximately 11.8 m
m
sediment
depth
between 11.8 m and 11.5 m
m