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doi:10.2204/iodp.proc.317.209.2015

Materials and methods

Sediments from Holes U1354B (44°50.8367′S, 171°47.2069′E) and U1354C (44°50.8487′S, 171°47.2080′E), drilled on the outer shelf at a water depth of 113.4 m off the South Island of New Zealand, are mainly composed of silt, sandy mud, and muddy sand intercalated with thin fine- to medium-grained sands and/or shell hash beds. In this study, the section shallower than 375.0 mbsf was examined. Recovery of sediments between 0 and 173.9 mbsf was ~90%, but below this depth, recovery was poor. Sedimentation rates in the cores were calculated based on bio- and magnetostratigraphy as follows (Expedition 317 Scientists, 2011a): 21 cm/ky above 75 mbsf, 9.3 cm/ky between 75 and 128 mbsf, 4.5 cm/ky between 128 and 190 mbsf, and 40 cm/ky below 190 mbsf. Based on these sedimentation rates, the 144 samples with an average sedimentation rate of 30 cm/ky were taken from horizons above 375.0 mbsf. Of these, samples with sedimentation rates <22 cm/ky were examined between 0.3 and 165.7 mbsf. Furthermore, near-seafloor samples from Holes U1353B (44°46.1203′S, 171°40.4407′E; 0.9 mbsf), U1351A (44°53.0307′S, 171°50.4037′E; 0.3 mbsf), U1351B (44°53.0422′S, 171°50.4065′E; 0.9 mbsf), and U1352B (44°56.2558′S, 172°1.3630′E; 0.2 mbsf) were also examined to reveal recent ostracode assemblages in the study area. Samples collected using a 10 cm³ cylinder (diameter = 2 cm) were freeze-dried and weighed (dry weight varied from 13.21 to 33.46 g) prior to wet sieving through a 63 µm sieve. The residues were dried, weighed, and divided into workable aliquots with a sample splitter until a fraction containing a minimum of 200 specimens was obtained. In samples where 200 ostracode specimens were not achieved, all ostracodes were counted. The resulting residue was then sieved through a 125 µm sieve, and all ostracodes retained on the sieve were picked. Both valve and carapace were counted as one specimen.

To reconstruct the faunal character of the section, we calculated the species diversity and equitability for samples containing more than 50 specimens. The species diversity is given by H(S) (Spellerberg and Fedor, 2003):

where p_i is the proportion of specimens of ith species and H(S) is the species diversity.

The equitability (E q.) of Buzas and Gibson (1969) is as follows:

where S is the number of species.

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