Supplemental Smear Slides, Site C0002, Hole B
During Expedition 338, Cores 49R through 66R, obtained during Expedition 315 (Expedition 315
Scientists, 2009), were examined twice by the Science Party, once by Group A and once by Group A and
B together during the cross-over period. These cores were of particular interest because they contain the
lower part of Unit III and the entirety of the Unit IV materials cored in Hole B (Expedition 315), an
interval that partially overlaps the interval sampled by cuttings in Hole F and by coring in Holes H and J
(Expedition 338). The Unit III/IV boundary was defined in part by biostratigraphic data (Expedition 315
Scientists, 2009) indicating an unconformity (3.65 Ma to 5.01-5.12 Ma) occurring between Core 48R CC
and Core 49R CC (916.95-923.8 mbsf). The specific location of the unconformity within the 4 core
sections representing that interval (section 49R 3 being an IW sample) was not identified during
Expedition 315.
Based upon careful visual inspection of the color, texture, and ichnofauna, it was the assessment
of the Expedition 338 Sedimentology team that the unconformity may occur at a sharp, but otherwise
nondescript boundary in Section 49R 4 24 cm (approx 922.5 mbsf). To test this hypothesis, two smear
slides and two small samples for biostratigraphy (to be analyzed by on-shore scientists) were taken at 49R
4 22 cm and 49R 4 25 cm. Smear slide observation confirms that the sample at 22 cm is more carbonaterich than the one at 25 cm (more nannofossils), but the one at 25 cm still contains more carbonate than is
generally typical of Unit IV (around 0.1 wt. percent by XRD in most samples, Expedition 315 Lithology
section, Table T6).The two uppermost XRD samples in Unit IV (315 Lithology table T5), however,
contain 9.5 and 22.6 percent calcite, so a carbonate-bearing sample in the upper part of Unit IV is not
unexpected. Confirmation of the position of the unconformity awaits the biostratigraphic results.
Seven additional smear slides were taken for training purposes and for testing the composition of minor
lithologies (Table 1). Most thin beds are quartzo-feldspathic very fine sand or sandy silt, but one fine ash
was identified (65R2, 42 cm), suggesting that small ash layers are more abundant in Unit IV than was
recorded in on the original VCDs.
Oxidation of unstable sulfide minerals to produce jarosite (a fuzzy yellowish efflorescence
particularly visible in sandy/silty intervals) and gypsum (Figure 1) are notable alterations that have
developed within the core over the five years since it was taken.
Figure 1.Gypsum crystals (white to translucent, with classic swallow-tail shape) decorating the surface of
silty mudstone at 52R1 19-20 cm.
Reference
Expedition 315 Scientists, 2009. Expedition 315 Site C0002. In Kinoshita, M., Tobin, H., Ashi, J.,
Kimura, G., Lallemant, S., Screaton, E.J., Curewitz, D., Masago, H., Moe, K.T., and the Expedition
314/315/316 Scientists, Proc. IODP, 314/315/316: Washington, DC (Integrated Ocean Drilling
Program Management International, Inc.). doi:10.2204/iodp.proc.314315316.124.2009