At Site 1202, ~760 m of sediment was obtained from four holes. Holes 1202A, 1202B, 1202C, and the upper part of Hole 1202D were drilled using the advanced piston corer (APC), whereas the lower part of Hole 1202D was drilled using the extended core barrel (XCB) (Fig. F3). Because of time constraints, only the interval between 0 and 140 mbsf was run on the multisensor track (MST) during Leg 195, whereas the lower section between 140 and 410 mbsf in Hole 1202D was run during Leg 196. The MST measured three physical property parameters: density, magnetic susceptibility, and P-wave velocity. A comparison of the bulk density measurements made during Legs 195 and 196 on samples from Hole 1202D suggests that the measurements made during Leg 196 were not reliable. The Leg 196 bulk density values were 0.3–0.5 g/cm3 lower than the Leg 195 measurements for the same depths (0–140 mbsf), due to desiccation and/or pooling of water (Shipboard Scientific Party, 2002). Aside from this, magnetic susceptibility and bulk density show good correlation among the holes on a scale of meters, but the noise caused by gas expansion voids hampered correlation at smaller scales (<1 m) and therefore precluded splicing the holes into a composite record (Shipboard Scientific Party, 2002).
The lower sections below ~130 mbsf at Site 1202 contain numerous turbidite layers. The low recovery between 220 and 280 mbsf in Hole 1202D (Fig. F3) is attributed to high sand content. To better understand the occurrence of such turbidite deposits at the site, C.-Y. Huang et al. (2005) conducted a very detailed, quantitative description of all of the cores from Hole 1202D. All visible turbidite structures, such as occurrences of silt/sand layers, grain size grading, basal erosion, cross ripples, detritus composition, and redeposited shallow-water microfossils, were noted. Detailed descriptions of individual cores from Hole 1202D are presented graphically in 41 figures (C.-Y. Huang et al., 2005). In addition, the thickness percentage of silt/sand layers in every core section is calculated and graphically summarized (Fig. F6A). The percentages of the coarse fraction (>63 µm) in the bulk sediments show very similar profiles (Fig. F6B). It is evident that turbidity current deposition was frequent at this site, particularly in the interval from 175 to 325 mbsf, and peaked between 230 and 280 mbsf (Wei et al., 2005). Only the uppermost 130 m of Holes 1202B and 1202D are free of visible silt/sand layers (C.-Y. Huang et al., 2005).
In the intervals where no sand/silt layers are intercalated, the core is composed of monotonous dark gray hemipelagic clay and fine silt-sized sediments (Salisbury, Shinohara, Richter, et al., 2002). In descending order of abundance, the clay fraction consists of illite, chlorite, kaolinite, and smectite (Diekmann et al., submitted [N1]). Microfossils such as foraminifers and radiolarians are scarce, as shown by their low percentages (<5 wt%) in the coarse fraction (>63 µm) in the uppermost 120 m (0–29 ka) of the section where no turbidites exist (Fig. F6B).
Hole 1202B was chosen as the focus for paleoceanographic and sedimentological studies because of its deep penetration and good recovery (Fig. F3). To make a complete stacked record for Site 1202, the upper section of Hole 1202D was correlated with Hole 1202B using observed lithological characteristics and physical properties by Wei et al. (2005). Similar efforts were conducted to correlate Hole 1202A with Hole 1202B in the current synthesis. As an example, Figure F4 shows the correlation lines among the three holes using volume magnetic susceptibility. Most of the correlation lines are consistent among the three sets; the most consistent are listed in Table T1, along with their assigned ages.