Physical properties at Site 1210 were measured on both whole-round sections and discrete samples from split-core sections. Continuous whole-round measurements were made of magnetic susceptibility, GRA bulk density, and compressional P-wave velocity, using the MST for all Site 1210 cores. Whole-round sections of Hole 1210A cores were also measured for natural gamma radiation using the MST. Discrete measurements of compressional P-wave velocity were made at a frequency of at least one measurement per split-core section in Holes 1210A and 1210B. Index properties were measured on discrete samples from split-core sections at a frequency of one measurement per section throughout Hole 1210A and in Cores 198-1210B-26H to 42H.
All core sections from Holes 1210A and 1210B were routinely measured on the MST for magnetic susceptibility and GRA density at 3-cm intervals (Figs. F28, F29). MST P-wave velocity was also routinely measured at 10-cm intervals in all cores from the two holes (Fig. F30). Natural gamma radiation was measured on the MST at 30-cm intervals in Hole 1210A cores only (Fig. F31). All collected MST data are archived in the ODP Janus database.
Magnetic susceptibility values (Fig. F28) are generally highest in the uppermost ~116 m of the Site 1210 sedimentary column (lithologic Unit I; see "Lithologic Unit I" in "Lithostratigraphy"). The relatively lower magnetic susceptibility values in the sediments below ~116 mbsf occur within lithologic Unit II, which has higher carbonate contents. Peaks in magnetic susceptibility in lithologic Subunits IA and IB may correlate with distinctive ash layers (see "Lithologic Unit I" in "Lithostratigraphy"). In the middle Pleistocene-Miocene section an excellent correlation is observed between magnetic susceptibility and color reflectance data, primarily the total reflectance value (L*) and the 550-nm wavelength (see "Lithologic Unit I" in "Lithostratigraphy"). Both magnetic susceptibility and color reflectance data in this interval reveal a pronounced cyclicity, which will be useful in identifying astronomically controlled depositional processes. Magnetic susceptibility values are generally higher in lithologic Subunit IC, relative to Subunit IB. As already observed at Site 1209, a small downhole increase in magnetic susceptibility (at ~112.8 mbsf) characterizes the middle Miocene/lower Oligocene unconformity at Site 1210 (see "Biostratigraphy"). Miocene lithologic Subunit IC and Paleocene-Oligocene lithologic Unit II are generally characterized by fairly constant magnetic susceptibility values. Small-magnitude peaks in magnetic susceptibility occur within Unit II (e.g., at ~198 mbsf) (see "Principal Results"). The K/T boundary is marked in Holes 1210A and 1210B by a large peak in magnetic susceptibility values, associated with an increase in clay content (see "Organic Geochemistry"). In lithologic Unit III, magnetic susceptibility values are generally close to background, except for some short-lived excursions that are related to chert horizons, and do not exhibit any consistent downhole variation.
MST GRA bulk density data exhibit a general downhole increase in magnitude in the upper 115 m of the sediment column (Fig. F29), resulting from sediment compaction and dewatering processes with increased overburden pressure. GRA bulk density data also show distinct variations that relate to lithologic changes at distinct horizons, for example the middle Miocene/lower Oligocene unconformity and the Cretaceous/Paleogene boundary. Cyclic variation in GRA bulk density values, similar to that evident in magnetic susceptibility and color data (see "Lithologic Unit I" in "Lithostratigraphy"), is found within Pleistocene-Pliocene lithologic Subunits IA and IB. Lithologic Subunit IC (~112 to ~116 mbsf) is characterized by higher GRA bulk density values. GRA bulk density values also display rhythmic changes between ~116 and ~220 mbsf that are related to cyclic variations in sediment composition, such as carbonate content (see "Organic Geochemistry").
GRA bulk density values are consistently higher than the discrete wet bulk density measurements (Fig. F29; Table T14) throughout Hole 1210A and Hole 1210B. These overestimated GRA bulk density values can be explained by the relatively high carbonate content, porosity, and water content of sediments; the calibration procedure for the MST GRA sensor is optimized for mixed-lithology sediments. Consequently, the GRA method overestimates the density in carbonate-rich sediments. This phenomenon is most pronounced in lithologic Unit III because these sediments have the highest carbonate contents (see "Organic Geochemistry").
MST P-wave velocities were recorded at 10-cm intervals in Holes 1210A and 1210B (Fig. F30). Despite some obviously "out of range" values, a general trend to higher velocities with increased depth in the sediment column can be discerned from values lying between ~1500 and ~1600 m/s. MST P-wave values generally increase with depth through lithologic Unit I and the upper half of Unit II from 0 to ~150 mbsf, whereas they decrease downhole from ~150 to ~215 mbsf. Between ~110 and ~120 mbsf, P-wave values increase relatively abruptly from ~1525 to ~1550 m/s. At ~220 mbsf there is a relatively abrupt increase in P-wave velocity that is associated with the K/T boundary and the boundary between lithologic Units II and III. In lithologic Unit III, MST P-wave values maintain an almost constant velocity of ~1550 m/s. The downhole trend recorded by the reliable MST P-wave logger (PWL) values also compare well with the discrete measurements of P-wave velocity (see Table T15; Fig. F32). However, MST PWL values are consistently lower than discrete values (most pronounced in the Paleocene and upper Maastrichtian sediments); this difference may be due to the assumption in the calibration of the MST PWL that the core liner is full of sediment and that there is no water between the liner and the sediment.
Natural gamma radiation data were collected at 30-cm intervals on cores from Hole 1210A only (Fig. F31). Peak natural gamma radiation values occur at the middle Miocene-lower Oligocene unconformity and in upper Eocene and upper Paleocene sediments; high values indicate small increases in clay content in the sedimentary record (see "Lithologic Unit I" and "Lithologic Unit II" in "Lithostratigraphy"). Below 135 mbsf, natural gamma radiation values remain generally constant with increase in burial depth.
Discrete measurements of compressional P-wave velocity were made on Site 1210 split-core sections using the modified Hamilton frame (PWS3) velocimeter. These data are listed in Table T15 and illustrated in Figure F32. Data were collected at a routine sampling frequency of one measurement per section. Velocities vary between ~1520 m/s in the soft surface sediments and ~1570 m/s in the more consolidated sediments. Discrete P-wave measurements show a general downhole increase in velocity between 0 and ~380 mbsf, which is similar to that evident in the reliable data obtained with the MST PWL. The lack of evidence for early diagenetic cementation near the seafloor, as shown by high-percentage porosity in the interval 0-100 mbsf (Fig. F33; Table T14), suggests that increasing P-wave velocity with depth in the upper 100 m of the sedimentary column is primarily the consequence of compaction and pore fluid expulsion. An increase in discrete P-wave velocities between 0 and ~120 mbsf broadly correlates with an increase in the magnitude of discrete bulk density values (Fig. F33). P-wave values then exhibit an abrupt increase between ~100 and ~120 mbsf, from ~1520 to ~1570 m/s. P-wave velocities between ~120 and 380 mbsf remain relatively constant at a value of ~1570 m/s. Recorded P-wave velocities in the upper part of lithologic Unit III are slower than those measured at the base of this sedimentary interval; this variation may be due to increased lithification of the Cretaceous sediments with greater burial depth.
Index properties were determined for discrete samples from Hole 1210A and Cores 198-1210B-26H to 42H. These data are listed in Table T14 and shown in Figures F34 and F35. Index properties primarily reflect progressive sediment compaction and fluid expulsion with depth in the sediment column, but also indicate changes in sediment composition as defined by lithologic units and subunits (see "Lithostratigraphy"). Bulk and dry density increase in magnitude between the seafloor and ~120 mbsf, within lithologic Unit I. Bulk and dry density continue to increase to maximum values at ~210 mbsf in lithologic Unit II. Between 220 and ~300 mbsf, both bulk and dry density generally decrease. By comparison, grain density exhibits a small general downhole decrease in magnitude from 0 to ~380 mbsf. Water content, porosity, and void ratio all exhibit a general downhole decrease between the seafloor and ~180 mbsf, within lithologic Unit I (Pleistocene-Oligocene) and the Eocene portion of Unit II. Water content, porosity, and void ratio increase slightly between ~180 and ~270 mbsf, within the Paleocene portion of lithologic Unit II and upper part of lithologic Unit III (Cretaceous). These trends suggest that overburden on the Cretaceous sediments was not sufficient to cause significant downhole water loss and decrease in porosity.
Physical properties data at Site 1210 show variation with depth below seafloor that suggests control by progressive compaction and fluid expulsion in the upper ~180 m. As at Site 1209, a simple relationship between lithology and physical properties is less obvious than at Sites 1207 and 1208. The absence of such a relationship may in part be due to the more continuous Late Cretaceous-Holocene sedimentation at Site 1210 and, hence, the absence of major unconformities spanning long periods of geologic time. As for Site 1209, the unusual physical properties data from below ~180 mbsf cannot be explained only by the sediment burial history. The physical properties data suggest that there has been less diagenesis and compaction in the sediments below 180 mbsf, relative to those in the interval ~95-180 mbsf. This may be a reflection of varying microfossil composition within the Site 1210 sediments and the so-called "diagenetic potential" of different sediments (see "Physical Properties" in the "Site 1209" chapter).