Natural gamma-ray activity (NGR), magnetic susceptibility, and gamma-ray attenuation porosity evaluator (GRAPE) density were measured on whole-round samples (see "Physical Properties" in the "Explanatory Notes" chapter). Because of the low recovery at the shelf sites (Sites 1100, 1102, and 1103), only a few cores were available for MST measurement. At Site 1100, all the MST measurements were made on one core (Core 178-1100C-1R). No measurements were made from Site 1102. At Site 1103, GRAPE density, magnetic susceptibility, and NGR activity were measured from 247.33 to 355.80 mbsf (Cores 178-1103A-27R through 38R). No P-wave measurements were made on the cores because of the many air gaps in the whole-core sections.
Whole-core magnetic susceptibility was measured at 2-cm intervals (averaged over 2 s). The raw data for Site 1100 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F19. Limited recovery in the upper sections of other shelf sites renders comparison impossible. The raw data for Site 1103 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F20. The data show no discernibly consistent relationship with the described sediment column (see "Lithostratigraphy" and discussion below).
Density was measured by gamma-ray attenuation at 2-cm intervals (averaged over 2 s at each point). The raw data for Site 1100 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F19. Again, limited recovery in the upper sections of other shelf sites renders comparison impossible. The raw data for Site 1103 (on CD-ROM and the World Wide Web [see "Related Leg Data" in the Table of Contents]); Fig. F20) show no obvious correlation with lithostratigraphic variation.
The raw data for Site 1100 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F19. Limited recovery in the upper sections of other shelf sites renders comparison impossible.
Whole-core NGR emissions (averaged over 15 s) were counted at 15-cm intervals. The raw data for Site 1100 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F19. The raw data for Site 1103 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F20. The data show no obvious correlation with lithostratigraphic variation.
In the absence of a continuous record and any obvious downhole correlation between the MST data sets and the lithostratigraphy, the data were cross-plotted by facies to determine whether relationships existed. Cross plots of magnetic susceptibility and NGR data for the upper and lower diamicts are shown in Figure F21A. From the plot it can be seen that the diamict sequences between 246 and 286 mbsf (upper diamict) and 304 and 321 mbsf (lower diamict) form two distinct populations. This may suggest that the diamicts are derived from different source materials or may reflect the differences in grain size or packing between the two materials. Smear-slide analysis (see "Site 1103 Smear Slides") shows that the clay and silt contents in the matrix of the upper diamict average ~67.6% and 37.2%, respectively; in the lower diamict, the values are 29% and 15%. Low clay and silt contents in the lower diamict might be expected to reduce the NGR and susceptibility signals. However, the other nondiamict lithofacies form clusters of values in susceptibility-NGR space (Fig. F21A, F21B), with no consistent relationship with grain size. The sands and gravels show two populations (not size dependent), which are coincident with the upper diamict and the laminated sediments.
Gravimetric and volumetric determinations of index properties were made for two samples from each of Holes 1100C and 1100D and 18 samples from Hole 1103A. One sample was taken from Hole 1103A every first and third section per core, where possible. Wet mass, dry mass, and dry volume were measured, and from these measurements, percentage water weight, porosity, dry density, bulk density, and grain density were calculated (see "Physical Properties" in the "Explanatory Notes" chapter). The raw data for Site 1100 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F22. The raw data for Site 1103 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are presented in Figure F23.
Bulk density for Site 1103 correlates well with GRAPE density (Fig. F23A), although the two measurements of density are offset as at other sites. This offset shows a slight decrease with depth, which may reflect the effects of lithology and compaction on core disturbance.
Porosity values at Site 1103 show a pattern similar to that at Site 1097. The diamicts between 245 and 285 mbsf show a porosity of ~20% (Fig. F23B), ~10%-15% lower than the laminated sediments directly below them. The diamicts between 300 and 320 mbsf show no drop in porosity and are 5%- 15% more porous than the diamicts 15 m higher in the sequence. Porosity is related to sediment sorting, cementation, and the stress history of the sediments. The lower levels of clay and silts in the lower diamict (see "Lithostratigraphy") suggest that they are better sorted and may maintain a higher porosity under stress (horizontal or vertical). Thin-section analysis ("Micromorphology") also suggests cementation in the sediments, although there is little difference between the upper and lower diamicts. Alternatively, the upper material may have undergone shear or overburden compaction to a greater extent than the lower material (see "Lithostratigraphy" and "Physical Properties", both in the "Site 1097" chapter, for further details). However, if the porosity is shear dependent, this shear cannot have occurred in a turbulent debris flow, as the open upper surface would have ensured mixing. Any shear reduction must therefore be a subglacial relic that survived in a plug-flow mass movement, or imply plug-flow layers within any debris flow (to have prevented turbulence).
Discrete P-wave velocity measurements were made on cores of Sites 1100 and 1103 for the depth interval 0-3.5 mbsf (Site 1100) and 75-355 mbsf (Site 1103) using the Hamilton Frame sensor pair (PWS3) of the velocity-strength system. All measurements were done using single unfractured matrix or matrix-supported pieces placed directly (without the liner) between the Hamilton Frame heads. The data for Site 1100 (five values) are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents). The data for Site 1103 are provided on CD-ROM and the World Wide Web (see "Related Leg Data" in the Table of Contents), and are given in Figure F24.
The low recovery zone (0-240 mbsf) of Site 1103 is covered by only nine data values, one of which is from a granite clast. With the exception of the clast, the velocities vary between 1760 and 2660 m/s. In Cores 178-1103A-27R through 38R (247-355 mbsf), the data coverage is much better, with an average spatial resolution of 2.3 m. The lower lithified part of the site shows P-wave velocities between 2000 and 3700 m/s. The diamictite layers with pebble size clasts (3000-3500 m/s) contrast sharply in P-wave velocity with the poorly sorted sandy units (2000-2700 m/s).
Although measurements from Site 1100 samples are limited, they provide the only direct P-wave velocity information collected near the seafloor for all shelf sites.
Samples were taken from Cores 178-1103A-28R and 34R for impregnated thin-section analysis to determine the structural composition of the diamicts and their response to their stress history. The latter often gives information on the physical properties of the sediment in the past.
Sample 178-1103A-28R-1, 85 cm, is a sand-rich (40% sand) diamict that contains a lens of fines, matching the lithostratigraphic assignment of the material as a stratified matrix-supported diamict. The fines and diamict all show a strong grain alignment at 10º from the horizontal, which suggests shear after the materials were deposited. Such a morphology may indicate subglacial deposition and shear. The alternative, matching the lithostratigraphic interpretation, is that the materials were deposited as flow bodies (presumably at the angle of repose) and were then reactivated at some later point as a whole unit.
Sample 178-1103A-28R-2, 27 cm, is a less sand-rich material (15% sands) than that above, with a subhorizontal grain fabric and bands of stronger alignment suggesting subhorizontal shear. This fabric was then disrupted by low-strain shear zones mirrored at ~30º around the horizontal and bands of fines in the same directions. These later fabrics probably indicate subhorizontal compression and dewatering, which might be expected in both flow deposits and a clast-rich diamict (where material can be trapped in a pure shear geometry between clasts).
Thus, the micromorphology of Core 178-1103A-28R gives only ambiguous evidence for the origin of the material. The material also shows moderate iron mineral precipitation, which may explain the low porosity of the sediments (see discussion above).
Sample 178-1103A-34R-1, 107 cm (Fig. F25), was taken across the boundary between a thick diamict and a thin (<3 cm thick) clay-rich bed. The thin section suggests that the diamict is at least partially composed of reworked diamicts from two sources with different levels of iron staining and silt. Rounded clay intraclasts were incorporated into the diamict from the clay layer, and the boundary with the clay layer is pervasively mixed over a distance of ~75 µm. This mixing morphology probably indicates a low effective pressure ("fluid" conditions) and an unconfined, high-energy mixing environment. After the material was mixed, it gained a fabric in two directions. First, the material pervasively aligned at 48º (dipping right in the slide), and then numerous shears formed at 25º (dipping left).
Several of these shears can be traced into the remnants of the clay layer where they join the Riedel shears of a principal displacement zone (PDZ). The PDZ shows a lensed, infinite shear geometry and dips left at 10º. Although the true dip angles are unknown, it is highly likely that the initial pervasive fabric alignment was in the thrust shear direction of the PDZ and formed during the early shearing of the material. Such a development is strongly suggestive of material that has not been overconsolidated (Tchalenko, 1968), which suggests that the diamict had lost any subglacial overconsolidation signature before the shear event.
Where the clays are in a single body or in the form of a large intraclast, they display a remnant domainal fabric in patches at various high angles to the initial pervasive reorientation at 48º (dipping right). Strong domainal fabrics have not been found in subglacial materials or subglacially reworked materials, and the fabric is strongly suggestive of marine material that has not been subjected to subglacial conditions. Thus, the stress response and general micromorphology of the material backs a mass flow reworked origin for the diamict in Core 178-1103A-34R (see "Lithostratigraphy").