(Table 1) Description of structures in cores at DSDP Holes 59-451, 59-448A and 59-447A

Fifteen lengths of Leg 59 cores (primarily from Hole 451 as well as from Holes 447A and 448A) exhibiting macroscopic faults were selected by Dr. R. B. Scott (Co-Chief Scientist, Leg 59) to help us initiate this petrofabric analysis. We proposed to (1) determine what dynamically useful deformation features might be associated with the faults, and (2) infer from these features as much as possible about the physical environment of the deformation (effective pressure, differential stress, temperature, and strain rate), the orientation and relatively magnitudes of the principal stresses at the time of deformation, and the degree of induration of the rocks at the time of deformation. The cores, mainly from Hole 451, had been slabbed on board ship with respect to the trace of bedding so that each cut surface contains the true bedding dip-direction. In general, the cores from Hole 451 are largely calcareous, lithic and vitric, brecciated tuffs, whereas those from Holes 447A and 448A are basalts or basalt breccias.

Mineralogy at DSDP Legs 58-60

Sediments recovered by drilling during Legs 58, 59, and 60 in the North and South Philippine Sea have been analyzed by X-ray diffractometry. The CaCO3 content was measured separately. The sites encompass several volcanic ridges and intervening inter-arc basin troughs as well as sites on the Mariana arc fore-arc sediment prism and the Mariana Trench. The sediments at all sites received major volcanogenic input from the various arcs; they tend to be rich in volcanic glass, with associated quartz, feldspar, pyroxenes and amphibole. Carbonate is a major component only at Site 445 at the southern end of the Daito Ridge, and at Site 448 on the Palau-Kyushu Ridge. All other sites were either deep relative to the carbonate compensation depth or had very high non-carbonate sedimentation rates. Clay minerals are mainly smectite and illite with lesser variable proportions of chlorite and kaolinite. Smectite predominates over illite except at sites in the Shikoku Basin and the Daito Ridge, and at one site in the Mariana Trench. At several sites, smectite increases and illite decreases with depth. Principal zeolites are phillipsite and clinoptilolite. Analcime occurs in some samples.