Basement was encountered in Hole 1149B at a depth of 407.77 mbsf, in Hole 1149C at 398.41 mbsf, and in Hole 1149D at 300.46 mbsf. A total of 195.96 m of basement was cored during Leg 185 at Site 1149. In Hole 1149B, 37.43 m was cored (Cores 185-1149B-29R through 32R) with an average recovery of 22.71%; in Hole 1149C, 28.29 m was cored (Cores 185-1149C-9R through 11R) with an average recovery of 13.68%; and in Hole 1149D, 130.24 m was cored (Cores 185-1149D-5R through 19R) with an average recovery of 19.64% (Fig. F32A, F32B, F32C; Table T5; also see "Site 1149 Vein Log," also in ASCII format). Recovery was lower at this site than at Site 801, perhaps because the cored interval consisted dominantly of thin, fractured flows, pillow basalts, and breccia.
The basement rocks recovered from Holes 1149B and 1149C are all aphyric basalts. Minor amounts of plagioclase and olivine (<1%) were observed as phenocryst phases, but they were not abundant enough to permit the addition of a mineral modifier to the rock name. The aphyric basalts include a mixture of thin (<50 cm) pillows and some intermediate thickness (50 cm to 1 m) cooling units that could represent either pillows or flows. There were a few thicker cooling units (up to 2.88 m) in Hole 1149D, described as flows in Figure F32C and Table T5. However, the pieces recovered were highly fractured, and the flows could not be described as massive. In addition, several intervals of breccia and a few of interpillow sediment were recovered.
Basement lithologic units are numbered beginning with Unit 1. Holes 1149B and 1149C contain a single lithologic unit, Unit 1, that contains several subunits of breccias and individual cooling units. Unit 1 has 15 subunits in Hole 1149B and six subunits in Hole 1149C. In Hole 1149D, six lithologic units were identified. In Hole 1149D, Unit 1 consists of a single piece with a significantly higher olivine content, which was not observed in Holes 1149B or 1149C. Units 2-6 in Hole 1149D all contain subunits or cooling units. The subunits are identified on the basis of chilled or glassy contacts, fining of grain size toward the margins of pillows or flows and presence of breccia or hyaloclastite. Thin intervals of sediment or interpillow material and breccia are noted as boundaries between subunits, whereas thicker intervals (>5-10 cm) are distinguished as individual subunits.
The basement stratigraphic logs (Table T5; also see "Site 1149 Vein Log," also in ASCII format) include all the igneous core description data for Leg 185 Holes 1149B, 1149C, and 1149D: unit or subunit number, depth, interval thickness, lithology, texture, structure, color, presence or absence of chilled margins, comments, and the location of shipboard samples. The basement stratigraphy for Holes 1149B, 1149C, and 1149D is plotted in Figure F32A, F32B, and F32C. The following section summarizes the most important characteristics of lithologic subunits from Holes 1149B, 1149C, and 1149D.
Unit 1, in Holes 1149B and 1149C, consists of aphyric basalt pillows or thin flows. The contact between the overlying sediments and basement consists of a 0.78-m brecciated zone in Hole 1149B. There appears to have been some reaction between pink carbonate-bearing sediments and the basalt in this interval. The contacts between individual basalt pieces and the sediment are wavy and irregular with pronounced red iron staining. The sediment also appears to have been baked. The contact between the sediment and basement was not recovered in Holes 1149C or 1149D. The last few pieces of sedimentary material recovered in Sample 185-1149C-9R-1, 0-51 cm, and Sample 185-1149D-5R-1, 0-16 cm, are mainly chert (see "Unit IV"); the remaining pieces recovered in both holes are basalts.
The basalt in Unit 1 from both Holes 1149B and 1149C is highly altered and reddish gray in color with pronounced dark bluish gray alteration halos. Minor amounts of vesicles are present throughout Unit 1, their abundance varying between <1% and 3%. Several chilled pillow rims occur within Unit 1 (see Figs. F33, F34), and these define the individual pillows or cooling units, as noted in Table T5. In Hole 1149D, the units were assigned on the basis of mineralogical observations (see "Petrology"). Units 2, 3, and 6 contain larger phenocrysts; Unit 2 also contains crystal clusters or microphenocrysts that were no longer observed in Unit 3. Unit 4 contains more altered and finer grained basalts with the lowest abundance of phenocrysts, and Unit 6 contains the highest abundance of olivine phenocrysts.
In Hole 1149B four subunits contain breccias (Fig. F35); in Hole 1149C one breccia subunit is present (Fig. F36). Breccias in all three holes have a carbonate or greenish clay cement, with the exception of the first breccia in Hole 1149B, where sediment is also present in the cement. For the most part, the basalt clasts are subangular to angular and vary in size from 5 to 20 cm. Some microbreccia is present in Hole 1149D (e.g., interval 185-1149D-11R-2, 104-120 cm) (Fig. F37). Thin intervals of hyaloclastite with altered glassy shards occur along pillow rims. A spectacular example of the hyaloclastite is present in Sample 185-1149D-7R-1, 29-42 cm (see Fig. F38). Some of the hyaloclastite intervals (e.g., Hole 1149B, Subunits 1-12, and Hole 1149D, Subunits 4-5), however, contain highly altered, rounded glassy clasts (see Figs. F34, F39). Interpillow material is rare at Site 1149 but not absent, (e.g., see interval 185-1149D-11R-2, 104-120 cm (Fig. F40). Fresh glass is present but not particularly common at Site 1149 (see Table T6).
Basement was penetrated in Core 185-1149B-29R, at a depth of 407.77 mbsf, in Core 185-1149C-9R, at 398.41 mbsf, and in Core 185-1149D-5R, at 300.46 mbsf. All basement rocks recovered in Holes 1149B and 1149C are assigned to the same basement lithologic unit, Unit 1. In Hole 1149D six lithologic units are identified. All three holes consist of aphyric basalt pillows or thin flows similar to those encountered in Hole 801C. Several interpillow breccia intervals are also present. The basalt is highly altered, reddish gray in color, and has pronounced dark blue-gray alteration halos. Minor amounts of plagioclase and olivine phenocrysts and small vesicles are present throughout.