(Table 1) Water-extractable and acid-extractable carbohydrates in DSDP Leg 65 samples

Selected parts of ten frozen core samples from Holes 482A, 482B, 483A, and 485A, Leg 65 of the Deep Sea Drilling Project (DSDP), were analyzed for residual carbohydrates in order to determine the provenance and history of the organic material in the sediments. The samples, which represented silty-clay, shale, and nannofossil- chalk sediments, were analyzed for water-soluble monosaccharides, acid-soluble monosaccharides, and for starch and cellulose. Most samples yielded positive results for acid-extractable (polymeric) arabinose, fucose, xylose, mannose, galactose, and glucose. Amylose was detected in seven of the samples, whereas cellulose was found in only one. Possible explanations for the relatively high levels of free sugars are suggested in the conclusions to this chapter.

Grain-size distribution of sediments from DSDP Leg 65 Holes

The grain-size distribution of 223 unconsolidated sediment samples from four DSDP sites at the mouth of the Gulf of California was determined using sieve and pipette techniques. Shepard's (1954) and Inman's (1952) classification schemes were used for all samples. Most of the sediments are hemipelagic with minor turbidites of terrigenous origin. Sediment texture ranges from silty sand to silty clay. On the basis of grain-size parameters, the sediments can be divided into the following groups: (1) poorly to very poorly sorted coarse and medium sand; and (2) poorly to very poorly sorted fine to very fine sand and clay.

Oxygen and hydrogen isotopes at DSDP Leg 65 Holes

In order to provide information on the degree of alteration of the very young basaltic basement drilled on Leg 65 in the mouth of the Gulf of California, we have measured the oxygen isotopic composition of whole rocks and mineral separates. Considerable data already exist for older ocean crust, in particular for the deep holes drilled in the Atlantic Ocean on Deep Sea Drilling Project (DSDP) Legs 37, 45, 46, and 51-53. These data indicate that in all of these holes, which include crust as young as 3.5 m.y. old, a significant amount of alteration has taken place as the result of low-temperature interaction between basalt and seawater (cf. Muehlenbachs, 1977, 1980; Hoernes et al., 1978; Friedrichsen and Hoernes, 1980). It is therefore of interest to determine whether Leg 65 crust, which is only 0.5 to 1.5 m.y. old, has experienced a similar degree of alteration.

Composition of post-Jurassic deposits from the Northwest Pacific and the Galapagos Rift, data of DSDP Legs 62, 65, and 70

The monogragh contains results of mineralogicai and geochemical studies of Mesozoic and Cenozoic deposits from the Pacific Ocean collected during Deep Sea Drilling Project. Special attention is paid on the aspects of geochemical history of post-Jurassic sedimentation in the central part of the Northwest Pacific, detailed characteristics of the main stages of sedimentary evolution are given: Early Cretaceons (protooceanic), Late Cretaceons (transitional) and Cenozoic (oceanic). Results of mineralogical and geochemical studies of hydrothermal deposits from the Galapagos Rift are given as well.

Rock magnetism and paleomagnetism of basalts at DSDP Leg 65 Holes

We investigated the magnetic and paleomagnetic properties of 77 basalt samples from Holes 482, 482C, 482D, 483, 483B, 485, and 485A in order to study the structure and development of the ocean's crust. During the course of this study, we measured the natural remanent magnetization, Jn, and its stability in an alternating magnetic field; the magnetic susceptibility, x; the saturation magnetization, Js; the saturation remanent magnetization, Jrs; the coercivity of maximum remanence, HCR; and the median destructive fields MDFn (for Jn) and MDFs for Jrs. A thermomagnetic analysis for Js and Jrs was also performed; these latter measurements were made on the same samples.

Geochemistry and minerals at DSDP Leg 65 Holes

Petrologic studies of mid-ocean ridge basalt (MORB) (e.g., Melson et al., 1975; Flower, et al., 1977; Byerly and Wright, 1978; Melson, 1979; Byerly and Sinton, 1980; Thompson, 1980) show that magmatic liquid-fraction trends are indicated by the compositions of fresh glass selvedges, usually, but not always, associated with pillow basalts. In contrast, whole-rock compositional variation will often reflect the complicating effects of syn- and post-eruptive phenocryst accumulation. Additional variation may be introduced by the reaction of basalts with seawater. While comparatively severe alteration of variable type was noted locally in the young basalts recovered across the mouth of the Gulf of California on Leg 65, most of the basalts were extremely fresh, making them ideal for studies of compositional variation.