Introduction

Abstract

The DSDP program in the Pacific Ocean for [1973][1974] was based on the plans of the JOIDES Pacific Advisory Panel, within the operational constraints of the DSDP and the long-term objectives of the JOIDES Executive and Planning committees. The Pacific Advisory Panel had assessed a number of first-order scientific problems of broad interest to earth scientists. Topical problems and regional problems were arranged in a matrix so that many sites in the Pacific could be chosen where the highest-priority topical problems could be investigated by drilling where regional information might also be obtained. The major topical problems, not listed in any order of priority, are: (1) composition, structure, and physical properties of oceanic basement; (2) plate genesis and evolution; (3) plate motions; (4) diagenesis and geochemical evolution of sedimentary rocks; (5) structure, history, and origin of various continental margins; (6) biostratigraphy; (7) paleooceanography; and (8) geodynamics and geophysics. PROGRAM AND OBJECTIVES OF LEG 32The northwestern Pacific Ocean is the largest expanse of old oceanic lithosphere, and so the principal theme of Leg 32 set by the Pacific Advisory Panel was the late Mesozoic history of the Pacific Ocean. The main scientific goals originally set for the leg were to: 1) Determine the development of the very deep sea floor of the western Pacific, including the nature of its basement rocks and the age, lithology, and fossil content of the sedimentary rocks overlying acoustic basement. Patterns of linear magnetic anomalies that do not match the sequence of well-dated latest Cretaceous to presentday reversals are present east of Japan, west of the Hawaiian Ridge, near the Phoenix Islands, and bordering the North Atlantic. A principal aim of Leg 32 was to test correlations of these old anomalies by drilling specific sites on the Japanese and Hawaiian sets.2) Establish standard mid-Mesozoic to Recent paleontological-biostratigraphic reference sections for the (present-day) northwest Pacific. Shatsky Rise and Hess Rise are the northern-most of the few broad and irregularly shaped areas of the sea floor that are sufficiently shallow so calcareous fossils are likely to be preserved and yet are isolated from dilution by terrigenous components.3) Determine the paleolatitude for a specific period of volcanicity on Köko Guyot of the Emperor Seamount Chain, which, when compared with the paleolatitude of Midway Islands and the present-day latitude of the active volcanoes on Hawaii, can test a version of the hotspot theory-that a source of magma generation has remained fixed in the earth's mesosphere while the Pacific lithospheric plate has moved across it, with resultant volcanoes forming first the Emperor Seamounts and, after a change in direction of plate motion, the Hawaiian Ridge.Several other geological and operational goals were to include: tracing the paleoequator in the stratigraphic records at the deep-water and rise sites; gathering cores for isotope analysis for paleooceanography studies; det...