This synthesis summarizes results presented in more than 35 papers published not only in this Leg 185 Scientific Results volume but also in several journal articles (Table T1) and, specifically, in a special thematic series of articles on Oceanic Inputs to the Subduction Factory published in Geochemistry, Geophysics, and Geosystems (G3) (Table T2). Leg 185 science also supported the theses of 12 students in universities around the world (Table T3).
Drilling at Sites 801 and 1149 during Ocean Drilling Program (ODP) Leg 185 (Plank, Ludden, Escutia, et al., 2000) has resulted in dating of the oldest basement and sediments in the western Pacific. Penetration into old Pacific crust has helped scientists solve some fundamental problems, such as the nature of the Earth's magnetic field during the Jurassic "quiet" period and the temperature of the Pacific mantle prior to the arrival of the Cretaceous superplume.
As much of the oldest seafloor on Earth is close to subduction zones, the principal aim of Leg 185 was to quantify the geochemical composition of the basement and sedimentary sections being subducted at the Izu-Bonin-Mariana Trench. This effort is part of the U.S. National Science Foundation (NSF) MARGINS and Geochemical Earth Reference Model (GERM) initiatives.
This paper is divided into four sections. The first deals with the history of drilling into Jurassic basement in Hole 801C, our current knowledge of this basement, and new perspectives that Leg 185 has opened on the world's oldest oceanic crust. The second section deals with the sedimentary history of the western Pacific, based in large part on the reference site drilled at Site 1149. In particular, this information helps define the quantity and types of sediments that are being subducted into the west Pacific arcs. The latter is particularly important for the third section of this paper, which deals with the bulk geochemistry of basement and sediments as input to subduction zones and how this material is recycled through the solid Earth. The final section outlines the role Leg 185 played in developing new protocols to study microbial life in deep ocean sediments and crust.