INTRODUCTION

Ocean Drilling Program (ODP) Leg 202 was designed to study the timing, nature, and processes of late Cenozoic climatic and oceanographic changes in the southeast Pacific. During Leg 202, we recovered a total of 7081 m of sediment at 11 sites (Sites 1232–1241) in the southeast and equatorial Pacific, ranging in age from early Oligocene (~31.5 Ma) to Holocene (Figs. F1, F2, F3). At all sites, multiple holes were drilled to ensure continuous recovery of the stratigraphic section. At three sites (1238, 1239, and 1241), borehole logging operations produced data sets of remarkable quality, which allowed core-log integration. A complete description of Leg 202 recovered sediments and performed shipboard analyses is given in the Leg 202 Initial Reports volume (Mix, Tiedemann, Blum, et al., 2003). We successfully achieved the drilling goal of providing undisturbed and continuous sediment records along a latitudinal transect from 41S to 8N and an intermediate- to deepwater transect from 490 to 4070 m water depth that permit paleoceanographic studies on a variety of timescales, including centennial to millennial (102–103 yr), orbital (104–105 yr), and tectonic (>105 yr) time resolution.

These materials provide an excellent opportunity to test a broad set of hypothesis on

  1. The evolution of the South Pacific Ocean as it responds to and modulates the effects of major tectonic and climatic events, such as uplift of the Andes Mountains, closure of the CAS, and major expansion of polar ice sheets;
  2. The linkage between climate and biogeochemical changes in the high latitudes and the equatorial Pacific, related to rhythmic changes in Earth's orbit, and the relationship of such changes to well-known glacial events of the Northern Hemisphere; and
  3. The timing of global and regional changes in climate, biota, and ocean chemistry on scales of centuries to millennia.

Four years of postcruise work have yielded substantial progress. Here we present a summary of Leg 202 state-of-the-art science by (1) providing an overview of the papers that contributed to this Scientific Results volume and (2) synthesizing the reports both in the volume and in the external literature, and (3) evaluating the current state of progress toward meeting the overall leg objectives, recognizing that ongoing and future efforts will continue to capitalize on these extraordinary materials and add to these results over the coming decades.

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