Site U1435: Expedition 349

Abstract

Coring at Site U1435 became a high priority after failing to achieve our basement objectives at Site U1432. Site U1435 is located on a structural high at the transition between the extended continental crust and the oceanic crust. Similar conspicuous structural-high features can be found on the continent/ocean boundary in many other seismic profiles crossing the South China Sea northern margin and therefore appear to represent tectonic structures typical of the area. The true lithology and formation mechanism of this structural high were speculative; it could be a volcanic extrusion associated with continental extension at the onset of seafloor spreading, lower crust material emplaced from preferential lower crust extension, exhumed mantle material, or a structural high composed of older (Mesozoic) sedimentary rocks. Coring at this location was designed to help pinpoint the exact nature of this structure and improve our understanding of early continental breakup, the rift-to-drift transition, and seafloor spreading processes.