Mesozoic and Cainozoic rocks dredged from the South China Sea (Reed Bank area) and Sulu Sea and their significance for plate-tectonic reconstructions

Abstract

Outcrops of pre-Quaternary rocks were sampled by dredging and coring during two cruises of RV ‘Sonne’ in the South China Sea and Sulu Sea (1982, 1983). Late Triassic deltaic sandstones wih plant remains are the oldest sediments recovered. Late Jurassic/Early Cretaceous regional metamorphism is indicated by gneiss and garnet-mica schists exposed in the northwestern flanks of Reed Bank. These rocks, and occurrences of gabbro, diorite, dacite, rhyolite and siliceous shale prove that the Dangerous Grounds and Reed Bank are underlain by a continental fragment. During the period of seafloor spreading in the South China See a Late Oligocene to Early Miocene carbonate platform developed on this southwards-drifting continental fragment, which subsided in the Middle Miocene. Middle Miocene andesite and Early to Middle Miocene reefal carbonates were recovered from the Cagayan Ridge in the Sulu Sea. The new data are in accord with the plate-tectonic history developed by Taylor and Hayes (1980, 1983) and Holloway (1981).