Tectonic-stratigraphic division and blind fold structures in Nansha Waters, South China Sea

Extensive multiple-channel reflection seismic data have been collected in the Nansha (Spratley Islands) Waters. the southern margin of the South China Sea. Stratigraphic correlation is shown with focus on a comprehensive geophysiXcal survey line run front offshore NW Sabah to offshore SE Vietnam. According to the varying tectono-stratigraphy from southeast to northwest, five tectonic belts can be determined i.e. the Palawan-Borneo Nappe, Nansha Trough. Nanwei-Liyue Compressive Belt, Zheng'he Extensional Belt and the Circum-Southwest Subbasin Belt. In the Palawan-Borneo Nappe. Neogene-Quaternary deposits were highly upthrust northwestwards, resulting in a series of moderately to tightly folded anticlines separated by open synclines. The Nansha Trough was a narrow. deep-water belt filled with thick. undisturbed Neogene-Quaternary deposits. The Nanwei-Liyue Compressive Bell was dominated by strongly folded paleo-anticlines: overlain by an undeformed sedimentary cap with a pronounced hiatus of Paleogene sediments. The Zheng'he Extensional Belt consisted of a rugged topography and Paleogene half-grabens bounded by listic faults. The major extensional faults were reactivated to cut through the overlying Neogene-Quaternary deposits. Over the Circum-Southwest Subbasin Belt. Neogene-Quaternary deposits draped on the largely subsided, fault blocks related to the Late Oligocene-Mid-Miocene seafloor spreading. Based on the regional stratigraphic correlation, the prominent paleo-anticlines found within the Nanwei-Liyue Compressive Belt are deduced to consist of mainly Mesozoic marine sediments that were compressed in the Late Mesozoic Era. Therefore, the Nansha Microcontinent Block is shown to be a collision complex assembled during Late Mesozoic Era. (C) 2004 Elsevier Ltd. All rights reserved.