Recurrent slope failure enhancing source rock burial depth and seal unit competence in the Pearl River Mouth Basin, offshore South China Sea

Abstract

High-quality 3-D seismic data are used to assess the significance of mass-transport deposits (MTDs) to the evolution of the Pearl River Mouth Basin (South China Sea). Basal shear surfaces and lateral margins of seven recurrent MTDs are mapped to reveal a general NE-SW transport direction throughout the Late MioceneQuaternary. A key result of our analysis is the perceived relationship between the recurrence of slope instability in the study area and the Dongsha Tectonic Event. Using borehole data to constrain the ages of interpreted MTDs, we show that tectonic uplift in the northern South China Sea led to slope oversteepening in the Late Miocene (between 10.5 Ma and 5.5 Ma), preconditioning it to fail recurrently for more than10 Ma. Interpreted MTDs are shown to enhance burial depths of source and reservoir units, and improve seal competence in lower-slope areas. Conversely, upper slope regions record important erosion and reduced sealing capacity in Late Cenozoic strata. As a result, we postulate that the thickness variations imposed by MTDs on Late Miocene-Quaternary strata have important implications to petroleum plays in the South China Sea.

Along-strike segmentation of the South China Sea margin imposed by inherited pre-rift basement structures

“…They are interpreted as recurrent mass-wasting deposits accumulated along faulted crustal blocks (e.g. Zhao et al, 2015). During the deposition of Unit 2A, the shelf break was located on the structural high between the Baiyun and Liwan Sags (Fig.…”

“…8b). Recurrent mass-transport deposits, imaged as highly discontinuous to chaotic strata over laterally continuous seismic reflections, are identified on the continental slope off the Dongsha Islands (see also Zhao et. al., 2015).…”

Morphology, age and sediment dynamics of the upper headwall of the Sahara Slide Complex, Northwest Africa: Evidence for a large Late Holocene failure

“…Hence, the recognition of submarine landslides on continental margins is important to: a) the recognition of areas prone to slope instability on modern continental slopes, b) the investigation of possible triggers of slope instability, and c) the investigation of the global causes of submarine landsliding such as eustasy, tectonics, and climatic events (Vanneste et al, 2014). Other factors that have been proposed to trigger submarine landslides at a local scale include high sedimentation rates (Leynaud et al, 2007;Li et al, 2014), excess pore pressure (Berndt et al, 2012), gas hydrate dissociation (Sultan et al, 2004) and earthquakes (Sultan et al, 2004;Zhao et al, 2015).…”

Widespread hydrothermal vents and associated volcanism record prolonged Cenozoic magmatism in the South China Sea

“…In addition, regional uplift, fault reactivation, erosion and accelerated depositional rates after the final stages of continental breakup, are attributed to magmatic activity taking place in the region of interest to this study (Lüdmann and Wong, 1999;Carter et al, 2000;Fyhn et al, 2009;Savva et al, 2013;Zhao et al, 2015;Fan et al, 2019).…”

“…The effective duration of plume activity should correspond to a relatively long interval of time, and can explain the distribution and timing of magmatism and hydrothermal seepage in the South China Sea. Thermal weakening of the lithosphere by the hot mantle also promoted regional uplift, fault reactivation, erosion and accelerated depositional rates around the northern South China Sea (Lüdmann and Wong, 1999;Carter et al, 2000;Fyhn et al, 2009;Savva et al, 2013;Zhao et al, 2015;Zhao et al, 2016;Fan et al, 2019).…”