Clinoform growth and sediment flux into late Cenozoic Qiongdongnan shelf margin, South China Sea

Abstract

The South China Sea continental margin in the Qiongdongnan Basin (QDNB) area has incrementally prograded since 10.5 Ma generating a margin sediment prism more than 4km‐thick and 150–200 km wide above the well‐dated T40 stratigraphic surface. Core and well log data, as well as clinoform morphology and growth patterns along 28 2D seismic reflection lines, illustrate the evolving architecture and margin morphology; through five main seismic‐stratigraphic surfaces (T40, T30, T27, T20 and T0) frame 15 clinothems in the southwest that reduce over some 200 km to 8 clinoforms in the northeast. The overall margin geometry shows a remarkable change from sigmoidal, strongly progradational and aggradational in the west to weakly progradational in the east. Vertical sediment accumulation rate increased significantly across the entire margin after 2.4 Ma, with a marked increase in mud content in the succession. Furthermore, an estimate of sediment flux across successive clinoforms on each of the three selected seismic cross sections indicate an overall decrease in sediment discharge west to east, away from the Red River depocenter, as well as a decrease in the percentage of total discharge crossing the shelf break in this same direction. The QDNB Late Cenozoic continental margin growth, with its overall increased sediment flux, responded to the climate‐induced, gradual cooling and falling global sea level during this icehouse period.

Spatial and temporal variability of sediment infilling and episodic rifting in the North Pearl River Mouth Basin, South China Sea

“…Because the fluvial-deltaic system is dominant in the PRMB during the rifting stage (Wu et al, 2016), the relative height is determined by the thickness of the clinoform (Chen et al, 2019; and the rifting rate, as shown in Equation 1. Then, based on the fluvial-deltaic model (Hampson et al, 2014), the sediment migration distance is u(x).…”

Clinoforms and clinothems: Fundamental elements of basin infill

“…Amorosi et al, 2019;Plink-Bjorklund, 2019) to shelf-edge scale (e.g. Bryn et al, 2019;Gamberi et al, 2019;Gan, Steel, Olariu, & Almeida Jr, 2019;Olariu et al, 2019;Patruno et al, 2019;Steel et al, 2019) and continental-margin scale (Chen, Steel, Wang, Zhao, & Olariu, 2019;Midtkandal et al, 2019). Continuous and repeated erosion is commonplace in the topset areas, F I G U R E 3 Conceptual section of nested clinoforms as the result of incremental margin growth: as in Matryoshka dolls, progressively smaller-scale clinoforms and clinothems 'appear' as we gradually zoom into a continental margin succession.…”

“…The study highlights challenges associated with exploration for sandstone reservoirs in seismic wedges in an outer shelf setting. Chen et al, 2019, integrate sediment cores, well-log and 2D seismic data to analyse a >4-km-thick continental-margin sediment wedge of stacked transgressive-regressive successions, and to estimate the sediment discharge into the Late Cenozoic Qiongdongnan Basin, South China Sea. Their contribution quantifies the along-strike, strongly decreasing sediment flux on clinothems, on both flanks of the supply fairway (likely Red River supply), during the building of the accreting margin.…”

“…Amorosi et al, 2019; Plink‐Bjorklund, 2019) to shelf‐edge scale (e.g. Bryn et al, 2019; Gamberi et al, 2019; Gan, Steel, Olariu, & Almeida Jr, 2019; Olariu et al, 2019; Patruno et al, 2019; Steel et al, 2019) and continental‐margin scale (Chen, Steel, Wang, Zhao, & Olariu, 2019; Midtkandal et al, 2019). Continuous and repeated erosion is commonplace in the topset areas, as highlighted by frequent downcutting of fluvial and delta‐distributary channels (Gan et al, 2019) and by shelf‐edge incisions (Olariu et al, 2019).…”

“…Thick successions showing vertically stacked progradation–transgression units or an overall tendency to stack units from a progradation to aggradation style (as judged from the shelf‐break trajectory). These are the building blocks of many topsets and can be distinguished despite the otherwise tramline‐like seismic reflections of the shelfal parts of the topsets, particularly in their mid‐to‐outer reaches, where water depth can be greater and subsidence rate higher (Chen et al, 2019; Gamberi et al, 2019; Magyar et al, 2019; Steel et al, 2019; Zhang et al, 2019). In delta‐scale clinoforms, these cycles are commonly less easy to identify because of the ephemeral nature of elemental features constituting the clinoforms themselves (Trincardi et al, 2019), and because of the necessity of multidisciplinary approach in identifying key stratigraphic clinothem‐bounding surfaces (Amorosi et al, 2019; Playter et al, 2018).…”