Holocene delta evolution and sequence stratigraphy of the Pearl River Delta in South China

Abstract

We analyzed the sedimentary characteristics and chronostratigraphy of the Pearl River Delta in South China, and discussed the Holocene stratigraphic characteristics and the filling process since the Holocene, based on 90 boreholes. Our results showed that the maximum transgressive surface of the Pearl River Delta was located in the soft marine silt horizons, whereas it was shown as an erosion surface in areas with tidal scour. From bottom to top, Holocene sedimentary sequences were fluvial facies, floodplain-estuary facies, and estuary-delta facies in the paleo-valley, while the paleo-interfluve sequences were described as littoral facies, estuary facies, and delta facies. Vertical accumulation sequences of Holocene sediments were shown primarily as positive tapering-shaped sequences with no typical foreset, topset, or other sedimentary sequences of the Gilbert Delta. The paleo-Pearl River estuary had different evolution models in the highstand systems tract (HST) compared with other large deltas worldwide, in that it is dominated by a unique and complex geomorphologic boundary, and that it is a multi-sourced delta compounded by the independent and parallel development of fluvial sedimentary bodies with different scales. A huge estuary was formed in the present Pearl River Delta area when the post-glacial transgression reached maximum at about 6 ka BP. The estuary was divided into two parts by obstruction of a series of islands, an upper part composed of the semi-enclosed inner paleo-bay connected to rivers and a lower part consisting of the outer paleo-bay connected to the ocean. Both of these areas were interlinked by only a few narrows, in which the fluvial sediments are accumulated primarily in the inner paleo-bay. During 6-2 ka BP, the sedimentation in various regions of the inner paleo-bay occurred simultaneously with independent development under the remodeling and transformation effect of complex boundaries on river and ocean dynamics. After 2 ka BP, the evolution of the delta is no longer a simple natural process, but rather a common remodeling process accomplished by nature and humans.Pearl River Delta, Holocene, stratigraphic framework, delta evolution Citation:Wei X, Wu C Y. Holocene delta evolution and sequence stratigraphy of the Pearl Deltas consist of large bodies of estuary sediments that are accumulated as a result of dramatic variations in sedimentary dynamic conditions when a river flows into a lake or ocean. The primary conditions dominating the development and evolution of a delta include climate and regional tectonics, as well as the dynamic equilibrium between rivers and lakes/oceans, relative sea-level fluctuations, sediment supply rate, and topography of the receiving basin. Due to variations in these factors and their interactions, the evolutionary process of a delta is complex. Early studies of the Mississippi Delta are now considered classic [1-3], therefore, this delta has long been taken as the model for deltas worldwide. However, Van Andel and Curray [4] found that

Evolution status of the distal mud deposit associated with the Pearl River, northern South China Sea continental shelf

“…This rate fits in well with the rates of 0.8-1.0 mm yr À1 during 7.84-3.95 kyr BP (Owen et al, 1998). Similarly, Wei and Wu (2011) showed that the average accumulation rate for the Holocene was 1.3 mm yr À1 at the time of 10.0-7.5 kyr BP, 2.3 mm yr À1 for the period of 7.5-5.0 kyr BP, 1.9 mm yr À1 between 5.0 and 2.5 kyr BP, and 2.3 mm yr À1 thereafter over the entire Pearl delta. Huang et al (1983) obtained slightly different rates, i.e., 2.7 mm yr À1 during 7.5-5.0 kyr BP, 2.2 mm yr À1 for the period of 5.0-2.5 kyr BP, and 2.2 mm yr À1 thereafter.…”

Continental slope-confined canyons in the Pearl River Mouth Basin in the South China Sea dominated by erosion, 2004–2018

“…At the river mouth, the Pearl River delta has prograded at an average rate of 17 m/yr over the past 6,000 years (Huang and Song, 1981;Fyfe et al, 1999). The present Pearl River delta is confined within the estuary of the river (Wei and Wu, 2011;Wu et al, 2014).…”

Architecture, evolution history and controlling factors of the Baiyun submarine canyon system from the middle Miocene to Quaternary in the Pearl River Mouth Basin, northern South China Sea

“…3A and C). Nowadays, the Pearl River delta is confined in the estuary of the Pearl River (Wei and Wu, 2011), and the outer shelf is covered with sand waves (Wang, 2000;Zhuo et al, 2014).…”