Holocene Evolution of the Pearl River Delta: Mapping Integral Isobaths and Delta Progradation

Abstract

The Pearl River Delta (PRD, China) has undergone complex geological development within a multi-island faulted basin, shaped by the interplay of regional tectonic movements, Quaternary sea-level fluctuations, and fluvial-marine interactions. Despite a great number of studies on the Holocene sedimentary sequences and spatial differences of lithofacies and environments, scant attention has been paid to the overarching human influence on deltaic evolution and coastline modifications since the Neolithic epoch. To further elucidate the spatial variation in Holocene sedimentation and its underlying basement topography shaped during the Last Glacial Maximum (LGM), we compiled a comprehensive dataset incorporating borehole data from over 2800 cores (the maximum depth can reach 92.5 m) within the PRD. Subsequently, high-resolution isobath maps of Quaternary deltaic deposits were generated, offering unprecedented insights into sediment distribution. This dataset facilitated a nuanced reconstruction of pre-Holocene topography, revealing a zone characterized by elongated, deep-incised valleys governed by NW-SE fault orientations. Further, we delineated coastline shifts since the period of maximum Holocene transgression (~7000 years BP), contributing to an enhanced understanding of the formation and evolutionary patterns of the delta and river network oscillations. Our findings illuminate an increasing anthropogenic impact on the rate of fluvial sedimentation and land growth, particularly accentuated over the last two millennia, favoring deltaic accretion.

Human Impacts on Holocene Vegetation and Wetland Degradation in the Lower Pearl River, Southern China

“…A significant and important change in pollen spectra demonstrates that the flourishing Glyptostrobus marsh forest since about 5.1 ka BP was followed by a sharp degradation at cal. 2.5 ka BP, which coincides with rapid rice farming development in the region (Figure 7) and the acceleration of delta plain growth in the mouth of the Pearl River [35,40,41]. According to the AMS 14 C dating results of carbonized rice remains at Neolithic archaeological sites in Southern China, rice farming had spread southward by ~5 ka BP, followed by continued expansion into coastal areas of the South China Sea.…”

“…Deltaic sedimentary and microfossil data suggest that around 8-7 ka BP marked the highest stand of Holocene marine transgression, while mountains and hills directly bordered the paleoestuary coastline at the mouth of the Pearl River [14]. A number of studies propose that the upper delta areas had already experienced inundation by Holocene transgression along incised valleys as early as approximately 9 ka BP [11,34,35]. From approximately 4.3 to 2.5 ka BP, the local small basin underwent a transformation from an evergreen broad-leaved forest into a marsh coniferous forest, as evidenced by the abundant presence of Glyptostrobus pollen constituting 60-80% of the total pollen in zone III (Figures 3 and 5).…”

“…This mode of growth and distribution also makes them vulnerable to destruction in unusual landscape changes (such as soil erosion) caused by agricultural development. It was suggested that since the Qin and Han Dynasties, a large number of northern immigrants brought agricultural technology, associated with the rapid growth of the delta plain that led to an increase in land available for farming [14,35,47]. Since freshwater wetland provides good soil and land for rice cultivation, the Glyptostrobus forest has been extensively destroyed and converted into paddy fields.…”

Holocene environmental changes and prehistoric agricultural development along the coastal areas of South China to Southeast Asia

“…海岸带的总体趋势是一致的 [55] . 根据沿海地区的钻孔 沉积相研究结果, 闽江 [20] 、韩江 [32] 、珠江 [56,57] 、红 河 [58] 、湄公河 [59] 和湄南河 [60] 等河口/三角洲盆地虽然 目前大部分为平原的地区, 但在中全新世仍处于河口 或滨海沉积环境, 且暴露地表的平原土地面积十分有 限. 从时空分析的角度, 本研究根据高分辨的SRTM地 形数据, 结合钻孔沉积物的古环境分析结果, 展示出整 个亚洲东南部目前出露在地表上的大多数河口三角洲 图 6 华南地区不同海拔高度从低地(GY1)到丘陵山地(LTY、WDY和JXS)的孢粉记录对比 [29] .…”