Abstract
Establishing a reliable chronological framework for sediments is crucial to the reconstruction of evolution process of estuarine delta, and the study of regional paleoenvironmental history, e.g. sea level fluctuations due to global climatic changes. High resolution chronology is still very limited for Holocene sediments in the Pearl River delta (PRD) in southern China. This study tries to construct a detailed chronology for core DA of 37.7 m in depth by using luminescence (seven samples) and radiocarbon (fourteen samples) dating techniques. Our results indicate that both luminescence and radiocarbon dating methods are suitable for the Holocene sediments in the PRD and that sediments of core DA were deposited during 7.3-0.18 ka. The 14C age is generally older than the OSL age for the sediment at the similar depths, and the age difference increased from 0.45 ka at the depth of 21 m to 0.98 ka at the depth of 35 m. The reason that 14C ages are relatively older might be caused by the carbon-reservoir effect which requires further study. The sedimentation rate increased from 3.74 m/ka during 7.3-2 ka to 7.92 m/ka in the last 2 ka. The appearances of rusty stains in upper unit of the core revealed that the water level was gradually falling. After the formation of underwater sand body at about 2 ka, the sediment was subject to continuous shifting between submergence and exposure.
Highlights
Ten 14C ages of core PRD11 in the central Pearl River delta (PRD) showed that the regional Holocene stratum was formed during 8.6 to 0.4 cal ka BP, and that the sedimentation rate decreased from 1.74 m/ka (8.6 to 4.7 cal ka BP) to 0.72 m/ka (4.7–0.4 cal ka BP) (Liu et al, 2016)
By radiocarbon dating on core HKUV11 from a near-shore location of the northern South China Sea, seven marine shell ages revealed that the stratum above the hard and mottled sandy-clayey silt was formed during 9.2–1.6 cal ka BP, with a stable sedimentation rate of 1.8 m/ka (Wu et al, 2017)
Our results indicate that both luminescence and radiocarbon methods are applicable for dating the Holocene sediments in the PRD
Summary
As the product of complex dynamic actions in littoral zones, estuarine delta is a key area in studying the regional paleoenvironmental history, and provides an important window to understand the coupling interplay among eustasy, climate, and tectonics on the deltaic evolution (e.g., Hori et al, 2001; Saito et al, 2001; Sarkar et al, 2009; Tang et al, 2010; He et al, 2017; Pennington et al, 2017; Li et al, 2018; Bomer et al, 2019; Pleuger et al, 2019; Xu et al, 2019). Hu et al (2013) obtained ten AMS 14C ages, ranging from 8.0 to 1.2 cal ka BP, on mollusk fossils for a 6 m-thick mud layer with occasional shell-rich intervals from core B2/1, which was located in the mouth of the Pearl River Bay. Ten 14C ages of core PRD11 in the central PRD showed that the regional Holocene stratum was formed during 8.6 to 0.4 cal ka BP, and that the sedimentation rate decreased from 1.74 m/ka (8.6 to 4.7 cal ka BP) to 0.72 m/ka (4.7–0.4 cal ka BP) (Liu et al, 2016). By radiocarbon dating on core HKUV11 from a near-shore location of the northern South China Sea, seven marine shell ages revealed that the stratum above the hard and mottled sandy-clayey silt was formed during 9.2–1.6 cal ka BP, with a stable sedimentation rate of 1.8 m/ka (Wu et al, 2017)
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