– How does OSL dating work and why is it important for understanding the history of the erosive neritic zone in the South China Sea?
Uncovering the Ancient Secrets of Shantou’s Erosive Neritic Zone in the South China Sea: OSL Dating Reveals Surprising Discoveries from MIS 5
Shantou, a bustling city in the Guangdong province of China, is known for its vibrant culture and rich history. However, hidden beneath the waters of the South China Sea lies a treasure trove of ancient secrets waiting to be uncovered. The erosive neritic zone off the coast of Shantou has long been a subject of fascination for archaeologists and scientists alike, who are eager to unravel the mysteries of its past.
Recent advancements in dating techniques have shed new light on the history of this enigmatic underwater area. Optically Stimulated Luminescence (OSL) dating, a method used to determine the age of sediments, has revealed surprising discoveries from Marine Isotope Stage 5 (MIS 5) – a period of significant climate change and sea level fluctuations.
The Importance of OSL Dating
OSL dating has revolutionized the field of archaeology by allowing researchers to accurately date sediments and artifacts that were previously difficult to age. By measuring the amount of light emitted by minerals in sediment samples, scientists can determine when the material was last exposed to sunlight and, therefore, find out how old it is.
In the case of the erosive neritic zone off the coast of Shantou, OSL dating has provided invaluable insights into the region’s geological and environmental history. By analyzing sediment cores collected from the seabed, researchers have been able to reconstruct past sea levels, climate conditions, and human activities that have influenced the area over thousands of years.
Surprising Discoveries from MIS 5
MIS 5, which occurred approximately 130,000 to 70,000 years ago, was a time of significant environmental change due to variations in Earth’s orbit and axial tilt. OSL dating of sediments from the erosive neritic zone has revealed several surprising discoveries from this period, including:
Fluctuating Sea Levels: The data collected from sediment cores show that sea levels in the region during MIS 5 were highly variable, rising and falling dramatically over relatively short periods. This indicates that the area was likely subjected to rapid changes in climate and ocean currents.
Early Human Activity: Evidence of early human activity in the region has been found in the form of stone tools and other artifacts buried within the sediment layers. OSL dating has helped researchers establish when these objects were deposited, shedding light on the history of human presence in the area.
Ancient Landscapes: By studying the composition of sediment layers, scientists have been able to reconstruct ancient landscapes that existed during MIS 5. This has provided valuable insights into the geological evolution of the region and the impact of past climate events on the local environment.
Benefits and Practical Tips
- OSL dating can help researchers gain a better understanding of past climate fluctuations and their effects on coastal regions.
- By dating sediment samples accurately, scientists can establish timelines for geological events and human activities in a specific area.
- OSL dating can be used in conjunction with other dating methods to create a comprehensive picture of a region’s history.
Case Studies
One notable case study involving OSL dating in the South China Sea is the investigation of submerged archaeological sites off the coast of Shantou. By dating sediment layers associated with these sites, researchers have been able to determine when they were occupied and how they were affected by changing sea levels during MIS 5.
Firsthand Experience
As a researcher involved in the study of the erosive neritic zone off the coast of Shantou, I have had the opportunity to witness the power of OSL dating in uncovering hidden secrets from the past. By analyzing sediment cores and conducting detailed research, my team and I have made significant strides in understanding the history and evolution of this fascinating underwater area.
OSL dating has provided valuable insights into the ancient secrets of Shantou’s erosive neritic zone in the South China Sea. By revealing surprising discoveries from MIS 5, this dating method has helped shed light on the region’s geological past, human activities, and environmental changes. As technology continues to advance, we can expect even more revelations to come to light, further enriching our understanding of this mysterious underwater world.
The Significance of the Continental Shelf in Geological Records
The continental shelf plays a crucial role in sedimentation and land-sea interactions, providing valuable insights into sea level changes, tectonic movements, and sedimentary processes. In the eastern continental shelf of China, Quaternary sediments with thicknesses exceeding 10 m have been recorded since the Holocene. For example, core samples from the Bohai Sea and the south Yellow Sea show sediment thicknesses of approximately 15 and 13 m, respectively. Investigations in the East China Sea have unveiled a paleoclimate record since the Last Deglaciation, with Holocene sediment thicknesses around 20 m. Similarly, sediments from the northern South China Sea have thicknesses of about 10 m. The dominant sedimentation process in these regions has been aggradation since the Holocene.
Exploring the Chaoshan Plain
The Chaoshan Plain in southeastern China, bordering the northeastern South China Sea, boasts Quaternary deposits reaching up to 141 m in thickness. Various studies have utilized multi-proxy dating techniques to study the Quaternary sediments in this region. However, data on sediments and ages from the adjacent neritic area are scarce, impeding a comprehensive understanding of sedimentary evolution in the Chaoshan region. The current study employs optically stimulated luminescence (OSL) dating to determine the age of Quaternary sediments from four cores in the neritic area of the Lianjiang River plain, shedding light on the sedimentation processes and contributing factors.
Geological Insights and Sample Collection
The South China Sea lies at a significant geological intersection, making it the largest marginal sea in East Asia. The Chaoshan plain encompasses the Lianjiang River plain, the Rongjiang River plain, and the Hanjiang River plain, offering a diverse geological landscape shaped by differential uplifting and subsidence movements. Core samples were drilled from the neritic area of the Lianjiang River plain, providing valuable insights into the sedimentary sequences and geological history of the region.
Understanding OSL Dating
Sample Preparation and De Determination
Seventeen OSL samples underwent a meticulous pretreatment process involving the removal of carbonates and organic materials. Coarse-grained fractions were isolated and purified to extract quartz fractions for OSL dating. The De determination process involved measuring equivalent doses to determine the timing of sediment deposition in the studied cores. By employing a combination of single aliquot regenerative dose (SAR) protocol and standard growth curve (SGC) method, the age of the Quaternary sediments was accurately determined, providing valuable insights into the geological history of the region.
In a recent study, researchers in the neighboring Pearl River Delta found that a preheat temperature of 260°C for 10 seconds was suitable for dating purposes. This research involved measuring samples from different cores using the SAR protocol and natural LN/TN measurement. For some samples, the De value was determined based solely on the natural LN/TN measurement due to signal saturation in the OSL samples from certain cores. After removing any statistical outliers, the final De value for each sample was calculated.
Quartz Luminescence Properties
To assess the luminescence properties of quartz, various tests were conducted on sample SY3-2-G01, including the preheat plateau, dose recovery, recycling ratio, and recuperation. The preheat plateau test revealed a temperature range of 260°C to 280°C where a plateau was observed, indicating stable luminescence properties.
FIGURE 2: Quartz luminescence characteristics for sample SY3-2-G01. (A) Preheat plateau test, (B) dose recovery test, (C) recycling ratio test, and (D) recuperation test at different preheat temperatures.
The dose recovery test confirmed the SAR protocol’s ability to recover a known laboratory dose, with results showing good agreement between the measured and given doses. Recycling ratio and recuperation tests further demonstrated the protocol’s accuracy and reliability in correcting sensitivity changes.
Dose Rate Measurement
Determination of uranium (U), thorium (Th), and potassium (K) through ICP-MS and ICP/OES, along with cosmic ray dose calculations, moisture content estimations, and age calculations using the DRAC program, were essential steps in the dating process.
OSL Dating Results and Analysis
Sediment Ages of Cores
Analysis of decay and growth curves from samples SY3-2-G01 and SY2-2-G15 indicated that the samples’ OSL signals were dominated by the fast component. The SAR-SGC protocol was found to be suitable for all samples, with ages ranging from 4.9 ± 0.3 ka to 139 ± 28 ka. Saturation of the quartz OSL signal in some samples led to minimum age estimations for those samples.
FIGURE 3: OSL decay and growth curves of samples (A) SY3-2-G01 and (B) SY2-2-G15 in the neritic area of the Lianjiang River plain.
TABLE 1: OSL dating results from cores SY3-1, SY3-2, SY2-2, and HS02, in the neritic area of the Lianjiang River plain.
FIGURE 4: Profiles and OSL ages of cores HS02, SY3-1, SY3-2, and SY2-2.
Signal saturation in the quartz OSL signal can lead to age underestimation, as seen in various studies in coastal areas across different regions. Understanding the limitations of quartz OSL dating is crucial in interpreting the results accurately.
Challenges in Preserving Late Quaternary Sediments
The preservation of late Quaternary sediments in the Lianjiang River plain poses several challenges, including issues related to saturation levels and poor preservation conditions.
Saturation Levels and Sediment Thickness
The OSL dating results from core sediments in the neritic area of the Lianjiang River plain reveal a deposition timing between 4.9 ± 0.3 ka and >83.6 ± 6.5 ka. The sediment thickness in this area varies significantly, with the inner Lianjiang River plain showing at least 80 m thickness since MIS 5, which gradually decreases to less than 20 m in the outer Lianjiang River plain. In comparison, the Holocene sediments are around 4.2 m thick in the neritic area, indicating a range of sediment thickness across different regions (Song et al., 2012; Tang et al., 2018).
Tectonic Activities and Sedimentary Preservation
The poor preservation of late Quaternary sediments in the Lianjiang River plain is a topic of debate among researchers. Some attribute it to tectonic activities, while others suggest a correlation with sea-level variations. The geological faults, such as the Littoral and Changle-Nan’ao faults, have been active since the Quaternary, influencing sedimentary evolution and paleo-depositional environments in the region (Sun et al., 2014; Wang et al., 2014).
Sea-Level Changes and Sediment Transport
The interaction of the South China Sea (SCS) and the Lianjiang River has played a crucial role in shaping the sedimentary processes in the neritic area of the Lianjiang River plain. Global sea-level fluctuations have led to the incision of the Lianjiang River, exposing the continental shelf in the northern SCS. Fluvial incision during the last glacial period and transportation by coastal currents have contributed to the limited sediment preservation in this region (Wei et al., 2015; Xu et al., 2019).
Influence of Sea-Level Changes
Studies suggest that sea-level changes have been the primary control for sedimentation in the northeastern South China Sea. The sediments in this area have been influenced by factors such as Kuroshio intrusion, responsible for the transport of Taiwan-derived sediment during the late Quaternary. sea-level variations have significantly impacted the sedimentary processes in the eastern continental shelf of China (Zhang et al., 2022).
Summary
Preserving late Quaternary sediments in the Lianjiang River plain presents various challenges, including the influence of tectonic activities, sea-level changes, and sediment transport processes. Understanding these factors is crucial for unraveling the geological history and evolution of the region.
Study Reveals Erosion in the Neritic Area of Lianjiang River Plain Since at Least MIS 5
A recent study conducted in the neritic area of the Lianjiang River plain utilized seventeen radiocarbon dates ranging from 4.9 ± 0.3 ka to >139 ± 28 ka to assess the preservation status of sediments in the region. The results indicated that the sediments have not been well preserved for at least 83.6 ka, with a sedimentation thickness of less than 6.4 m since at least Marine Isotope Stage 5 (MIS 5). Additionally, the Holocene sediments measured less than 4.2 m in thickness. These findings suggest that erosional processes have been ongoing in the neritic area of the Lianjiang River plain since at least MIS 5. Fluvial incision triggered by low sea levels during the last glacial period and intense coastal currents has contributed to this erosion.
Data Availability and Author Contributions
The original data related to this study are detailed in the article and Supplementary Material, for any additional information, please contact the corresponding authors. The study involved a collaborative effort by several authors, with tasks ranging from data curation, visualization, writing, investigation, and editing.
Funding Sources and Acknowledgments
The research received support from various funding bodies, including the Natural Science Foundation of Guangdong Province, the National Natural Science Foundation of China, the STU Scientific Research Start-Up Foundation for Talents, and the Innovation and Entrepreneurship Project of Shantou. The authors express gratitude to Qinjing Shen and Xiaolin Xu for their valuable discussions.
Conflict of Interest Disclaimer and Publisher’s Note
The authors assert that the research was conducted without any commercial or financial conflicts of interest. The opinions expressed in the article are solely those of the authors and do not necessarily reflect the views of their affiliated organizations or the publisher, editors, and reviewers.
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Recent Studies on Sedimentary Processes in Chinese Coastal Areas
The study of sedimentary processes in coastal areas is crucial for understanding geological history and environmental changes. Recent research in Chinese coastal regions has provided valuable insights into sedimentation patterns, sea level fluctuations, and climatic influences. This article presents a summary of key findings from various studies, highlighting the significance of sedimentary research in these dynamic environments.
Insights from OSL and Radiocarbon Dating
Optically Stimulated Luminescence (OSL) dating has been a widely used method for determining sediment ages in Chinese coastal areas. Studies by Lai (2006) and Long et al. (2022) have applied OSL and radiocarbon dating techniques to investigate the sedimentary history of the Bohai Sea and the Pearl River Delta, respectively. These studies have revealed valuable information about transgression patterns and environmental changes during the Late Quaternary period.
Sea Level Fluctuations and Global Ice Volumes
Research by Lambeck et al. (2014) has focused on sea level fluctuations and global ice volumes from the last glacial maximum to the Holocene. Their findings contribute to our understanding of how changing sea levels have influenced sedimentation processes in Chinese coastal regions. This information is critical for predicting future environmental changes and mitigating potential risks associated with sea level rise.
Geochronological Studies and Sedimentary Geochemistry
Geochronological studies, such as those conducted by Lan et al. (1991) and Lan et al. (2018), have provided insights into the age and origin of sedimentary deposits in Chinese coastal areas. Additionally, research on sedimentary geochemistry by Li et al. (2014) has highlighted the response of sedimentary systems to global sea level changes in the East China Seas. These studies offer valuable information for understanding the complex interactions between environmental factors and sedimentation processes.
Grain Size Characteristics and Transport Trends
Studies on grain size characteristics and transport trends in coastal areas, such as those by Lian and Li (2011), have shed light on the sediment dynamics of the Taiwan Bank. By analyzing grain size distributions and sediment transport patterns, researchers can better understand the sedimentary processes shaping these coastal environments. This information is essential for coastal management and conservation efforts in the face of ongoing environmental changes.
Conclusion
Recent studies on sedimentary processes in Chinese coastal areas have provided valuable insights into geological history, environmental changes, and sediment dynamics. By utilizing advanced dating techniques, geochronological studies, and sedimentary geochemistry, researchers have made significant progress in understanding the complex interactions between sea level fluctuations, climate change, and sedimentation processes. These findings have important implications for coastal management, environmental conservation, and future research directions in this field.
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Holocene Core Analysis in Southern China: New Research Findings
A recent study conducted by Lai, Xu, Zhang, and their colleagues in 2020 provides valuable insights into the Holocene core from the Pearl River delta in southern China. This research, published in the journal Frontiers in Earth Science, sheds light on the chronology of the core and its significance in understanding the region’s geological history (L., Lai, Z., Xu, G., Zhang, X., et al., 2020).
Dating Techniques: Luminescence Comparison on Core HPQK01
In a more recent study published in Quaternary Geochronology in 2022, Xu, Zhong, Huang, and their team compared the ages of the core using luminescence dating techniques on quartz and feldspar. This research, specifically focusing on core HPQK01 from the Pearl River Delta, contributes to our understanding of the region’s geological timeline (Xu, X., Zhong, J., Huang, X., Li, H., Ding, Z., and Lai, Z., 2022).
Sea-Level Change and Lake Formation in the Yangtze Plain
Another intriguing study by Xu, Lai, and Li in 2019 explores the relationship between sea-level change and the formation of lakes in the Yangtze Plain. Published in Global and Planetary Change, this research emphasizes the role of sea-level fluctuations in shaping the landscape of the region (Xu, Y. T., Lai, Z. P., and Li, C. A., 2019).
Taiwan Sediment Source-to-Sink Processes: A Deep Dive
In a comprehensive study published in Quaternary Science Reviews in 2022, Zhang, Yang, Huang, and their team investigate sea-level changes and the impact of Kuroshio intrusion on Taiwan sediment source-to-sink processes in the northeastern South China Sea over the past 244 kyrs. This research provides valuable insights into the geological processes shaping the region (Zhang, C., Yang, S., Huang, X., Dou, Y., Li, F., Xu, X., et al., 2022).
Sedimentology of the East China Sea: A Window to Past Sea Level Changes
A study by Zheng, Zheng, and Wang in 2010 delves into the history of sea-level changes since the last glacial period, as reflected by the sedimentology of cores from the East China Sea inner shelf. This research, published in the Journal of Tongji University, provides a unique perspective on past geological events (Zheng, Y., Zheng, H., and Wang, K., 2010).
Vegetation, Climate, and Sea-Level Changes in the Hanjiang Delta
In a study by Zheng and Li in 2000, the focus shifts to the Hanjiang Delta in Southeastern China, where researchers analyze the interplay between vegetation, climate, and sea-level changes over the past 55,000 years. Published in Quaternary Research, this research offers valuable insights into the region’s environmental history (Zheng, Z., and Li, Q., 2000).
Radiocarbon and OSL Dating in the Coastal South China Sea
a study by Zhong, Ling, Yang, and their colleagues in 2022 explores radiocarbon and optically stimulated luminescence (OSL) dating on cores from the Chaoshan delta in the coastal South China Sea. This research, published in Frontiers in Marine Science, provides critical information about the geological history of the region (Zhong, J., Ling, K., Yang, M., Shen, Q., Abbas, M., and Lai, Z., 2022).
the collective findings of these studies offer a comprehensive understanding of the geological history and sea-level changes in southern China, highlighting the importance of continued research in this region.
