Astronomical time scale and Paleo-water depth evolution of the Miocene in the Pearl River Mouth Basin

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2025-03, Vol.661, p.112736, Article 112736
• Main Authors: Guo, Bianqing, Gao, Di, Peng, Guangrong, Yu, Jing, Liu, Weiqing, Wang, Guangxu, Li, Quan, Zhang, Bo, Wu, Wei
• Format: Article
• Language: English
• Subjects: Astronomical time scale; Milankovitch cycle; Miocene; Paleo-water depth
• ISSN: 0031-0182
• DOI: 10.1016/j.palaeo.2025.112736

The Miocene was a period influenced by significant changes in global climate. During the Middle Miocene Climate Optimum (MMCO), greenhouse gas concentrations and temperatures are presumed to have been similar to those projected under current scenarios of continued temperature rise, whereas following the MMCO, there was a marked decline in temperatures, coinciding with the Middle Miocene Climate Transition (MMCT). However, the patterns of sea levels, sedimentary environments, and biological responses to these extreme climatic shifts have yet to be sufficiently determined. The Pearl River Mouth Basin, a sedimentary basin located in the northern part of the South China Sea, contains extremely thick strata rich in microfossils from the Miocene, thereby making it an excellent location for studying the climate–environment–paleontological responses during this period. In this study, by synthesizing microfossil and Milankovitch cycle dating based on well-cuttings and well-logging data, we establish a high-precision astronomical time scale (ATS) (17.54–7.8 Ma), and subsequently reconstructed the paleo-water depth of the region using a combination of a sedimentary noise models and the percentage planktonic foraminifera method, revealing a general deepening trend from 17.54 to 7.8 Ma, which was significantly influenced by regional tectonic activity. On a timescale of 1–2.5 Ma, we identified six major transgression–regression processes, occurring between 17.54 and 15.8, 15.8 and 14.1, 14.1 and 12.2, 12.2 and 10.0, 10.0 and 8.9, and 8.9 and 7.8 Ma, respectively, all of which were strongly influenced by the paleoclimate. The diversity of foraminifera was found to be significantly affected by paleo-water depth, but there was a lag relative to paleo-water depth. During the MMCT period, the paleo-water depth decreased significantly, from 256 m at 14.35 Ma to 38 m at 14.11 Ma under the influence of paleoclimate. Some foraminifera did not adapt to the environmental changes and became extinct. Those that adapted to the new environment thrived rapidly, and the response lag time of the foraminifera was approximately 0.4 Ma. Our findings in this study indicate that there are certain coupling relationships among climate, environment, and living organisms, which can provide a new historical perspective for understanding the current global changes attributable to anthropogenic activities. •A high-precision astronomical time scale established by integrating micropaleontology and Mil