Quantitative reconstruction of paleowind strength based on ancient marine longshore bars: A case study of the Pinghu Formation in Pingbei slope zone, Xihu Sag

Abstract

Paleowind is an important paleoclimate parameter, but its study has been limited due to the lack of research methods. Recently, some researchers have proposed a method combining wind fields, waves, and the scale of ancient bar sand bodies to indirectly reconstruct paleowind. However, this method can only be used in lacustrine environments since in existing reconstruction methods, the fetch—a necessary parameter approximating the distance that wind blows—is difficult to obtain in marine environments. This study introduces the concept of “fully developed waves”, eliminating the need of fetch, which improves the current method of reconstructing paleowind using bars and extends its application to marine environments. The method is easy to operate and it only needs two parameters: the thickness of longshore bars and the seabed slope. This study further focuses on the bars of the Pinghu Formation in the Pingbei slope zone of the Xihu Sag within the East China Sea Shelf Basin. Using the proposed method, the paleowind variations during the depositional period (37.2–35.5 Ma) were reconstructed. The results show that the Xihu Sag was primarily influenced by easterly winds during this time, with wind speeds ranging from 8.76 to 19.71 m/s. This method removes the limitation of using bars for quantitative paleowind reconstruction exclusively in lacustrine settings, thereby enhancing its application potential and contributing to providing more data for paleoclimate reconstruction.