Title: Seepage-induced sedimentary structures and their significance in beach bars of the Zhoushan Archipelago, China

Authors: Qiheng Guo; Junlin Chen; Dirk Knaust; Shuting Shi; Xiangli Shi; Zhenkui Jin; Chenglin Liu

Addresses: College of Geosciences, China University of Petroleum, Beijing, 102249, China; Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an, 710018, China ' Key Laboratory of Petroleum Resources, Gansu Province, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou 730000, Gansu, China; University of Chinese Academy of Sciences, Beijing 100049, China ' Equinor ASA, 4035, Stavanger, Norway ' Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an, 710018, China ' Exploration and Development Research Institute of PetroChina Changqing Oilfield Company, Xi'an, 710018, China ' College of Geosciences, China University of Petroleum, Beijing, 102249, China ' College of Geosciences, China University of Petroleum, Beijing, 102249, China

Abstract: Sedimentary structures induced by water seepage are described from modern beach bars within the Zhoushan Archipelago in China, including two unique types, herein referred to as: 1) seepage tubes; 2) seepage beads. Their formation is related to water seepage in sandy sediments, where the seepage tubes are formed by the downward seepage of pore water in sandy sediment, while the seepage beads are formed by the vertical superposition of multiple beaded horizontal seepage layers. The results show that unique terrain and rapid water ingress and retreat related to tides control the formation of these sedimentary structures. The seepage-induced sedimentary structures can be divided into vertical vadose belts that develop seepage tubes, horizontal undercurrent belts with seepage beads, and water-table variation belts with both seepage tubes and seepage beads appearing alternately. These sedimentary structures are hitherto undescribed and contribute to an improved understanding of similar sedimentary structures in the geological record. [Received: April 3, 2024; Accepted: July 7, 2024]

Keywords: sedimentary structures; water seepage; seepage tubes and beads; beach bar; Zhoushan Archipelago; China.

DOI: 10.1504/IJOGCT.2025.146530

International Journal of Oil, Gas and Coal Technology, 2025 Vol.37 No.4, pp.381 - 396

Received: 22 Mar 2024
Accepted: 07 Jul 2024
Published online: 02 Jun 2025 *

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