AUTHOR=Liu Siqi , Zhang Changmin , Zhu Rui , Li Jinchi , Wang Zeyu 

TITLE=Thickness Variation Characteristics of Tidal Rhythmites—An Example From the Pinghu Formation, Xihu Sag, East China Sea Shelf Basin

JOURNAL=Frontiers in Earth Science

VOLUME=Volume 10 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/earth-science/articles/10.3389/feart.2022.698061

DOI=10.3389/feart.2022.698061

ISSN=2296-6463

ABSTRACT=The Pinghu Formation of Xihu Sag in the East China Sea Shelf Basin is obviously affected by tidal action，but there are fewstudies on its tidal rhythmites. Through detailedobservation and description of the core, this paper studies the periodicity of the tidal rhythmites of well A-11 by using the grayscale measurement of digital images based on MATLAB, spectral analysis and wavelet transform. According to the statistical data series of millimeter lamination thickness, the sandy laminae thickness, the argillaceous laminae thickness and the couplet thickness were quantitatively compared and analyzed, and the main controlling factors of different thickness cycles were discussed. Studies have shown that the periodicity of sandy laminae, argillaceous laminae and couplet thickness have certain differences, which are due to the influence of related factors such as the nature and magnitude of tidal current cycles at the time of deposition. The high frequency signal represents the event deposition, the middle frequency signal represents the tidal current deposition, and the low frequency signal highlights the change of sedimentary facies. Therefore, the change of couplet thickness is the result of the comprehensive influence of event deposition, tidal current deposition and the change of sedimentary facies belt. As a preliminary attempt to study tidal rhythmites in this study area, the thickness variation of sandy laminae, argillaceous laminae and couplets in tidal deposits is explored by measuring the thickness of these three layers, which provides a certain reference value for the reconstruction of tidal sedimentary environment in paleostratigraphic sequence.