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<p>Cyclostratigraphic division in fine-grained sedimentary strata provides a fundamental basis for oil and gas exploration in such deposits. With continued research, increasing complexity and variability in cyclostratigraphic indicators and analytical methods have led to growing divergence and controversy in interpretations. To optimize cyclostratigraphic analysis approaches and identify suitable sedimentary sequence proxy indicators, this study focuses on lacustrine shale of the upper sub-member of the 4th member of the Paleogene Shahejie Formation (Es<sub>4</sub><sup>scs</sup>) in Well Niuye 1, Dongying Sag, Jiyang Depression, Bohai Bay Basin. Multi-source datasets, including geophysical logs, geochemical elements, environmental magnetic parameters, and core grayscale records, were integrated and analyzed using two time-series analysis methods, TSAM1 and TSAM2. Results show that TSAM2 performs better in cyclostratigraphic identification for most datasets, including natural gamma ray, acoustic logging, elemental concentrations, magnetic susceptibility, and core grayscale. Core grayscale data further enable recognition of cycles shorter than the precession scale. Comprehensive comparison indicates that natural gamma ray logging represents the most effective sedimentary sequence proxy indicator, while TSAM1 is identified as the most suitable time-series analysis method. Based on this framework, complete Milankovitch cycles were identified within the study interval, including 5 long eccentricity cycles of 405 kyr, 22 short eccentricity cycles of 95.24kyr, 48 obliquity cycles of 39.76kyr, 53 obliquity cycles of 38.54kyr, 87 precession cycles of 23.28kyr, 98 precession cycles of 22kyr, and 107 precession cycles of 18.82kyr. Total depositional duration is estimated at approximately 2.038 Ma, with an average sedimentation rate of about 0.074 m/kyr. These results provide methodological support for high-precision cyclostratigraphic division and construction of astronomical timescales in continental fine-grained sedimentary strata, contributing to advancement of fine-grained sedimentary cyclostratigraphy.</p>

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Analysis method and indicator optimization of astronomical cycles in lacustrine fine-grained sedimentary strata-a case study of the Es4scs in well niuye 1, Dongying Sag, Jiyang Depression, Bohai Bay Basin

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  • 发表日期：

    2026年4月16日

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  • Ledan Yu,
  • Jiao Wang,
  • Jun Peng

摘要

Cyclostratigraphic division in fine-grained sedimentary strata provides a fundamental basis for oil and gas exploration in such deposits. With continued research, increasing complexity and variability in cyclostratigraphic indicators and analytical methods have led to growing divergence and controversy in interpretations. To optimize cyclostratigraphic analysis approaches and identify suitable sedimentary sequence proxy indicators, this study focuses on lacustrine shale of the upper sub-member of the 4th member of the Paleogene Shahejie Formation (Es4scs) in Well Niuye 1, Dongying Sag, Jiyang Depression, Bohai Bay Basin. Multi-source datasets, including geophysical logs, geochemical elements, environmental magnetic parameters, and core grayscale records, were integrated and analyzed using two time-series analysis methods, TSAM1 and TSAM2. Results show that TSAM2 performs better in cyclostratigraphic identification for most datasets, including natural gamma ray, acoustic logging, elemental concentrations, magnetic susceptibility, and core grayscale. Core grayscale data further enable recognition of cycles shorter than the precession scale. Comprehensive comparison indicates that natural gamma ray logging represents the most effective sedimentary sequence proxy indicator, while TSAM1 is identified as the most suitable time-series analysis method. Based on this framework, complete Milankovitch cycles were identified within the study interval, including 5 long eccentricity cycles of 405 kyr, 22 short eccentricity cycles of 95.24kyr, 48 obliquity cycles of 39.76kyr, 53 obliquity cycles of 38.54kyr, 87 precession cycles of 23.28kyr, 98 precession cycles of 22kyr, and 107 precession cycles of 18.82kyr. Total depositional duration is estimated at approximately 2.038 Ma, with an average sedimentation rate of about 0.074 m/kyr. These results provide methodological support for high-precision cyclostratigraphic division and construction of astronomical timescales in continental fine-grained sedimentary strata, contributing to advancement of fine-grained sedimentary cyclostratigraphy.