地质科技通报2025，Vol.44Issue(4)：288-303,16.DOI:10.19509/j.cnki.dzkq.tb20230546
黔西南下石炭统打屋坝组页岩的天文旋回识别及层序地层划分
Orbital cycle recognition and sequence stratigraphic division of the Lower Carboniferous Dawuba Formation shales in Southwest Guizhou
摘要
Abstract
The Lower Carboniferous Dawuba Formation in Southwest Guizhou hosts a shale sequence with significant exploration potential.Current disagreements regarding its sequence division scheme and developmental mechanisms have somewhat hindered the understanding of the spatial distribution patterns of this high-quality shale.[Objective]Therefore,this study focuses on the Lower Carboniferous Dawuba Formation shale(interval 1 457-2 466 m)from the Well Qian Shui Di-1 in Southwest Guizhou.[Methods]Utilizing the natural gamma ray(GR)log as a proxy indicator,methods including time series analysis,INPEFA(integrated noise-enhanced population evolutionary frequency analysis),and wavelet analysis were applied to conduct cyclostratigraphic and sequence stratigraphic investigations.The aim is to achieve a"quantitative"division of the sequence stratigraphy for this shale unit from an astronomical forcing perspective.[Results]The results demonstrate that the Dawuba Formation shale records clear astronomical periodic signals.COCO(correlation coefficient)analysis estimates an optimal average sedimentation rate of 16.4 cm/ka,corresponding to a sediment thickness of 66.42 m for the 405 ka long eccentricity cycle.Spectral analysis and astronomical tuning were performed on segmented GR data from the Well Qian Shui Di-1(upper segment:1 457-1 932 m;lower segment:1 932-2 466 m).The optimal sedimentation rates for the upper and lower segments are 16.5 cm/ka and 11.2 cm/ka,respectively.The entire Dawuba Formation recorded 19 long eccentricity cycles,enabling the establishment of a"floating"astronomical time scale,which estimates a total duration of approximately 7.86 Ma for the formation.Furthermore,relative sea-level change curves were reconstructed using sedimentary noise modeling(DYNOT and ρ1 methods).Building upon the temporal framework established by cyclostratigraphy,and integrating relative sea-level extrema,INPEFA,and wavelet analysis results,six third-order sequence boundaries were identified,dividing the formation into five third-order sequences.The development of these third-order sequences is interpreted to be controlled by a stable approximately 1.2 Ma obliquity amplitude modulation cycle.[Conclusion]By applying cyclostratigraphy to the sequence division of the Dawuba Formation shale,this study explores the relationship between astronomical orbital parameters and relative sea-level change at different temporal scales,achieving the division of both third-order and fourth-order sequences.This methodology enables potential high-resolution(10 000-year scale)chronostratigraphic correlation of marine shales.It provides a refined temporal framework for predicting intervals of high-quality source rock development within shale sequences,thereby offering crucial theoretical guidance for shale oil and gas exploration.关键词
旋回地层学/时间序列分析/层序地层学/海平面变化/斜率调幅/页岩/黔西南Key words
cyclostratigraphy/time series analysis/sequence stratigraphy/sea-level change/obliquity amplitude modulation/shale/Southwest Guizhou分类
天文与地球科学引用本文复制引用
王嘉伟,金思丁,魏祥峰,郝景宇,陈义才,李露艳,马超..黔西南下石炭统打屋坝组页岩的天文旋回识别及层序地层划分[J].地质科技通报,2025,44(4):288-303,16.基金项目
国家自然科学基金项目(42172137) （42172137）
