Extraction of astronomical cycle signals and identification of third-order sequences in the Ordovician of Well XT1,southern margin of Ordos Basin
In the southern margin of the Ordos Basin,no cyclostratigraphic analysis has yet been conducted on the Paleozoic Ordovician to identify astronomical orbital cycle signals.This analysis is crucial for establishing a high-precision geological timescale and reasonably dividing third-order sequences,which is of significant importance for oil and gas exploration in the area.Combining cyclostratigraphic theory and signal decomposition techniques,a cyclostratigraphic analysis of the Paleozoic Ordovician in the Well XT1 was performed.The results indicate that there are differences in sedimentation rates among different strata.The sedimentation rate during the Yeli and Liangjiashan stages in Well XT1 area ranges from 4.2 to 5.6 cm/ka,while the Majiagou stage varies between 2.2 and 5.5 cm/ka.The sedimentation rate during the Pingliang and Beiguoshan stages increases,ranging from 4.3 to 9.3 cm/ka.Significant Milankovitch cycle signals are present in the Ordovician of Well XT1,recording eccentricity and obliquity astronomical orbital periods.A 405 ka eccentricity cycle was used to establish an age model for astronomical tuning,creating a fluctuating astronomical timescale for the Ordovician in Well XT1,with the sedimentation period for the Yeli to Liangjiashan Formations at approximately 3.25 Ma,and for the Majiagou to Beiguoshan For-mations at around 27.4 Ma.Using wavelet transformation,the frequency of the Ordovician third-order se-quences was primarily distributed around 0.011 cycles/m,allowing the division of the Ordovician in Well XT1 into approximately 13 third-order sequences.This study provides a new quantitative method and scien-tific basis for the division of Ordovician sequences and the study of astronomical cycles,contributing to a refined understanding of sedimentary processes and the accuracy of timescales.
万方数据
维普
