Research On Stratigraphic Integrity Based On Astronomical Period Identification Of Upper Paleozoic In Dongpu Depression

Using the astronomical period method to study the integrity of stratigraphic profiles is the first in the history of geoscience research,which is compared with the qualitative estimation method of fossil fossils,paleomagnetic method,the thickness of the research profile and the global average of the same period.Methods such as the ratio of sediment thickness,the ratio method of long-term deposition rate and short-term deposition rate of formation profile have the advantages of high accuracy and convenient calculation.In this paper,the Upper Paleozoic strata in Dongpu depression are mainly used for research.The natural gamma logging curves closely related to the changes of the sedimentary environment are analyzed by technical methods such as frequency spectrum analysis and wavelet transform.Sedimentation rate and stratum recovery studies,the results show that:The Upper Paleozoic strata in Dongpu depression can be divided into 6 sets of strata from bottom to top,including Benxi Formation,Taiyuan Formation,Shanxi Formation,Lower Shihezi Formation,Higher Shihezi Formation and Shiqianfeng Formation.Among them,the Benxi Formation and the Taiyuan Formation mainly developed barrier coastal systems,and locally developed limited platform facies;the sedimentary environment of the Shanxi Formation was mainly delta depositional systems;while the upper and lower Shihezi Formation strata were the most developed delta facies;the Shiqianfeng Formation strata were rivers.The lake sedimentary system is the main one.Using wavelet transform,frequency spectrum analysis and other means to study the logging curves of the Upper Paleozoic strata in Dongpu depression,it was found that the ratio of the theoretical earth orbit parameters(short eccentricity:slope:precession=5:2:1)The thickness of stratigraphic cycle with good agreement.It shows that the sedimentary cycle of the Upper Paleozoic is controlled by the astronomical orbital driving force.By this method,we calculated the respective deposition time limits of the six sets of Upper Paleozoic strata:the deposition time of the Benxi Formation is 270 ka,the Taiyuan Formation is 1280 ka,and the Shanxi Formation is 1050 ka.The deposition time of the Lower Shihezi Formation is 940 ka,the deposition time of the Upper Shihezi Formation is 2100 ka,and the deposition time of the Shiqianfeng Formation is 2450 ka.Six sets of formations in the Upper Paleozoic were further divided by wavelet transform,and each section of the further division was analyzed separately to calculate the deposition rate of each section.The analysis results show that the deposition rate of these six sets of formations varies greatly.The lowest deposition rate is the middle section of the Taiyuan Formation 2240～2270m.The deposition rate is 0.081m/ka,and the highest deposition rate is the middle section of the Upper Shihezi Formation 1669～1789m.Location,its deposition rate is 0.222m/ka.Using the method of stratum integrity equal to the ratio of long-term deposition rate to short-term deposition rate of the stratum profile,the integrity of the six sets of strata in the studied area was analyzed and found that the sedimentary environment is closely related to the stratum integrity:the delta plain subfacies sedimentary strata have the highest integrity,The integrity of the fluvial sedimentary strata is second,the sedimentary facies ranked third is the delta front subfacies,the stratum integrity is the stratum formed in the barrier coastal system.Based on the astronomical astronomical cycle,the deposition process of the Upper Paleozoic strata was restored,which proved that during the formation of the Upper Paleozoic strata,the deposition rate of the Benxi Formation and Taiyuan Formation was low,the integrity was poor,and there were many depositional discontinuities during the formation process,indicating this period of time the sedimentary environment is very unstable;the deposition rate of the Shanxi Formation and the Lower Shihezi Formation is medium and the integrity is high,indicating that the depositional environment is very stable during this period;the formation deposition rate of the Upper Shihezi Formation and the Shiqianfeng Formation is medium,and the formation integrity is medium,indicating that this section The time deposition environment is relatively stable.