| A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China |
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| 作者姓名： | MA Xiaojuan WU Huaichun FANG Qiang SHI Meinan ZHANG Shihong YANG Tianshui LI Haiyan WANG Chengshan |
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| 摘 要： | A continuous terrestrial succession was recovered from the Songke-2(SK-2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke-1(SK-1) core. In this study, thorium(Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi-periodically; power spectra and evolutionary fast Fourier transformation(FFT) analysis reveal significant cycles in the Quantou(K2 q), Qingshankou(K2 qn), Yaojia(K2 y) and Nenjiang(K2 n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity(405 kyr), short orbital eccentricity(100 kyr), obliquity(37 kyr), and precession cycles(22.5 kyr and 18.4 kyr). The durations of the K2 n, K2 y, K2 qn and K2 q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ～18.62 Myr "floating" astronomical time scale(ATS). Comparison of the durations between the SK-1 s and SK-2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2 qn and K2 y. Nevertheless, our ATS of K2 n supports the chronostratigraphic frame constructed by the CA-ID-TIMS data of the SK-1 s borehole. This new "floating" ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems.
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| 收稿时间： | 2019/11/29 0:00:00 |
| 修稿时间： | 2020/1/13 0:00:00 |
A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin,Northeastern China |
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| Authors: | MA Xiaojuan WU Huaichun FANG Qiang SHI Meinan ZHANG Shihong YANG Tianshui LI Haiyan and WANG Chengshan |
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| Institution: | 1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China
2 State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China
2 State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China
2 State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China
2 State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China,1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China and 1 Schoolof Ocean Sciences, China University of Geosciences, Beijing 100083, China |
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| Abstract: | A continuous terrestrial succession was recovered from the Songke‐2 (SK‐2) borehole in the Songliao Basin, Northeastern China. This borehole provides a unique material for further research on the continental paleoclimate during Cretaceous greenhouse period, following a series of achievements of the Songke‐1 (SK‐1) core. In this study, thorium (Th) logging data were chosen as a paleoclimate proxy to conduct a detailed cyclostratigraphic analysis. The Th series varies quasi‐periodically; power spectra and evolutionary fast Fourier transformation (FFT) analysis reveal significant cycles in the Quantou (K2q), Qingshankou (K2qn), Yaojia (Ky and Nenjiang (K2n) formations. The ratio of cycle wavelengths in these stratigraphic units is approximately 20:5:2:1, corresponding to long orbital eccentricity (405 kyr), short orbital eccentricity (100 kyr), obliquity (37 kyr), and precession cycles (22.5 kyr and 18.4 kyr). The durations of the K2n, K2y, K2qn and K2q are estimated as 6.97, 1.83, 5.30 and 4.52 Myr, respectively, based on the constructed ～18.62 Myr “floating” astronomical time scale (ATS). Comparison of the durations between the SK‐1 s and SK‐2 boreholes exhibits a slight difference of 0.06 Myr and 0.459 Myr for K2qn and K2y. Nevertheless, our ATS of K2n supports the chronostratigraphic frame constructed by the CA‐ID‐TIMS data of the SK‐1s borehole. This new “floating” ATS provides precise numerical ages for stratigraphic boundaries, biozones and geological events in the Songliao Basin, and can serve as a basis for correlation of strata and events between marine and terrestrial systems. |
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| Keywords: | Late Cretaceous SK-2 borehole cyclostratigraphy astronomical time scale Songliao Basin northeastern China |
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