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A Floating Astronomical Time Scale for the Early Late Cretaceous Continental Strata in the Songliao Basin, Northeastern China
Author(s) -
MA Xiaojuan,
WU Huaichun,
FANG Qiang,
SHI Meinan,
ZHANG Shihong,
YANG Tianshui,
LI Haiyan,
WANG Chengshan
Publication year - 2020
Publication title -
acta geologica sinica ‐ english edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.444
H-Index - 61
eISSN - 1755-6724
pISSN - 1000-9515
DOI - 10.1111/1755-6724.14497
Subject(s) - geology , cyclostratigraphy , cretaceous , borehole , paleontology , chronostratigraphy , biozone , milankovitch cycles , structural basin , paleoclimatology , lithostratigraphy , geologic time scale , climate change , glacial period , oceanography
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 (K 2 q ), Qingshankou (K 2 qn ), Yaojia (Ky and Nenjiang (K 2 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 K 2 n , K 2 y , K 2 qn and K 2 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 K 2 qn and K 2 y . Nevertheless, our ATS of K 2 n 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.