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Recognition of Milankovitch Cycles in the Natural Gamma–Ray Logging of Upper Cretaceous Terrestrial Strata in the Songliao Basin

Abstract: Spectrogram analysis of seven natural gamma‐ray logging of Member 1 of the Qingshankou Formation (K2qn1) and Member 1 and 2 of the Nenjiang Formation (K2n1–2) of Late Cretaceous age in the Songliao Basin reveals sedimentary cyclicities controlled by Milankovitch climate periodicities. The recognition of Milankovitch cycles allows estimation of an average accumulation rate of ∼7.55‐8.62 cm/ka for the K2qn1 sections, and ∼6.69‐10.16 cm/ka for the K2n1–2 sections. Two marine transgression events occurred during the deposition of K2qn1 and K2n1–2 and their ages are at ∼0.74‐1.10 Ma and ∼2.38‐4.84 Ma, respectively. Identification of Milankovitch cycles from fine‐grained deep lake sedimentary rocks in the Songliao Basin may provide great potential for high‐resolution stratigraphic subdivisions and correlations.