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Spectrogram analysis of seven natural gamma-ray logging of Member 1 of the Qingshankou Formation(K_2qn~1)and Member 1 and 2 of the Nenjiang Formation(K_2n~(1-2))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 K_2qn~1 sections,and～6.69-10.16 cm/ka for the K_2n~(1-2) sections.Two marine transgression events occurred during the deposition of K_2qn~1 and K_2n~(1-2) 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 Songllao Basin may provide great potential for high-resolution stratigraphic subdivisions and correlations.
Spectrogram analysis of seven natural gamma-ray logging of Member 1 of the Qingshankou Formation (K_2qn ~ 1) and Member 1 and 2 of the Nenjiang Formation (K_2n ~ (1-2)) 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 K_2qn ~ 1 sections and ~ 6.69-10.16 cm / ka for the K_2n ~ (1-2) sections.Two marine transgression events occurred during the deposition of K_2qn ~ 1 and K_2n ~ (1-2) and their ages 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 Songllao Basin may provide great potential for high-resolution stratigraphic subdivisions and correlations.