| 18 Dec 2025
The Nenjiang Formation responses to astronomically forced climate changes during the Upper Cretaceous in the Gulong Area, Songliao Basin, NE China
Abstract. The Songliao Basin preserves a complete Cretaceous continental sedimentary succession. Previous researchers have conducted extensive cyclostratigraphic studies on the Upper Cretaceous Nenjiang Formation, but paleoclimatic research has primarily focused on the lower part of the formation. The relationship between climatic changes and astronomical parameters in the middle and upper sections of the Nenjiang Formation has not yet been fully investigated. This study conducted cyclostratigraphic analysis of the second to third members of Nenjiang Formation Late Cretaceous (K2n2-3) in the Songliao Basin using high-resolution gamma-ray logging (GR) data, while also performing paleoclimatic analysis in conjunction with palynological data. The fossil spores and pollen from the K2n3 indicate a geological age of the Late Cretaceous Campanian. Based on the ecological data of the parent plants of the spores and pollen, the vegetation types, climatic zones, and humidity types of the lower part of the K2n3 were analyzed, confirming its semi-warm and semi-humid paleoclimatic characteristics. Time-series analysis reveals persistent 405-kyr (long eccentricity), 95-kyr (short eccentricity), 38.3-kyr (obliquity), and 22.8-kyr (precession) sedimentary cycles, further validated by an optimal sedimentation rate model. We established a 3.24-Myr floating astronomical time scale for K2n2-3 by tuning the GR series to orbital targets. This timescale is anchored by a volcanic ash age (83.269 ± 0.044 Ma) at the K2n2 base, generating an absolute age framework spanning 83.33–80.00 Ma. Vertical transitions in palynofloral assemblages correspond to the 38.3-kyr obliquity cycle, indicating significant obliquity forcing on regional paleoclimate dynamics.
1. The work is scientific. However, the paper is similar to a company report. The results, if verifiable (see below), are of a local interest. If the authors have compared their results with other results of similar age and/or similar geological settings, the results may be of interests to a world-wide audience, and the impact of the research can be elevated.
2. The original data is absent, so the results cannot be verified. In addition, the geologic interpretation, such as lithology, depositional environment, and cyclostratigraphy, is not present.
3. A gamma-ray curve, which were a proxy for lithology, was input to an algorithm. And spectral results and estimate of sedimentation were produced. Interpretation of climate and astrostratigraphy was followed. No discussions on the procedures and parameter selections of quantitative analyses. No discussions on the validity and uncertainties of the results. As a result, the readers, including me as a reviewer, may think it is garbage-in and garbage-out.
For example, it appears that the 405-ky filtered cycles cannot be identified/visually seen on the gamma curve. But this cycle is used to establish a floating astro-stratigraphy. Why not using the obliquity or 100-ky eccentricity cycles? On the other hand, there is a discrepancy when trying to correlate the palynological data with the filtered obliquity cycles (see my comments on the figure in the attached file).
4. The palynological data and interpretation are only for a very short interval of ~8 m. The interpretation is over-simplified and extrapolated to the entire interval of ~400 m. This is too over-reaching.
5. If the palynological data is discounted, the only data is a gamma-ray curve, which is not presented and described. The source of data is too limited in amount and quality (?). The quality is hard to assess because the data is not presented.
6. See many comments and suggestions in my comments attached to the manuscript.
7. My recommendation is "major revisions" or "rejected."