Congratulations to Meng Wang and his co-authors!
His first EPSL (Earth and Planetary Science Letters) paper entitled "Astronomical forcing and sedimentary noise modeling of lake-level changes in the Paleogene Dongpu Depression of North China" is online now.
Meng is a visiting Ph.D. student at Penn State from China University of Geosciences, Wuhan. He is now working with me on the development of sedimentary noise modeling and the reconstruction of lake levels in the deep time.
Astronomical forcing and sedimentary noise modeling of lake-level changes in the Paleogene Dongpu Depression of North China
Meng Wang, Honghan Chen, Chunju Huang, David B. Kemp, Tianwu Xu, Hongan Zhang, & Mingsong Li
• We provide a 14.7-Myr long astrochronology for the Paleogene Shahejie Formation.
• Statistical method helps track changes in sedimentation rate and depositional environment.
• Sedimentary noise modeling of lacustrine strata is used for paleolake level reconstruction.
• Long-term (∼4.8 Myr, 2.4 Myr and 1.2 Myr) astronomical forcing had a significant impact on lake-level variations.
Challenges in interpreting continental sequence stratigraphy and typically uncertain geochronology hinder the understanding of paleolake evolution and hydrocarbon exploration in terrestrial basins. The Dongpu Depression in North China is a lacustrine basin with abundant hydrocarbon resources. An accurate chronology for the Paleogene stratigraphy in the Dongpu Depression is lacking, and the mechanism of lake-level variation remains unclear. In this study, we utilize high-resolution gamma ray logs to conduct a cyclostratigraphic analysis of the Shahejie Formation, which is a Paleogene succession in the Dongpu Depression characterized by sandstones and dark mudstones interbedded with thin salt rocks. Time series analysis reveals evidence for 405 kyr eccentricity cycles in the gamma ray series, which is supported by statistical modeling of optimal sedimentation rates. Tuning of the gamma ray data to this 405 kyr eccentricity cyclicity enables a 14.7-Myr-long astronomical time scale to be constructed. This astrochronology is anchored to the astronomical age of the Dongying Formation/Shahejie Formation boundary (28.86 Ma) in the Bohai Bay Basin, thus providing an absolute timescale for the studied interval that extends from 28.86 Ma to 43.59 Ma. Using this anchored astrochronology, we show that a recently established sedimentary noise model for inferring sea level change in marginal marine settings can be used to similarly infer lake level fluctuations in terrestrial basins. In particular, sedimentary noise modeling of the tuned gamma ray series reveals high-resolution changes in sedimentary noise that are indicative of lake-level variations linked to million-year scale (i.e., ∼4.8 Myr, 2.4 Myr and 1.2 Myr) astronomical forcing. These inferred changes in lake level are supported by previously published sequence stratigraphic interpretations. Moreover, an evolutionary correlation coefficient (eCOCO) analysis of the gamma ray series also indicates recurrent distortions in sedimentation that may be linked to lake level changes. This study provides new methods for the assessment of paleolake level variations, as well as insights into the connection between astronomical forcing and lake evolution across long timescales in terrestrial basins.
Global climate changes, sea level and lake level dynamics during the Paleogene (Wang et al., 2020 EPSL).
(A) Tuned GR time series (black) with 405-kyr filtered output (red). (B) Composite benthic foraminiferal oxygen isotope (δ18O) record from Cramer et al. (2009). (C, D) ρ1 and DYNOT models of tuned GR series from Fig. 6. (E) Global sea level modified from Snedden and Liu (2010). (F) Earth’s obliquity solution (grey, Laskar et al., 2004) and its 1.2 Myr AM cycles (red) shown with filtered 1.2 Myr cycles (passband: 0.00083 ± 0.00017 cycles/kyr) from ρ1 (purple) and DYNOT (blue) models. (G) Antarctic ice sheet dynamics from Zachos et al. (2001). (H) Earth’s eccentricity solution (grey, Laskar et al., 2004) and its 2.4 Myr AM cycles (red) and 4.8 Myr AM cycles (dashed red) shown with filtered 2.4 Myr cycles (passband: 0.000417 ± 0.0001 cycles/kyr) from ρ1 (purple) and DYNOT (blue) models. (I) Reported long astronomical cycles during the Paleogene. B11: Benthic foraminiferal δ18O of ODP Site 1218 (P.like et al., 2006) and its 1.2 Myr cycles (Boulila et al., 2011); J06: Magnetic susceptibility (MS) and its 1.2 Myr cycles (Jovane et al., 2006); V20: Ca/Fe curve (Vahlenkamp et al., 2020); and WR13: Fe series and recognized 2.4 Myr cycle minima (Westerhold and R.hl, 2013). (J) Dongpu Depression sequence stratigraphy (Gao et al., 2011) comparable with filtered 4.6-Myr cycles (passband: 0.00022 ± 0.00005 cycles/kyr) of the median output of the DYNOT (blue) and ρ1 (purple) results. Warm intervals in Liu et al. (2018a) are shaded with orange bars and the Oi-1 event marked with a cyan bar (A-D).