Late Santonian-early Campanian lake-level fluctuations in the Songliao Basin, NE China and their relationship to coeval eustatic changes

In the present study, we present lake-level fluctuations in Members 1 and 2 of the Nenjiang Formation (late Santonian-early Campanian) in the Songliao Basin that are indicated by basin-scale correlations of Fischer Plots based on natural gamma-ray logging data. Meanwhile, the Al/K ratios of the SK1 core indicate that changes in precipitation forced lake-level fluctuations in the basin. Compared to global sea-level changes, lake-level fluctuations show an out-of-phase relation with sea-level variations in the lacustrine phase of the basin, suggesting that climate-driven water transport between continents and oceans controlled short-term sea-level changes in the late Santonian-early Campanian. During the phase of marine-lake connectivity (basal Nenjiang Member 1), although the marine regression-driven decrease in lake-level corresponds to salinity stratification and strongly reducing water conditions, increasing precipitation in the basin implies that the hydrological cycle transported more water from the oceans toward continents. Based on the results we suggest that limno-eustasy controlled water levels in the Songliao basin in the late Santonian-early Campanian.