Late Cretaceous stratigraphic division in the northwestern Songliao Basin, Northeast China: Evidence from palaeontology and palaeomagnetism

This paper combines new palaeomagnetic studies, palaeontological dating, and sedimentary analyses to propose a modified stratigraphic classification scheme in the northwestern Songliao Basin, which is of great significance for stratigraphic correlation, sedimentation analysis, basinal subsidence, and oil and gas exploration. New palaeontological and palaeomagnetic evidence redefined a group of semi-consolidated lacustrine strata, buried beneath the Quaternary Yaluhe Formation on the Western Slope of the Songliao Basin, as Late Cretaceous, not the Middle Pleistocene. The chronostratigraphic framework re-evaluates its stratigraphic age as late Coniacian to early Campanian (Late Cretaceous), between 83 and 85 Ma. Sedimentation research from 17 boreholes on the Western Slope of the Songliao Basin displays that the semi-consolidated strata successively experienced lacustrine and delta facies deposits. Comparison of this new stratigraphy with the Late Cretaceous sequences on the adjacent Central Depression of the Songliao Basin reveals significant variations in lithology and palynological assemblages. Three new palynological assemblages are also reported from the Late Cretaceous sequences of the Songliao Basin.

Automated summary

This paper presents a revised stratigraphic classification for the northwestern Songliao Basin based on new paleomagnetic studies, paleontological dating, and sedimentary analyses. The study is of great importance for stratigraphic correlation, sedimentation analysis, basinal subsidence, and oil and gas exploration. The results show that the semi-consolidated lacustrine strata, previously believed to be of Middle Pleistocene age, are actually Late Cretaceous. The new chronostratigraphic framework places these strata as late Coniacian to early Campanian, with an age between 83 and 85 Ma. Sedimentation research from 17 boreholes reveals the successive deposition of lacustrine and delta facies deposits in the area.