中国科学院南京地质古生物研究所机构知识库

Charophyte assemblages from the mid-Campanian and lower Paleocene of the SK-1(North) borehole in the Songliao Basin (NE China) are here re-studied. Four charophyte biozones and one superzone are defined in the Sifangtai and Mingshui formations and correlated to the Geomagnetic Polarity Time Scale. These include a mid-late Campanian Atopochara trivolvis ulanensis Zone, a latest Campanian - early Maastrichtian Microchara gobica Zone, a late Maastrichtian Microchara prolixa Zone, and an earliest Danian Peckichara sinuolata Zone. The latter three zones are grouped within the Microchara cristata Superzone, which allows intra- and intercontinental correlation with other basins in China and Europe. Peckichara sinuolata first appears in chron C29r (upper Mingshui Formation) and is proposed as the basal marker of the Paleocene. The biozonation of the K/Pg interval proposed for the Songliao Basin differs from a previous biozonation proposed in the Pingyi Basin since it represents a different biogeographical and palaeoecological context. In the mid-Campanian to Maastrichtian, the flora was limited to freshwater lakes in northern China and Mongolia, whereas in the Pingyi Basin, brackish water dominated. In the Paleocene, the Songliao Basin contained a diverse flora consisting of nine species that thrived in terrigenous and temporary lakes, whereas the flora in the Pingyi Basin was dominated by one species inhabiting permanent alkaline lakes. The species common to the two basins are widely distributed in Eurasia and constitute a useful tool for long-distance correlations, but serve as a less-precise tool for detailed biostratigraphical subdivision within one specific basin.