PALYNOLOGICAL INSIGHT INTO THE K–PG BOUNDARY IN THE SONGLIAO BASIN, NE CHINA

The SK1(n) borehole in the Songliao Basin (NE China) offers a valuable opportunity to study the Late Cretaceous to Early Paleogene stratigraphy and paleoenvironments, as well as the important subject of the Cretaceous–Paleogene (K–Pg) boundary. Palynology is commonly used as the preferred method for identifying this terrestrial boundary. However, previous palynological work might have lacked sufficient resolution in both sampling and analysis of the detailed vertical change characteristics through the sequence in the Songliao Basin. Here, samples were collected from the SK1(n) borehole for a high-resolution palynomorphological analysis of the upper part of Member 2 of the Mingshui Formation to find evidence of K–Pg extinction events. The results showed that spore and pollen fossils exist above the previously described extinction level. The three relatively abundant samples at the bottom revealed the appearance of the middle Maastrichtian. The evolutionary trend displayed a two-stage disappearance pattern. Moreover, the fossil records indicated that the K–Pg boundary is much higher than previously thought; stratigraphically, it could possibly be above 356.50 m. This is the suggested new boundary based on fossil preservation.