The Late Cretaceous Gastropod Biostratigraphy And Its K/Pg Boundary Biological Evolution In SK1

Songliao Basin holds a key stratigraphic continental strata which provide the opportunity to study the paleoclimatic variations and reconstruction along the Cretaceous Paleogene(K/Pg)boundary on the continental side.The Sifangtai Formation and Mingshui Formation encountered in the Continental Scientific Drilling Institute of Songke 1 Well which spans the Late Cretaceous-Early Paleogene age.Total 10 species of 6 genera of the gastropods were identified and three assemblage zones were established from bottom to top which are Truncatella maxima Yu et LeeCampeloma sp.2(485.44 m-809.77 m),Valvata(Valvata)sinensis Yu et Lee-Plysa sp.(314.80 m-478.27 m)and Viviparus(314.80 m-335.92 m).These gastropods assemblage zones can be compared with other areas globally and K/Pg boundary is identified in the third assemblage zone of Shanghuapira cosata Yu(314.80 m-335.92 m).The gastropods of the north hole of the Songke 1 well were distributed at 314.80m-809.77 m,and no more fossilized fossils were found above 314.80 m.The Viviparus sp.genus with obvious Paleocene color was found at 335.92 m in the third combination zone,and late Cretaceous characteristic molecules were also developed on this genus.It is speculated that the third combination zone may have late the transitional color of the Cretaceous-Early Paleocene.