Palynological evidence of an Early Cretaceous age for the Yixian Formation at Sihetun, western Liaoning, China

Vertebrate-bearing beds in the lower Yixian Formation at the locality of Sihetun in western Liaoning Province, northeast China, have yielded palynomorph assemblages that are dominated by gymnosperm pollen. Triradiate spores are very much subordinate. No unequivocal angiosperm pollen grains were encountered, although there are a few previous records of these products of flowering plants at Sihetun. The possibility that the beds might be late Jurassic rather than early Cretaceous in age is rejected. The palynomorphs are very poorly preserved, with identifications difficult to make and commonly questionable. Nevertheless, there is no evidence to suggest that the assemblages are any older than Valanginian–Hauterivian or Barremian.