Palynomorph assemblages from the Fenghuoshan Group, southern Qinghai, China: their age and palaeoenvironmental significance

The varicoloured Fenghuoshan Group occurs widely in the Qiangtang-Hoh Xil region of the northern Qinghai-Xizang Plateau. Few fossils have been found to date in this sedimentary succession because lithological conditions are not conducive to their preservation. As a result, there has been a long-term disagreement among geologists about its age. Despite a few lists of fossil names in individual publications, no detailed research on the palaeontology, including palynology, has been reported previously. In this study, we recovered many pollen grains and spores from two samples that were collected on the northern slope of Fenghuo Mountain. They indicate an age no younger than Maastrichtian for the upper part of the Fenghuoshan Group. It is considered likely that the entire Fenghuoshan Group represents deposition between the late Early Cretaceous (possibly Albian) and the Maastrichtian. The palynoflora consists mainly of angiosperm pollen, gymnosperm pollen and fern and bryophyte spores being subordinate. Pollen grains referable to the Ephedrales and the Taxaceae-Cupressaceae groups dominate the assemblage, implying a warm, arid climate and subtropical forest-shrub vegetation at the time of deposition.