文中研究报道产自川西松潘县红土坡的中新统马拉墩组孢子花粉植物群。迄今为止，人们关于青藏高原东北边缘新近纪古植被的所知甚少。红土坡马拉墩组孢粉组合的总体特征是榆科（Ulmaceae）、桦木科（Betulaceae）以及松科（Pinaceae）花粉比较丰富，蕨类孢子稀少。被子植物花粉在整个组合中含量最高，占孢粉总数的52.4%—84.4%；其次是裸子植物花粉，占13.8%—44.1%；蕨类孢子仅占1.2%—5.1%。被子植物中以榆科和桦木科花粉最多。榆科花粉可达孢粉总数的14.7%—28.8%，其中绝大多数是榆属（Ulmus），其他可能包括少许榉属（Zelkova）。桦木科花粉含量也很高，达12.6%—25.7%，主要为桦木属（Betula）和桤木属（Alnus）。此外，杨柳科（Salixaceae）、山毛榉科（Fagaceae）以及胡桃科（Juglandaceae）也有一定含量。这样的孢粉组合代表了以落叶阔叶树为主的针阔叶混交林。与此组成相同或相近的森林在我国现代落叶阔叶林或针阔叶混交林植被中很难见到。根据和同期与红土坡纬度相当地区的孢粉组合的对比，推测在早中新世当地的海拔高度已经超过1000 m，甚至达到2000 m左右，也即已经接近或仅略低于当地现今的高度。

Up to now, little is known about the palaeovegetation of the most northeastern part of the great Qinghai-Xizang (Tibet) Plateau during the Neogene time. In this study, we report Miocene pollen and spore assemblages from the Maladun Formation at Hongtupo, a small mountain about 50 km southwest of Songpan County town, Sichuan Province. The palynoflora is characterized by rich presence of Ulmaceae, Betulaceae and abundant Pinaceae pollen with rare spores. Angiosperm pollen occupies 52.9%–84.4% of the total tally. Gymnosperm pollen form 13.8%–44.1% of total pollen and spores. Spores only amount to 1.9%–5.1% of the total assemblage. Other elements in the pollen flora include common Fagaceae (Quercus, Castanea), Salix, Juglandaceae (Juglans, Carya) and minor Liquidambar, Sporotrapoidites, Lonicera, Ephedra, Compositae (Asteraceae), Rosaceae, Leguminosae (Fabaceae), Polygonaceae, Ranunculaceae, Lythraceae etc. Such a pollen flora represents a mixed broadleaved and conifer forest. The pollen flora of the Hongtupo is of late Early Miocene to early Middle-Miocene age based on the correlation with the similar pollen assemblage from the Lengshuigou Formation of Weihe Basin which was dated by the associated vertebrate fossils. The palaeoclimate derived from the pollen flora should be of cold temperate to temperate with an annual temperature of about 8℃–13℃. The present pollen flora shows a much less warm appearance than those of the similar age pollen floras from northern and eastern China, which leads to a deduction of palaeoaltitude at the fossil locality of over 1000 m to about 2000 m above sea level. It is interesting that the pollen flora also contains some warm-loving elements such as Liquidambar and Juglandaceae pollen, which probably implies the Miocene Hongtupo area was neighbored by a low terrace or valley landscape.

中国科学院战略性先导科技专项（XDB26000000、XDA2007020203）和第二次青藏高原综合科学考察项目 （2019QZKK0706）联合资助。