作 者 ：GENG Bao-Yin, TA0 Jun-Rong, XIE Guang-Pu
期 刊 ：植物分类学报 2001年 2期
Keywords:Oligocene, Fossil plants, Paleoclimate, Lanzhou Basin,
Abstract:
Fossil plants from the lower part of Xianshuihe Formation in the Lanzhou Basin, Gansu
Province were studied. The flora contains 29 species, representing 20 genera and 12 families, which
include Lauraceae ( Daphnogene ), Lardizabalaceae ( Akebia ), Berberidaceae ( Berberis ), Ulmaceae
( Planera, Ulmus, Zelkova ), Betulaceae ( Alnus, Carpinus ), Myricaceae( Myrica ), Salicaceae
( Populus, Salix), Myrsinaceae(Ardisia), Rosaceae ( Prunus, Sorbus, Sorbaria, Spiraea ), Le-
guminosae ( Gleditsia, Sophora), Anacardiaceae (Rhus), Caprifoliaceae(Viburnum). An analysis
of the floristic elements and their foliar physiognomy shows that most members of the flora are decid-
uous broad-leaved trees or shrubs with a few evergreen shrubs. The most noteworthy species is Rhus
turcomanica which was present in the Middle Eocene to Late Eocene of Central Asia (Kazakhstan,
Turkmenistan). Generally, Rhus turcomanica occurred at the same beds as Palibinia, an extinct
fossil plant whose presence indicates a subtropical dry climate. Another species, Sorbaria callicomi-
folia Kornilova was present from the Early Oligocene to Early Miocene of Central Asia (Kazakhstan
and Turkmenistan). According to an analysis of spores and pollen, this flora contains over 20 spe-
cies. It is predominated by the angiosperm pollen. There appeared Ephedripites and Nitrariadites
which were important elements in the dry area. Ephedripites was found from the Upper Cretaceous to
Early Tertiary. Nitrariadites occurred in the Late Miocene, whereas Rhus turcomanica and Sorbaria
callicomifolia were both reported in the subtropical dry area from the Middle Eocene to Early Oligo-
cene. The latest record of Rhus turcomanica is from the Middle Eocene to Early Oligocene of Central
Asia. The presence of this element in the lower part of Xianshuihe Formation may indicate that its
age is the latest stage of the Early Oligocene.