广西宁明盆地第三纪孢粉植物群及其地层意义

对宁明县城西北南宁至凭祥公路旁第三纪邕宁群露头剖面进行孢粉研究 ,所揭示的孢粉组合中 ,被子植物花粉以壳斗科、桦木科、金缕梅科、榆科和胡桃科为主 ,并零星分布草本植物花粉 ,包括蓼科的蓼粉属、毛茛科的毛茛粉属和菊科的刺面三孔沟粉属等分子 ;裸子植物花粉以松科为主 ,杉科其次 ,松科主要是双束松粉属和单束松粉属 ,雪松粉属连续分布 ,云杉粉属在剖面的中下部连续出现、上部消失 ,铁杉粉属和油杉粉属少量断续分布 ,还见有罗汉松科罗汉松粉属的连续少量分布 ,以及个别的麻黄科麻黄粉属分子 ;蕨类植物孢子零星。对区内地层与孢粉资料作综合对比 ,认为本孢粉组合所指示的地层时代为渐新世。因宁明盆地邕宁群底部以往的孢粉资料反映晚始新世特征 ,推测该盆地第三纪地层的时代至少为晚始新世—渐新世。

TERTIARY PALYNOSTRATIGRAPHY OF THE NINGMING BASIN, GUANGXI

Palynostratigraphical study was carried out on the Tertiary profile (Fig. 1) by the roadside at NW Ningming County, Guangxi Province. Pollen assemblage is characterized by angiospermous pollen mainly including Fagaceae, Betulaceae, Hamamelidaceae, Ulmaceae, Juglandaceae, etc., along with some sporadic herbaceous pollen, such as Polygonaceae, Ranunculaceae, Echitricolporites (Compositae), etc. There are mainly Pinaceae ( Pinuspollenites, Abietineaepollenites, Cedripites, Piceaepollenites, Keteleeriaepollenites, Tsugaepollenites) , Taxodiaceae, and some Podocarpaceae and sporadic Ephedraceae among the gymnospermous pollen, and a few Polypodiaceaesporites, Polypodiisporites and Lygodiumsporites among the pteridophyte spores (Fig. 2). After a comprehensive comparison of the pollen data in some neighboring areas, the current pollen assemblage is assigned an Oligocene in age. It is deduced that the Tertiary strata in the Ningming Basin are at least of Late Eocene-Oligocene in age based on the combined pollen datum of the former study in the basin.