百色盆地渐新世古植被与古气候

为恢复百色盆地渐新世古植被面貌并重建古气候, 对该盆地伏平组孢粉化石进行了采样、分析、鉴定, 共获得孢粉化石34属, 并划分为2个组合: (Ⅰ) Abietineaepollenites-Quercoidites-Polypodiaceaesporites组合; (Ⅱ) Abietineaepollenites-Pinuspollenites-Pediastrum组合。组合Ⅰ时代为渐新世Rupelian中期; 组合Ⅱ时代为渐新世Rupelian晚期至Chattian早期。植被面貌变化为: 针阔混交林, 底部生长着蕨类植被→针叶林。通过孢粉组合属性特征的研究得出孢粉组合Ⅰ代表了亚热带湿润性气候, 湿度相对较大; 孢粉组合Ⅱ代表了亚热带较湿润性气候。通过共存因子分析得出: 在渐新世Rupelian中期至Chattian早期时间段内百色盆地年均降雨量(MAP)在797.5~1 293.7 mm之间, 年均温度(MAT)在11.3~22.6℃之间, 为北亚热带气候特征。而现在的百色盆地位于南亚热带(年均温度: 22.0℃, 年均降雨量: 1 070.5 mm), 二者的差异可能与新生代印度板块与亚洲板块碰撞所造成的亚洲板块"右旋"有关。 

Paleovegetation and paleoclimate in the Baise Basin during Oligocene

To reconstruct the palaeovegetation and palaeoclimate in the Baise Basin during the Oligocene, in this work, we analyzed sporopollen fossils from the Fuping Formation in this region. Thirty-four genera sporopollen fossils are found and divided into two assemblages: (Ⅰ) Abietineaepollenites-Quercoidites-Polypodiaceaesporites Assemblage and (Ⅱ) Abietineaepollenites-Pinuspollenites-Pediastrum Assemblage. The age of assemblage Ⅰ and Ⅱ are mid-Rupelian to Oligocene, and late-Rupelian to early-Chattian to Oligocene, respectively. The paleovegetation changed from conifer-broad leaf forest with fern vegetation growing at the bottom to coniferous forest. Through the study of the characteristics of the palynological assemblages, assemblage Ⅰ represents a subtropical humid climate condition with relatively high humidity, while assemblage Ⅱ represents a humid climate condition in the subtropical zone. The coexistence approach of the nearest living relatives of the palynomorphs shows that during the period of the mid-Rupelian to the early Chattian of the Oligocene, the mean annual precipitation (MAP) was 797.5-1 293.7 mm, and the mean annual temperature (MAT) was 11.3-22.6℃ in the Baise Basin. The characteristics of this basin were a northern subtropical climate during the mid-Rupelian to the early Chattian. However, the present Baise Basin is located in the southern subtropics(MAT: 22.0℃, MAP: 1 070.5 mm). The difference between the Oligocene and today may be related to the "right-rotation" of the Asian Plate caused by the collision between the Cenozoic Indian Plate and the Asian Plate.