宁夏六盘山地区马东山组孢粉组合特征及其对恐龙生活古气候的指示意义

宁夏六盘山地区早白垩世马东山组河湖相沉积物表面保存有完整的恐龙足迹化石,赋存其中的孢粉是研究恐龙生活时代古气候信息的良好载体。对六盘山地区隆德县前庄村白垩系马东山组蜥脚类恐龙足迹化石赋存剖面进行了系统的孢粉研究,共鉴定出孢粉类型41属63种。剖面自下而上分为Bisaccates-Jiaohepollis、Classopollis-Jiaohepollis-Cicatricosisporites、Cicatricosisporites-Foraminisporis等3个孢粉组合带。孢粉组合特征反映的地质时代为早白垩世Aptian期—Albian期,恐龙足迹化石的建群植被经历了松柏类向掌鳞杉科,再向蕨类植物的转变,进一步研究认为该地区恐龙生活时代古气候经历了亚热带半湿润气候→亚热带温暖半干旱气候→亚热带湿润气候的变化。这与前人对六盘山地区白垩系马东山组沉积古气候环境的研究结论相一致。

Characteristics of Sporopollen Assemblages from Madongshan Formation in Liupanshan Area of Ningxia,China and Their Indicative Significance to the Paleoclimate of the Age of Dinosaurs

Complete dinosaur footprint fossils are preserved on the surface of the fluvial and lacustrine sediments of Early Cretaceous Madongshan Formation in Liupanshan area of Ningxia, and the sporopollen is a good carrier to study the paleoclimate information of the time when dinosaurs lived. A systematic sporopollen study was carried out on the fossil occurrence profile of sauropod dinosaur footprints from Cretaceous Madongshan Formation in Qianzhuang village of Longde county, Liupanshan area. A total of 41 genera and 63 species of sporopollen were identified. It is divided into 3 sporopollen assemblages from bottom to top of the profile, including Bisaccates-Jiaohepollis assemblage, Classopollis-Jiaohepollis-Cicatricosisporites assemblage and Cicatricosisporites-Foraminisporis assemblage. The geological age reflected by the characteristics of the sporopollen assemblage is Early Cretaceous Aptian-Albian period. The established vegetation of dinosaurs footprint fossils has undergone a transition from conifers to cypresses, and then to ferns. Further research suggests that the paleoclimate in the age of dinosaurs experiences a change from subtropical subhumid climate to subtropical warm and semi-arid climate, and then to subtropical humid climate. This is consistent with previous research conclusions on sedimentary paleoclimatic environment of Cretaceous Madongshan Formation in Liupanshan area.