云南新生代孢粉组合与气候环境演变

Cenozoic palynological assemblages and their relations with climate-environment evolution in Yunnan

  • 摘要: 新生代全球的气候与植被经历了显著变化。系统开展云南新生代植被与气候的研究将为理解青藏高原隆升和印度季风起源与演化提供重要的信息。总结了近几十年来云南的新生代孢粉记录,重建了除始新世以外的云南新生代植被与气候的大致变化,并划分出9个孢粉组合带:古新世为榆粉属-麻黄粉属-希指蕨孢组合,植被是以落叶阔叶植物为主的常绿落叶阔叶混交林,气候偏干旱; 早中渐新世时为栎粉属-桤木粉属-松科-水龙骨科组合,植被为亚热带常绿阔叶林,气候温暖湿润; 晚渐新世—早中新世针叶林增多,气候有所变凉,为松科-栎粉属-水龙骨科组合; 中中新世为壳斗科-桤木属-水龙骨科-松科组合,壳斗科和喜湿热的蕨类植物含量高,反映了暖湿的中中新世气候环境; 晚中新世—早上新世为壳斗科-松科-桤木属-草本植物组合,早期气候温暖湿润,晚期针叶林和草本植物增多,气候有冷干化趋势; 中上新世为栎属-松科-水龙骨科组合,热带亚热带的科属增加,气候暖湿; 晚上新世为松科-栎属-草本植物组合,针叶林和草本植物扩张,气候有冷干化的趋势; 更新世为松科-草本植物-栎属组合,针叶林和草本植物增多,气候进一步冷干化; 全新世为松科-栎属组合,气候总体回暖,以中期最为暖湿。上述云南孢粉植物群的变化特征揭示了全球温度是控制云南植被长期变化的主要因素,晚渐新世—早中新世的变冷与青藏高原隆升有关,而晚中新世以来的冷干化是全球变冷和高原隆升叠加的结果。已有的研究显示云南古近纪的孢粉研究明显不足,部分地层仍存在时代争议,因此,认为今后在解决地层年代学的基础上,应重点加强云南古近纪孢粉的研究工作。

     

    Abstract: The global climate and vegetation systems have experienced remarkable changes during Cenozoic. The systematic study of the Cenozoic vegetation and climate in Yunnan will also provide some important evidence and information on the uplifting of the Tibetan Plateau in addition to the initiation and evolution of the Indian monsoon. Although the abundant palynological studies have been conducted in recent decades, the systematic and comprehensive researches have not been conducted through the sporopollen in Yunnan. This paper show the comprehensive reviews on the Cenozoic sporopollen records from Yunnan compiled through sporopollen records studied since last four decades and finally reconstructed a 65 Ma record of changing vegetation and climate spanning the whole Cenozoic except for Eocene. The following pollen zones are identified: Ulmipollenites - Ephedripites - Schizaeoisporites zone (Paleocene), the vegetation was composed of mixed evergreen and deciduous broad-leaved forest dominated by deciduous broad-leaved forest, revealing a partial dry climate; Quercoidites-Alnipollenites- Pinaceae-Polypodiaceae zone (Early-middle Oligocene), the vegetation was subtropical evergreen broad-leaved forest, reflecting a warm and wet climate condition; Pinaceae- Quercoidites -Polypodiaceae zone (Late Oligocene-Early Miocene), increasing in coniferous pollen imply a more cooling climate; Fagaceae- Alnus -Polypodiaceae-Pinaceae zone (Middle Miocene), thermophilic taxa percentages were high (Fagaceae, fern), corresponding to the Middle Miocene Climatic Optimum, showing a warm and wet climate condition; Fagaceae-Pinaceae- Alnus -herbaceous pollen zone (Late Miocene-Early Pliocene), a warm and humid climate in early stage, but the expansion of coniferous forest and herbaceous in later stage revealing a cooling and drying trend; Quercus -Pinaceae-Polypodiaceae zone (Middle Pliocene), the tropical and subtropical taxa and their percentages increased, reflecting a warm and wet climate condition; Pinaceae- Quercus -herbaceous pollen zone (Late Pliocene), the expansion of coniferous forest and herbaceous, and the decreasing in the thermophilic percentages (Quercus), implying a cooling and drying trend; Pinaceae-herbaceous pollen- Quercus zone (Pleistocene), coniferous forest and herbaceous expanded more resulting from a further climate deterioration; Pinaceae- Quercus zone (Holocene), the warmest and wettest climate occurred in middle Holocene, corresponding to the Holocene climatic optimum. The palynofloras of Cenozoic in Yunnan thus shows the palaeotemperature as a key factor in controlling long-term trend of vegetation, the cooling in the Late Oligocene-Early Miocene was linked with the uplift of Tibetan Plateau, whereas the cooling and drying since Late Miocene may be the consequence of both the global cooling and the uplift of Tibetan Plateau. However, some problems such as insufficient data on sporopollen records of Paleogene and controversies on the geological ages of some sedimentary formations have remained in Yunnan. Hence, further studies on chronstratigraphy and reconstruction of Paleogene sporopollen in Yunnan are important and required in the future.

     

/

返回文章
返回