鄂尔多斯盆地西南部甘肃西峰地区延长组孢粉组合及古气候研究

鄂尔多斯盆地西南部西峰油田中上三叠统延长组长8段和长7段钻井岩心中发现丰富的孢粉化石,分别命名为Aratisporites-Punctatisporites组合和Asseretospora-Walchiites组合,组合特征分别与盆地东南部发现的铜川组孢粉组合和延长组孢粉组合相似,地质时代分别为中三叠世晚期Ladinian期与晚三叠世早期Carnian期。通过孢粉植物群类型地层分布特征及其生态环境讨论,推测盆地区中晚三叠世气候温暖潮湿,雨量充沛,植被茂盛。孢粉植物群所反映的古气候为温带—亚热带暖湿或湿热气候。这是由于本地区当时处于较低的纬度,且濒临大型湖泊,而长8—长7段沉积时期正处于湖泊扩张的鼎盛期。

SPORO-POLLEN ASSEMBLAGES AND PALEOCLIMATE OF THE YANCHANG FORMATION IN THE XIFENG AREA,SOUTHWESTERN ORDOS BASIN,GANSU PROVINCE,NW CHINA

Abundant sporo-pollen fossils were found in cores from the Chang 8and Chang 7members of the Yanchang Formation in the southwestern Ordos basin,NW China.The assemblage of Chang 8member was denominated by Aratisporites-Punctatisporites,and the assemblage of Chang 7member as Asseretospora-Walchiites.Their characteristics are similar to those of the assemblages of the Tongchuan Formation and the Yanchang Formation in the southeast Ordos basin,respectively.Their geological ages are Ladinian of late Middle Triassic and Carnian of early Late Triassic respectively.The sporo-pollen and their ecological distributions in these members suggest the paleoclimate of the eastern Gansu Province in the Middle and Late Triassic was warm and wet,under a temperate to subtropical zone.The wetter paleoenvironment during the Chang 8and Chang 7sections deposited in eastern Gansu Province was due to its proximity to a large lake when a large-scale lake transgression was happening,with the largest lake range.