冀中坳陷饶阳凹陷中北部古近纪沙河街组古生态分析

基于对冀中坳陷饶阳凹陷中北部42口井孢粉化石的鉴定,讨论了该区沙河街组孢粉植物群的古生态分类,建立了一个Quercoidites-Ulmipollenites高比例组合和5个亚组合:Ephedripites-Ulmoideipites亚组合,Pinaceae-Ephedripites-Podocarpidites亚组合,Ephedripites-Pinaceae-Labitricolpites亚组合,Pinaceae-Podocarpidites亚组合和Piceaepollenites-Ephedripites-Cedripites亚组合。通过与黄骅坳陷滩海沙河街组孢粉组合对比,根据研究区各时期孢粉组合的不同特征,探讨了饶阳凹陷中北部古近纪沙河街组古生态的变化。结果表明:研究区各孢粉组合中生组分比例稳定,平均70%以上,而旱生和湿生孢粉组分比例变化细微;沙四段晚期植被类型以常绿—落叶阔叶林为主,属半干旱暖温带气候;沙三段植被类型以针叶林为主,阔叶林混生,属半湿润亚热带气候;沙二段植被类型是针叶混交林,属半干旱亚热带气候;沙一段植被类型以针叶混交林为主,湿生草本植被增多,属湿润亚热带气候。

Palaeoecological Analysis of Paleogene Shahejie Formation in North Central Raoyang Sag of Central Hebei Depression

According to the identification of sporopollen fossils from the 42 wells in north central Raoyang Sag, Central Hebei Depression, the palaeoecological classification of palynoflora in Shahejie Formation was discussed; one palynological assemblage with high proportion of Quercoidites-Ulmipollenites was recognized, and five sub-assemblages were established, including Ephedripites-Ulmoideipites sub-assemblages, Pinaceae-Ephedripites-Podocarpidites sub-assemblages, Ephedripites-Pinaceae-Labitricolpites sub-assemblages, Pinaceae-Podocarpidites sub-assemblages and Piceaepollenites-Ephedripites-Cedripites sub-assemblages. Contrast to the palynological assemblage of offshore Shahejie Formation in Huanghua Depression, the palaeoecological change of Shahejie Formation in north central Raoyang Sag was discussed according to the different characteristics of palynological assemblage during various periods. The results showed that the proportion of mesic sporopollen was stable, with an average of 70% or higher, while there was a little change for the proportion of xerophilous and hygrophilous sporopollen; vegetation pattern during the late member 4 of Shahejie Formation was mainly evergreen and deciduous broad-leaved forest in semi-arid warm temperate climate; vegetation pattern during the member 3 of Shahejie Formation was mainly coniferous forest, and secondly broad-leaved forest in sub-humid sub-tropical climate; vegetation pattern during the member 2 of Shahejie Formation was mainly coniferous and broad-leaf forest in semi-arid sub-tropical climate; vegetation pattern during the member 1 of Shahejie Formation was mainly coniferous and broad-leaf forest with an increase of hygrophilous herbaceous vegetation in humid sub-tropical climate.