松科2井早白垩世沙河子组孢粉组合及其古气候意义

Early Cretaceous spore-pollen assemblages from the Shahezi Formation in Well SK-2 and their paleoclimate significance

为探讨黑龙江省安达市松科2井深层(3395.46~3901.35 m)地层的时代特征,分析地史时期的古植被及古气候条件演变,利用孢粉学方法对松科2井进行研究。结果显示,研究井段可划分为Leiotriletes sp.-Cyathidites australis-Chasmatosporites sp.孢粉组合(3832.94~3901.35 m)和Klukisporites triangulus-Aequitriradites sp.-Pristinuspollenites sp.孢粉组合(3395.46~3613.62 m),孢粉组合指示的地质时代为早白垩世欧特里夫期(Hauterivian)—巴列姆期(Barremian)早期,可作为松辽盆地沙河子组上部生物地层学对比的标志;此外,孢粉组合反映的植被类型演化规律是针叶林、灌草丛—常绿阔叶林—针叶林、灌木丛—针阔叶混交林,揭示研究区沙河子组后期气候带演替规律是暖温带—南亚热带—暖温带—温带,气候干湿变化规律为湿润—半湿润—湿润—半湿润。

Well SK-2 is located in the Anda City of Heilongjiang Province,China.A total of 4134.8 m continuous core in Well SK-2 provides a unique chance to study the Lower Cretaceous in the Songliao basin,being an important part in the continental scientific drilling program.Based on the distribution of pollen and spores in the Well SK-2,two assemblages are established for the upper part of the Shahezi Formation.They are named as Leiotriletes sp.-Cyathidites australis-Chasmatosporites sp.assemblage(at the depth of 3832.94~3901.35 m)and Klukisporites triangulus-Aequitriradites sp.-Pristinuspollenites sp.assemblage(at the depth of 3395.46~3493.24 m).The geological age of the Shahezi Formation is assigned to Hauterivian–Early Barremian(Early Cretaceous)according to the characteristics of the assemblages.The reconstructed vegetation changes from coniferous forest and tussock to evergreen broad-leaf forest,to coniferous forest and tussock,and to coniferous and broad-leaved mixed forest during the time interval.The reconstructed climate changes from humid warm temperate to semi-humid south subtropical,to humid warm temperate,and to semi-humid temperate.