松辽盆地东南隆起区下白垩统营城组三段火山岩岩性、岩相序列

Lithology,Lithofacies and Successions of the Volcanic Rocks of Upper Cretaceous Yingcheng Formation,Southeastern Songliao Basin

通过大比例尺野外岩性岩相填图、掌子面二维岩性岩相描述和详细岩矿鉴定,研究营城组三段内幕。本区营三段自下而上岩性序列表现为2个中基性到中酸性的火山岩旋回:①下部为石英安山岩、安山岩、安山质集块熔岩、安山质集块岩、安山质角砾岩和安山质角砾凝灰岩,向上过渡为砂质凝灰岩和英安质凝灰熔岩;②上部为玄武安山岩和玄武质集块熔岩,向上过渡为英安岩、珍珠岩、英安岩、英安质凝灰熔岩、英安质沉凝灰岩和英安岩。旋回①岩相纵向序列:溢流相下部亚相、火山通道相火山颈亚相、爆发相空落亚相、火山沉积相再搬运亚相、爆发相热碎屑流亚相。旋回②岩相纵向序列:溢流相上部亚相和下部亚相、火山通道相火山颈亚相、溢流相下部亚相、侵出相内带亚相、溢流相下部亚相、爆发相热碎屑流亚相、火山沉积相再搬运亚相、溢流相下部亚相。营三段火山岩发育于松辽盆地断陷末期,是盆地断陷转为坳陷过程的重要岩石记录。

The 3rd member of Yingcheng Formation was detailed studied by large scale mapping of lithology and lithofacies, 2D surveying of small lithology and lithofacies section and identifying rocks. The 3rd member of Yingcheng Formation contains 2 cycles which changed from intermediate-basic rocks to intermediate-acidic rocks： Cycle①changed upward from quartz-andesite, andesite, andesitic agglomeratic lava, andesitic agglomerate, andesitic breccia and andesitic breccia tuff, to sandy tuff, dacitic tuff lava. Cycle② changed from basalticandesite, basalticagglomeraticlavatodacite, dacitic tuff lava, dacitic tuff. The upward vertical lithofacies succession of cycle ①is： lower subfacies of effusive facies, diatreme subfacies of volcanic conduit facies, airfall subfacies of explosive facies , reworked volcanogenic sediments sub facies of volcanogenic sedimentary facies , pyroclastic flow subfacies of explosive face. The upward vertical lithofacies succession for cycle ②is： lower and upper subfacies of effusive facies, diatreme subfacies of volcanic conduit facies, lower subfacies of effusive facies, inner sufacies of intrusive facies, lower subfacies of effusive facies, pyroclastic flow subfacies of explosive facies, reworked volcanogenic sediment subfacies of volcanogenic sediment facies, lower subfacies of effusive facies. The lava in 3rd part of Yingcheng Formation erupted in the late period of fault subsidence and it is the important lithology record of the Songliao Basin＇s transform from a fault subsidence basin to a sag basin.