松辽盆地白垩系营城组火山岩喷发旋回划分

VOLCANIC ERUPTION CYCLES OF THE CRETACEOUS YINGCHENG FORMATION IN THE SONGLIAO BASIN

鉴于松辽盆地白垩纪营城组火山活动多中心、多旋回、火山物质运动方向多变、成分复杂等特征,依据火山旋回的三个基本要素,即共生序列、内在规律的外部结构表现、同源性,着重考虑对储层研究的指导作用,采用"组内划段—段内划旋回—旋回内划期次"的方案,定义火山旋回为火山活动强度由平静到强烈再到平静而构成的喷发周期内形成的一套火山岩组合,由一系列具有同源性的火山岩构成。一个至若干个期次构成一个旋回,岩性演化具方向性:从基性→中性→酸性的连续变化或其中部分连续变化,相序上呈周期性演变。经大量盆内钻井和盆缘剖面资料研究,将营城组一段和三段分别划分出3个火山喷发旋回。

Volcanic activities recorded in the Cretaceous Yingcheng Formation in the Songliao Basin are characterized by multiple eruption centers, multiple eruption cycles, and complex and variable volcanic lithologies. On the basis of volcanic sequence and assemblage, volcanic eruption cycles in the Yingcheng Formation in the Songliao Basin are inferred to represent variations in the intensity of volcanic activity （e. g. , from quiet to intense and then to quiet）. An eruption cycle consists of one or several eruption stages. Furthermore, lithologic evolution during an eruption cycle is directional, basic to intermediate and then to acidic. Analysis of drill cores and field sections shows that the Member 1 K1y^1） and Member 3（ K1y^3 of Yingcheng Formation each consist of three volcanic eruption cycles.