水底喷发的基性熔岩或从陆地流入海中的基性熔岩所形成的一种特殊构造,在陆地的湖河相环境中同样能形成。 熔岩多呈枕状椭球体,也有球状、柱状者,岩枕一般底面较平,顶面上凸呈枕状,其大小不一,直径通常几厘米到几米,以1-2米为多。 我国汉诺坝地区的古近-新近纪陆相玄武岩中就有枕状构造。
水下喷发火山岩典型标志为珍珠岩、玻璃质结构、枕状构造、纹层状凝灰岩和膨润土。
Typical features of subaqueous volcanic rocks include perlite with glassy structure and pillow structure, lamellar tuff, bentonite.
枕状构造是砂层中一组呈“凹”形弯曲的变形沉积体,它的原始层平行于枕状体的底面,顶面则是一个平直的截切面。
Pillow structure consists of a suit of deformed concave upward bodies made of silt and sand whose original layering bent round parallel the basal surface and it truncated at the top surface.
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