The host rock conformably overlies a band of siliceous chertybrecia.

含矿主岩整合地上覆于硅质燧带之上。

Charlotte heard the scrunch of boots on gravel.

夏洛特听到了长筒靴走在路上嘎吱嘎吱的声响。

He had been so absorbed with watching the building that he hadn't heard footsteps on the gravel path.

他留观察那栋建筑，竟没有听见路上的脚步声。