These provide base for the correct measurement and valuing of graptolite reflectivity.
从而为笔石反射率的正确测定和取值奠定了基础.
The black graptolite shale facies indicate a deep - water, half enclosed and anoxic sedimentary environment.
中奥陶世黑色的笔石页岩为典型的半封闭缺氧的深水沉积环境,反映了海水逐步加深,水体也变得相对宁静.