n. substratum ; understratum
misc. lower segment
成矿物质及介质来源于太华群及下部地层、花岗岩浆和中生代湖盆。
The ore forming material and media came from the strata of the Taihua Group and its lower strata, the granite magma and Mesozoic lake basin.
下部地层以石灰岩、泥页岩、砂岩为主，地层疏松，易漏失，属低压高产地层。
The lower formation is consisted of loose limestone, shale and sandstone, with low formation pressure coefficient.
平顶山二矿含煤地层山西组下部地层的沉积环境为潮坪，上部是三角洲体系的产物。
In No. 2 Coal Mine of Pingdingshan, the sedimentary environment of the lower stratum of Shanxi formation is considered as the tidal plat and the upper stratum and the result of delta systems.
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