为了租地和钻井的需求，他们对比了一个或更多的关键标志层。
One or more key marker beds were identified for the purpose of leasing and drilling.
然后，结合传统的标志层法、煤岩学及古生物学方法，对该区主要煤层进行对比。
Later in the paper, a correlation between the main coal-seams in this province is made, in combination with the traditional method of the key bed, coal petrography and palaeontology.
通过区域对比标志层、野外踏勘资料及层序界面的确定，对研究区延长组进行地层划分。
By the primary marks of contrast in region, data of reconnaissance in field and interface of sequence stratigraphy, stratum of the oil-containing interval Yanchang formation were devised.
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