杭东普查区位于鄂尔多斯盆地东胜煤田北部,侏罗系延安组为主要含煤地层,自上而下可划分为3个岩段5个煤组,共含煤8～20层;由于本区处于鄂尔多斯盆地北部边缘附近,延安组沉积时期,沉积环境主要以河流-三角洲相为主,伴有滨湖、浅湖和滨湖-泥炭沼泽相,形成本区相变快、横向上连续性较差、煤层多不稳定的特点;延安组沉积初期,由于聚煤盆地基底的起伏变化,仅在局部地段发育了下部的6煤组,经历了填平补齐之后进入稳定的成煤期,形成多层厚度大、分布广的煤层;延安组顶部地层普遍遭受直罗组砂岩冲刷剥蚀,2煤组仅小范围发育,使延安组形成“下缺上剥”的地质现象.%The East Hanggin prospecting area is situated in the northern part of the Dongsheng coalfield, Ordos Basin. The Jurassic Yanan Formation is the main coal-bearing strata, from top to bottom can be partitioned into 3 lithologic members and 5 coal groups, totally 8 to 20 coal seams. Because of the area is near the north margin of the Ordos Basin, during the Yanan Formation depositional period, the sedimentary environments had mainly fluvial-deltaic facies, associated with lakeshore, shallow lake and lakeshore-peat bog facies thus causing characteristics of quick facies transition, poor continuity laterally and unsteady coal seams. During the initial stages of Yanan Formation deposition, owing to the undulating basement of the coal-accumulation basin, thus the bottom part No.6 coal group was only developed in local sectors. After experienced the filling and leveling up, then come into stable coal-forming stage and has formed thick and widespread coal seams. The top part strata of Yanan Formation were widely scoured and denuded by the Zhiluo Formation sandstone, thus the No.2 coal group was only developed in small sectors and made a geological phenomenon of a " hiatus bottom and denuded top" Yanan Formation.
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