A number of sandstone-type uranium deposits have been found in the Lower Cretaceous Saihan Formation of Erlian Ba-sin. The segmentation of the Saihan Formation has impact on exploration to some extent. Core observation, logging, seismic profile and comprehensive core documentation show that the Saihan Formation can be divided into four intervals, i.e., Ⅰ(K1bs1),Ⅱ(K1bs2),Ⅲ(K1bs3) and Ⅳ(K1bs4). K1bs1 consists of variegated coarse-grained clastic rocks deposited in alluvial fan. K1bs2 consists of gray or dark gray or dark mudstones and coal beds deposited in swamps and muddy lakes. K1bs3 consists of gray coarse-grained clastic rocks like conglomeratic sandstones deposited in a braided river environment. K1bs4 consists of yellow sandstones interbedded with red mud-stones deposited in a meandering river environment. The target layer for sandstone-type uranium mineralization is interval Ⅲ in the Manitesubbasin and intervalⅣin the Wulanchabusub basin. No uranium mineralization has been discovered in intervalⅠand Ⅱ up till now.%近年在内蒙古二连盆地赛汉组中找到了可观的砂岩型铀矿资源.关于早白垩世赛汉组的分段没有统一的认识,严重影响了铀矿勘查工作的布置.利用石油、煤炭和核工业部门勘查钻孔岩性、测井曲线、综合编录、地震剖面等资料,结合古气候-颜色变化、沉积序列变化反映的沉积环境,将赛汉组划分为4段.赛汉组一段,主要为一套冲积扇(或扇三角洲)环境下的杂色粗碎屑岩组合.二段为一套凹陷中心灰色、黑色湖沼环境下的泥岩夹褐煤层,凹陷边缘为杂色扇三角洲粗碎屑岩,总体以黑色岩系组合为特征.三段为一套灰色、深灰色含砾粗砂岩、砂岩,侧向联通性较好的灰色岩系组合,形成于辫状河环境.四段为一套红色、黄色泥岩与砂岩互层的红色岩系或组合,沉积于曲流河环境.二连盆地马尼特坳陷中砂岩型铀矿形成于三段中,为侧向氧化成矿作用所致;而乌兰察布坳陷铀矿化定位于四段中,为垂向潜水氧化成矿作用所造成,一段和二段目前还没有找到有价值的铀矿化.
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