河北省围场县北部山湾子盆地古风化壳对大北沟组地层划分的意义  

Paleo-weathering crust significance for the Dabeigou formation division in Shanwanzi basin, Beishan area, Heibei province

作　　者：邓绍颖 吴洋[1] 邓雯[1] 王艳凯[1] 申晋青 李丰[1] 

机构地区：[1]河北省区域地质矿产调查研究所,河北廊坊065000

出　　处：《地质调查与研究》2017年第2期119-125,共7页Geological Survey and Research

基　　金：国家地质调查项目"晋冀成矿带地质矿产调查(1212011220488)"

摘　　要：通过1/5万区域地质调查,笔者在围场县北部山湾子盆地张家口组顶部发现古风化壳,风化壳由张家口组顶部酸偏碱性火山岩风化残积形成,灰紫、紫红色,厚5~100 cm,延伸较稳定,长约30 km,垂直分带特征明显,上部为强风化的残积层,结构疏松,残积碎石颗粒较小,粘土矿物占比较高;下部为半风化层,主要由残积碎石组成,原岩结构、构造特征保存较完好,底部风化强度较弱,碎石间仍断续相连,与下伏基岩呈渐变过渡,风化壳的存在,表明大北沟组与下伏张家口组之间存在明显间断,我们将其确定为大北沟组底界,解决了以往区内张家口组与大北沟组界线位置不易确定及划分比较混乱的问题。山湾子盆地半壁山河南大北沟组剖面顶底齐全,化石丰富,接触关系清楚,无疑是研究大北沟组较为理想的场所之一。笔者等对围场北部山湾子盆地大北沟组进行了划分对比研究,为区域上大北沟组的研究及大北沟组与张家口组界线的划分具有借鉴意义。During the 1/50 000 scale regional survey, we discovered a paled-weathering crust in the upper of the Zhangjiakou formation in the Shanwanzi basin in the north of Weichang County, Heibei province. The paled- weathering crust is formed by weathering residual acid alkaline volcanic rocks with colour purple or purple red, thick 5 - 100 cm, more stable extension, about 30 km,vertical zoning characteristics. The upper part is a strong weathering residual layer, the structure is loose, the residual gravel particles are smaller and the clay minerals are relatively high. The lower part is a semi-weathered layer that is mainly composed of residual crushed stone, the structure of the original rock is well preserved, the weathering intensity is weak at the bottom, and the gravel is still intermittently connected and the underlying bedrock gradual transition. The weathering crust shows that there is a obvious discontinuity between the Dabeigou formation and the underlying Zhangjiakou formation. We identified it as the bottom boundary of the Dabeigou formation that has solved the problem of the boundary between Dabeigou formation and Zhangjiakou formation. We also studied the classification and correlation of the Dabeigou formation in the Shanwanzi basin in the north of Weichang area for giving some inspiration to Lhe follow-up work.

关 键 词：围场 山湾子盆地 古风化壳 大北沟组 划分对比 

分 类 号：P534.53[天文地球—古生物学与地层学]