Abstract: The Shichang Zhonglou basin is situated in the Yihe Shuhe area at the middle section of the Tan Lu fault zone The strike slip Tan Lu fault cuts the Qinling Dabie Jiaonan orogen of Pre Mesozoic,while in the study area the Yihe Shuhe (Yi-Shu) fault overlies the north margin shear zone of the Jiaonan orogen,which gives out an ⁴⁰Ar/³⁹Ar age of 136.2 Ma The faults are unconformably covered with the Qingshan Group of the age of 119 Ma (K-Ar whole rock) These evidence show that the Tan Lu fault had significant strike slip movement The Shichang Zhonglou basin is controlled by the Yihe Shuhe fault,it occurs as a rhombachasm tectonic basin with a length 60 km and a width 30 km The thickness of the Early Cretaceous Laiyang Group in the basin is more than 6263.7m The sedimentation rate is greater than 0.4mm/a The fast changing sedimentary facies in the Laiyang Group reflects that the basin was narrow and deep Migration of the sedimentation center is consistent with the strike slip boundary faults showing the characteristics of "depositing while strike slip moving" It is suggested that the Shichang Zhonglou basin is a pull apart basin formed during the process of sinistrial strike slip movement of the Tan Lu fault zone in early Cretaceous

Key words: Tancheng Lujiang fault zone, Active fault, Pull apart basin, Early Cretaceous

摘要： 石场-中楼盆地位于郯庐断裂带中段的沂河-沭河地区。郯庐断裂左旋切割了秦岭-大别-胶南造山带及前中生代地层,研究区内沂河-沭河断裂切割了年龄为136.2Ma(⁴⁰Ar/³⁹Ar法)的胶南造山带北缘剪切带,并被时代为119Ma(K-Ar法)的青山群地层不整合覆盖,显示郯庐断裂在早白垩世曾发生了明显的走滑运动。石场-中楼盆地受沂河-沭河断裂的控制,整体为长60km、宽30km,长宽比近于2∶1的"菱型"构造盆地。盆地内早白垩世莱阳群的沉积厚度大于6263.71m,沉积速率大于0.4mm/a;沉积相特征反映盆地具有深而窄,沉积速度快、沉积相变剧烈的特点。盆地沉积中心的迁移方向与边界断裂的左旋走滑效应一致,"边走滑边沉积"的特征明显。根据构造背景、构造格架及沉积特征,确定石场-中楼盆地为郯庐断裂早白垩世左旋走滑过程中形成的拉分盆地。

关键词: 郯庐断裂带, 活断层, 拉分盆地, 早白垩世