A new type of structural association comprising periclinal folds is present in thick-bedded calcareous mudstones and siltstones of the Early Cretaceous Hekou Group in the Lanzhou Basin, NW China. The periclinal fold system consists of meso-scale, open anticlines and synclines with fold axial trends in two perpendicular orientations (NE-SW and NW-SE) and two sets of conjugate thrust faults that form intersections in the same two orientations. Folded and faulted layers of the periclinal fold system are not sedimentary bedding surfaces but sub-parallel curviplanar foliations formed by compaction of the original strata soon after deposition. Many folded curviplanar foliations connect with the unfolded, conjugate thrust faults, indicating that faulting was active during and/or soon after folding. The NE-SW and NW-SE-trending fold axes and fault planes indicate bilateral, subhorizontal contraction acting simultaneously during the formation of the periclinal fold system. In some cases, converging slickenlines on curviplanar foliation planes within anticline cores point to localized isotropic contraction probably caused by scaping fluids and increased hydrostatic pressure. Similarities with the better-known polygonal fault system include development in fine-grained sediments and layer boundness, whereas main differences are a dominance of contractional faults in the periclinal fold system versus extensional faults in the polygonal fault system and a higher consolidation of sediments needed for the development of the periclinal fold system. This study suggests that collision between the Lhasa and Qiangtang Blocks combined with oblique convergence and subsequent collision along the southeastern margin of the Eurasian plate following compaction-related volume loss of fine-grained sediments led to the formation of the periclinal fold system in the Hekou Group in the Late Cretaceous.

兰州盆地早白垩世河口群厚层状钙质泥岩和粉砂岩中存在一种由周斜褶皱组成的新型构造组合。周斜褶皱系统由中尺度、开放的背斜和向斜组成，具有两个垂直方向（NE-SW和NW-SE）的褶皱轴向趋势和两组在相同两个方向上形成交叉的共轭逆冲断层。周斜褶皱系的褶皱和断层不是沉积层理面，而是沉积后不久原始地层压实形成的亚平行曲面叶理。许多折叠的曲面叶理与展开的共轭逆冲断层相连，表明断层在折叠期间和/或折叠后不久是活跃的。NE-SW 和 NW-SE 趋势的褶皱轴和断层面表明在周周褶皱系统形成过程中同时作用的双边、亚水平收缩。在某些情况下，背斜岩心内曲线平面上的会聚滑线表明局部各向同性收缩可能是由溢出的流体和增加的静水压力引起的。与广为人知的多边形断层系统的相似之处包括细粒沉积物的发育和层界性，而主要区别是在周斜褶皱系统中收缩断层与多边形断层系统中的伸展断层相比占优​​势，并且沉积物需要更高的固结周周褶皱系统的发展。