Abstract: Early Cretaceous Tugulu formation, which widely exposed in the southern and northern basin to the Hala'alt Mountain, was newly discovered in the Hala'alt mountain area. The formation overlaps unconformably on the Pre-Cretaceous strata and the unconformity surface is gentle. The Tugulu formation has nearly horizontal attitude, clear bedding and very simple structure, without any deformation and metamorphism, while its underlying lower Permain or earlier strata are strongly folded deformation with fractures, joints and other structures. The differences are extremely significant. Eroded before Cretaceous but not flattened, Hala'alt Mountain can be regarded as boundary mountain between Hoxtolgay basin and Junggar basin. The difference of mineralization between northern coal and southern oil to the Hala'alt Mountain may be related with such structural framework. Till the early Cretaceous period, Hoxtolgay basin and Junggar basin collided and developed into a unified basin. The discovery of Tugulu formation in the Hala'alt mountain area provides an important evidence for such structural event. Nowadays, the landform pattern of basin-mountain-basin is the product of inconsistent inland uplift.