Sedimentary Characteristics and Sequence Framework of Intracontinental Foreland Basin in theWestern China

Key words: 
• intracontinental foreland basin /
• sedimentary characteristics /
• sedimentary sequence /
• superposition style /
• sequence framework

Abstract: Located in the area between orogenic belt and craton, intracontinental foreland basin in Western China was formed by the intracontinental fold-thrust movement resulted from the long-distance effect of plate collision. Without marine source rocks and marine molasses that are always developed along the passive continentalmargin, the intracontinental foreland basin is different from the typical foreland basin in foreign countries to some extent. With abundant hydrocarbon resources, the intracontinental foreland basin has attracted increasing attention of petroleum geologists in recent years. Main differences between intracontinental foreland basin and typ ical foreland basin have been analyzed and main sedimentary characteristics of the intracontinental foreland basin have been proposed. During the fold-faulting episode, the superposition of coarse-grained sediments could form apron-shaped sedimentary body. While during the inactive period of the fold-thrustmovement, the well-developed coal bed andmudstone could form source rocks of high quality. However, during the whole process, the migration of depression center and the excursion between dep ression center and deposition center are common. According to the superposition style of deposits, the intracontinental foreland basin has been subdivided into step-forward, superposition and step-backward types and sedimentary sequence model for each type has been established. Finally, the hydrocarbon generation, accumulation and preservation condition of each type of basin have been discussed, which will be helpful to the hydrocarbon exp loration according to their respective sequence model and to the improvement of exploration efficiency.