TectonicSedimentary Conditions for Development of PreMesozoic Marine Source Rocks in China

Key words: 
• marine sequence

Abstract: The PreMesozoic in China are dominated by marine deposits with multiplelayer series and multipletype source rocks, indicating the huge potential for oil/gas exploration in the marine sequences of China. However, the differential control of tectonic setting and sedimentary background results in significant differences in the quality and distribution of source rocks, thus controls the exploration potential of the marine sequences. During SinianEarly Paleozoic（Z－O2）, the main plates in China were in a tectonicsedimentary period with ocean basin extending and landmass dispersing. Source rocks of passive continental margin slope facies were developed in the peripheries of main landmasses such as Huabei, Yangtze and Tarim. These source rocks feature in wide zonal distribution, extensive distribution, high quality and longterm inheritance development. In the late of Early Paleozoic（O3－S）, ocean basins subducted and China Ancient Land converged and took shape. Under the constraint of uplifts on plate margin, source rocks were mainly developed in intraplatform sags. They are characterized by planar distribution and small thickness. In Late Paleozoicearly Mesozoic（D－T）, North of China was dominated by cratonic tectonic setting where coal measure source rocks of transitional facies were developed. These source rocks feature in planar distribution, large area and gas predominance. In contrast, South of China was dominated by divergent tectonic setting and the Huanan platform split into a tectonic framework of "basin surrounding platform". Source rocks were deposited in the interior of deep faulted depression and are characterized by narrow zonal distribution, high quality and small area.